UNCORRECTED PROOF
The carboniferous of the Western Karakoram (Pakistan)
M. Gaetania,*, A. Zanchib, L. Angiolinia, G. Olivinia, D. Sciunnachc, H. Bruntond,A. Nicoraa, R. Mawsone
aDipartimento di Scienze della Terra, Universita di Milano, Via Mangiagalli 34, Milano 20133, ItalybDipartimento dell’Ambiente e del Territorio, Universita di Milano-Bicocca, Piazza della Scienza 4, Milano 20126, Italy
cRegione Lombardia, Struttura Analisi e Informazioni Territoriali, Piazza Duca d’Aosta 4, Milano 20124, ItalydDepartment of Palaeontology, The Natural History Museum, South Kensington, London SW7 5BD, UK
eMacquarie School of Earth Science, Centre for Ecostratigraphy and Paleobiology, North Ride, NSW 2119, Australia
Received 3 December 2002; accepted 13 May 2003
Abstract
The results of the study of the Carboniferous successions in the western part of the Northern Karakoram during three geological
expeditions are summarized here. Rocks of that period are not uniformly preserved in the several thrust sheets forming the Northern
Karakoram. In most of them only the basal part of the Carboniferous, up to the Visean, is preserved, whilst in the Karambar thrust sheet a
more complete section—previously almost unknown—is preserved. Four new lithostratigraphic units, time-constrained by brachiopod and
conodont biostratigraphy, are described, from bottom to top: (1) the Margach Formation: prevailing dark shales with subordinate fine
subarkoses and quartzarenites, up to 300 m thick (mid-Famennian to middle Tournaisian); (2) the Ribat Formation: grey crinoidal limestones
passing upwards to dark marly limestones and marls, at least 300 m thick (middle Tournaisian to Serpukhovian); (3) the Lupsuk Formation:
subarkoses to feldspathic quartzarenites in thick beds, alternating with dark shales and siltstones, up to 400 m thick (Serpukhovian to
uppermost Carboniferous); (4) within the Lupsuk Formation a local member, the Twin Valleys Member, up to 100 m thick, a bioclastic
limestone intercalation of post-Moscovian age, is distinguished. The Carboniferous successions are invariably sealed by the arkoses to
quartzarenites of the Gircha Formation, 133 m above the base of which, in the Karambar area, an Asselian brachiopod fauna was recovered.
The Carboniferous succession is interpreted as recording the evolution of the passive margin of the Northern Karakoram Terrane, from
early rifting stage in the Late Devonian to syn-rift events during the Late Carboniferous. The basal part of the Gircha Formation, of latest
Carboniferous-earliest Permian age, is considered to have been deposited above a break-up unconformity, linked to the early drifting in the
seaway bordering the Karakoram.
In the palaeontological appendix the most significant brachiopod taxa (19 species, one new) are described.
q 2003 Published by Elsevier Ltd.
Keywords: Carboniferous; Palaeo-Mesozoic sedimentary rock; Western Karakoram; Pakistan
1. Introduction
The Karakoram Block consists of four major structural
elements. From south to north they are: the Southern
Metamorphic Belt; the Karakoram Batholith, separated in
the western part of the range by the Metasedimentary
Intermediate Belt; and the Northern Karakoram Terrane,
consisting of crystalline and Palaeo-Mesozoic sedimentary
rocks (Figs. 1 and 2). The absence of a major metamorphic
imprint in the North Karakoram allows us to recognize the
Carboniferous sedimentary successions.
The first reconnaissance expedition to this area failed to
find evidence of Carboniferous rocks (Hayden, 1914; Tipper
in Pascoe, 1924; Talent et al., 1982). In the report of our
1992 expedition (Gaetani et al., 1996) we inferred the
existence of the Lower Carboniferous on the basis of
stratigraphic relationships, but were unable to date the
succession correctly through its palaeontological content.
The first consistent evidence of Carboniferous fossils was
obtained during the 1996 field expedition, especially in the
area around Karambar Lake (Angiolini et al., 1999).
Therefore in the 1999 expedition, additional logging and
sampling was undertaken throughout the area by Zanchi
and Gaetani. Geological field reconnaissance during the
1990s, in the previously almost geologically unknown
1367-9120/03/$ - see front matter q 2003 Published by Elsevier Ltd.
doi:10.1016/S1367-9120(03)00137-8
Journal of Asian Earth Sciences xx (0000) xxx–xxx
www.elsevier.com/locate/jseaes
* Corresponding author.
E-mail address: [email protected] (M. Gaetani).
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UNCORRECTED PROOFWestern Karakoram, was carried out by the following
geologists, with the dates in which they participated:
Angiolini (1992, 1996); Gaetani (1992, 1996, 1999); Nicora
(1992); Olivini (1999); and Zanchi (1996, 1999). Angiolini
studied the Carboniferous brachiopods, Nicora and Mawson
the conodonts, and Sciunnach the sandstone petrography.
The aim of the present paper is to illustrate the general
stratigraphic and tectonic setting of the Carboniferous
successions measured and sampled during three
expeditions (1992, 1996, and 1999). Knowledge of the
Carboniferous is critical to understanding the earlier stages
of rifting and drifting of Cimmerian Blocks away from the
Gondwanan margin.
2. Regional geology
The North Karakoram Terrane, as defined in recent
works (Zanchi and Gaetani, 1994; Gaetani et al., 1996;
Zanchi et al., 2000) consists of a thick and polyphase
stack of thrust sheets which lie to the north of the
Karakoram Batholiths (Le Fort and Gaetani, 1998) (Fig. 3).
In the Chitral region, the Karakoram is separated from the
East Hindu Kush-Wakhan by the Tirich Boundary Zone, a
left lateral shear zone including deformed ultramafic
rocks, completely ignored by most previous authors
(Pudsey et al., 1985; Pudsey, 1986; Searle, 1991).
These rocks record the pre-mid-Cretaceous accretion of
the Karakoram Block to the southern Pamir ranges
(Zanchi et al., 2000). East of the Shah Jinali Pass, the
Tirich Boundary Zone is tectonically elided by NE–SW
left-lateral strike-slip faults, and the Late Palaeozoic
Wakhan and Misgar slates of Wakhan, are directly
stacked above the Karakoram units. Large sheets of
Palaeo-Mesozoic carbonates (Atark and Khan Kun Units,
mostly Permian to Jurassic in age) and poorly known
crystalline complexes including Mesozoic intrusives and
older metamorphic rocks cropping out on the Afghanistan
side (e.g. Qal-a-Ust gneisses) are also included within the
East Hindu Kush-Wakhan.
Fig. 1. Structural index map of the Karakoram and surroundings regions, showing the position of Fig. 2. NP: Nanga-Parbat syntaxis; MMT: Main Mantle
Thrust; NS northern suture; RPZ: Rushan-Pshart zone; WABZ: Wanch-Ak Baital zone.
Fig. 2. General tectonic map of Wakhan and Karakoram.
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UNCORRECTED PROOF
To the west, the southern boundary of the North
Karakoram Terrane is generally tectonic and consists of a
high-angle reverse shear zone with oblique and left-lateral
components, passing to a south-dipping north-vergent thrust
plane in the Chiantar glacier area. Slices of the Cretaceous
batholith are tectonically included within the cover, as well
as deformed metasediments which occur along the main
tectonic boundaries among the intrusive units of the
batholith. Intrusive contacts are locally preserved.
The sedimentary cover of the North Karakoram Terrane
includes several thrust sheets showing complex geometrical
relationships and different directions of tectonic transport
(Figs. 2 and 3). A major subdivision is marked by the Reshun
Fault of Chitral (Pudsey et al., 1985; Zanchi et al., 1997;
Zanchi et al., 2000), which connects to the Upper Hunza
Fault in the east, over a distance exceeding 200 km (Fig. 2).
Its occurrence through the Chiantar glacier area is suggested
by thin slices of the Reshun Formation, which may
interfinger with the Tupop Conglomerate around Chillinji.
South of this fault, tectonic units locally include the pre-
Ordovician crystalline basement and Palaeozoic
sediments, with reduced thickness and poor fossil
content (Axial Unit, Dobargar-Kotalkash metasediments,
Garmuth-Chillinji-Guhjal Units). The one exception is
represented by the Chillinji Unit, where an almost complete
Palaeozoic succession, unconformably covering pre-Ordo-
vician intrusives, is exposed (Fig. 3).
Most of these units were affected by a very low to low
grade metamorphism. The Cretaceous Reshun Formation
occurs locally, with an unconformable boundary above these
units, with a thickness varying from a few tens to hundreds of
metres. The southern margin of these units is intruded by the
Cretaceous to Paleogene plutons of the Karakoram Batholith
(Debon et al., 1987; Debon, 1995; Debon and Khan, 1996;
Debon et al., 1966).
No pre-Ordovician rocks occur north of the Reshun
Fault, where Palaeo-Mesozoic sedimentary successions are
exposed, forming a complex stack of thrust sheets laterally
extending usually a few tens of km (Figs. 2 and 3). Most
of the floor thrusts occur within the Ordovician-?Silurian
slates of the Baroghil Group. West of the Baroghil Pass to
Chitral, up to the longitude of Morich, this thrust system is
tectonically bounded by the Tash Kupruk Unit (Gaetani
et al., 1996), which consists of alkali basalts and
associated marbles.
From the eastern Chitral to the upper reaches of the
Karambar River, thrust sheets consist mostly of Palaeozoic
successions, the youngest sediments being Early Jurassic in
age. On the other hand, along the eastern side of the range,
thrust sheets include rocks not older than Permian or
possibly Upper Carboniferous (Gaetani et al., 1990; Zanchi
and Gaetani, 1994). To the east, Carboniferous fossils have
been found only in the Upper Chapursan Valley between
Buattar and the Chillinji Pass in a small thrust sheet along
the Reshun/Upper Hunza fault system.
The Carboniferous successions have been studied in the
Lasht, Baroghil-Lashkargaz, and Karambar Units, the latter
preserving the most thick and complete sections.
Fig. 3. Structural map of Wakhan and Western-Central Karakoram, from Zanchi et al. (2001). Units in legend are organised from north to south. SJ-P: Shah
Jinali Pass; Ba-P: Baroghil Pass; Ka-P: Karambar Pass; Ch-P: Chillinji Pass.
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UNCORRECTED PROOF
To clarify the regional tectonic setting, a more detailed
description focusing on the tectonic units containing
Carboniferous rocks, follows below.
2.1. The Lasht Unit
The Lasht Unit, which crops out around the village
of Lasht along the Yarkhun valley, mainly consists of
Devonian to Permian, and possibly Mesozoic carbonate to
terrigenous successions (Gaetani et al., 1996). E–W
trending folds and faults make the structural setting very
complex, especially in the west, where the unit is intensively
sliced and repeated tectonically. Several stratigraphic
characters of the tectonic unit, i.e. the occurrence of the
Devonian Chilmarabad and Shogram formations, the
Carboniferous limestones, Permian fusulinid limestones,
very similar those of the Chapursan Group (Hunza valley,
Gaetani et al., 1995; Angiolini, 1966), and red beds of the
Gharil Formation make it comparable to the Baroghil-
Lashkargaz Unit (Gaetani et al., 1996). East of Lasht, the
Lasht Unit is tectonically elided by left-lateral NE–SW
trending strike-slip reverse faults which may represent the
eastern continuation of the Reshun Fault.
2.2. The Baroghil-Lashkargaz Unit
The Baroghil-Lashkargaz Unit occurs in the central part
of the study area around the Baroghil Pass and Lashkargaz.
It consists of an almost complete Ordovician to Jurassic
succession (Gaetani et al., 1996; Talent et al., 1999;
Quintavalle et al., 2000) about 4–5 km thick. It is bounded
to the south by the Axial Unit (Gaetani et al., 1996) through
a complex system of reverse-oblique faults, including
conglomerates of the Reshun Formation and intensively
deformed marble slices. The central-southern part of this
unit is little deformed, showing a continuous sedimentary
succession. On the contrary, its northern boundary is
intensively deformed, showing E–W trending overturned
and recumbent folds and south-vergent thrusts, which
cause intensive shortening and tectonic repetition of the
Lower Permian carbonates. The northwestern boundary
with the Karambar Unit along the Chiantar Glacier is also
very complex.
2.3. The Karambar Unit
The Karambar Unit extends north and east of the
Baroghil-Lashkargaz Unit, between the Chiantar Glacier
and southern Wakhan, also occurring largely to the north of
the Afghanistan border. This unit contains the thickest and
most complete Palaeozoic succession of the Karakoram
Range. It includes at the base Ordovician and ?Silurian
slates and quartzarenites (Vidiakot and Yarkun Formations),
and Devonian carbonates (Vanadil and Chilmarabad
Formations, Early to Middle Devonian in age) which are
not discussed in the present paper.
Above these units follow the ?Givetian-Late Devonian
Shogram Formation and the four lithostratigraphic units of
Carboniferous age, which will be described in Section 3.
The most peculiar stratigraphic feature of the Karambar
Unit is this thick Carboniferous succession which crops out
extensively from the Karambar Lake to Afghanistan and
extends westward to the Ribat Valley area.
The Carboniferous units are conformably covered by the
Early Permian Gircha Formation, which exceeds 1000 m in
thickness. As in other areas the Gircha Formation is
tectonically detached from the older units, this succession
represents a unique complete stratigraphic section across the
Late Palaeozoic in Karakoram. The Gircha Formation is
covered by a thick Permian mainly carbonate succession,
well exposed south of Shuinji.
The southern sector of the Karambar Unit is highly
folded and abruptly cut by the Reshun Fault. The eastern
contact with the Sost-Khora Burt Units still is poorly
defined, due to the inaccessibility of the area and the
intrusion of the Chatteboj granite, which partially masks
the original contacts (Fig. 3). The unit is split by a large
NNE–SSW trending tear fault extending from the Chiantar
Glacier to the east of the Karambar Lake, with a left-lateral
lateral throw of some kilometres. The western and the
northern sectors of the Karambar unit show NNW–SSE to
NW–SE trending west-vergent folds and thrusts, whereas
the eastern part shows E–W south-dipping thrust structures.
Although the Chiantar area displays a very complex
structural setting, the sedimentary succession cropping out
along the Ribat valley is generally poorly deformed and
several stratigraphic logs have been recorded.
3. Lithostratigraphy
3.1. The Karambar Unit
Being the best and most complete succession, the
Karambar Unit will be used as a reference section.
The following lithostratigraphic units have been identified
(Fig. 3):
(6) Gircha Formation (?latest Carboniferous–early Sak-
marian)
(5) Twin Valleys Member (Moscovian-?)
(4) Lupsuk Formation (Serpukhovian–Moscovian)
(3) Ribat Formation (late Tournaisian–Bashkirian)
(2) Margach Formation (mid-Famennian–middle Tour-
naisian)
(1) Shogram Formation (mid-Givetian–mid-Famennian).
3.1.1. The Shogram Formation (Desio, 1966)
This unit, up to 240 m thick, is briefly discussed here as it
forms the base of the Carboniferous succession. The basal
tens of metres consist of conglomerates and arenites, mostly
deposited in a fluvial environment, overlain by alternating
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UNCORRECTED PROOF
fine sandstones and cocquinoid layers, commonly rich in
brachiopods. One distinctive feature is the presence of one
or two grey calcareous horizons of bafflestone, a few tens of
metres thick, packed with colonial corals. This is a
prominent feature in the lansdscape and allows easy
correlations. Upwards, the carbonate content gradually
decreases and the definition of the upper boundary depends
on the quality of the outcrops. Along the Ribat valley
section the boundary with the overlying unit is defined by
the appearance of thick and laterally continuous packages
of dark grey siltstones, with subordinate intercalations of
fine-grained arenites, and negligible calcareous beds.
3.1.2. The Margach Formation (new name)
Between the alternating calcareous/arenaceous rocks of
the Shogram Formation and the crinoidal limestones of the
Ribat Formation, a terrigenous unit, consisting mostly of
dark grey to black siltstones and shales, crops out
extensively. The name originates from the cattle shelter of
Margach on the north side of the valley. Average thickness
exceeds 200 m, but due to the incompetence of the shales,
this unit is often tectonically laminated.
Three lithozones were distinguished in the Ribat section,
which we identify as the type-section of the unit (Figs. 4
and 5). This section was measured along the slope of
the south side of the valley, at an average altitude of
4550–4650 m above sea level, up to a total thickness
of 294 m. From the base upwards:
(a) Dark grey to dark green splintery siltstones intercalated
with thin-bedded arenites, rarely with parallel
laminations; rare intercalations of bioclastic limestones
bearing brachiopods and crinoid fragments, and a
single 0.5 m-thick bed with Receptaculites (an alga
often called ‘sunflower coral’). Thickness 92 m.
(b) Dark grey to black splintery siltstones and slates, with
bioturbated horizons. Rare arenitic intercalations with
dish-and-pillar structures. Thickness 118 m.
(c) Fine- to very fine-grained arenites in beds 20 to
40 cm thick, locally displaying parallel lamination,
dominate in the lower part, whereas coarser
sandstone beds, also displaying microconglomerate
lags and erosional channels, tend to prevail upwards.
Asymmetric ripple marks indicate progradation from
S to N. Bioturbation is more common in the thinner
bedded arenites; hybrid biocalcarenites and biocal-
cirudites are also present. Thickness 84 m.
Fossil content. The Receptaculites (CK1066) is a new
form (Hubmann, personal communication, 2003) of a group
of enigmatic calcareous structures which appeared in the
Early Ordovician and disappeared in the Early Triassic. No
fossils were discovered in the second lithozone. Instead in
the third lithozone a small brachiopod assemblage with
Parallelora aff. subsuavis (Plodowski, 1968), Rhipidomella
sp., and Rhynchopora sp. was collected in samples CK1073,
CK1074, CK1075, CK1077.
Age: Latest Devonian–?early middle Tournaisian.
Environment. The Margach Formation records sedimen-
tation on a muddy shallow marine flat, with significant
terrigenous input under low energy conditions, and largely
sheltered from the waves. No significant emersion was
detected. The third lithozone marks a general increase in
the energy of tractive currents. Erosional channels and
coarser-grained detritus document a general forestepping of
more proximal facies. The fragmentary fossils belongs to
stenohaline organisms. A shoreface environment with no
significant emersion is inferred.
3.1.3. The Ribat Formation (new name)
This unit is established to characterize the grey to dark-
grey limestones and marls that overlie the Margach
Formation in the Karambar and in the Baroghil/Lashkargaz
tectonic units (Fig. 5). A complete section is difficult to
measure, but this unit may be thicker than 300 m. The type
section follows the type section of the Margach Formation
along the slope of the south side of the Ribat valley (hence
the name of the unit), but is interrupted by the moraine of the
Zoe Glacier, 135 m above the formation base. The unit
reappears on the east side of the glacier above the level we
measured, at about 4900–5000 m. We did not climb this
high. An additional section may be measured on the left side
of the Lupsuk Glacier from 5000 m upwards, at the base of
the ridge forming the Pakistan/Afghanistan border. In the
type section, the basal contact is partially covered. The
lowermost part is characterized by hybrid crinoidal lime-
stones, cross-bedded and with topset laminations,
suggesting a transport direction towards the N–NE (in
present coordinates). Fossils are abundant, with crinoid
ossicles and small fragmentary solitary corals. This basal
interval, 15 m thick, is overlain by grey limestones, in beds
20–40 cm thick, often very rich in crinoid ossicles, locally
graded or with parallel lamination. Marly intercalations may
also occur occasionally. This lithology is rather monotonous
along the section measured, with recurrent facies rich in
crinoid ossicles and, locally, also fragmentary Spiriferide
and Productoid (Dictyoclostid) brachiopods. The Ribat
Formation exhibits significant lateral variation. In the
Lupsuk Glacier area (Figs. 4 and 5) the unit forms the
core of an anticline and the lower exposed part consists of
thick-bedded to massive crinoidal limestones, overlain by
well-bedded crinoidal limestones, with sparse Productoid
and Spiriferide brachiopods. In the Triple Junction section,
above the bedded crinoidal limestone, dark marly lime-
stones, alternating locally with chert and marls, are at least
150 m thick (Figs. 4 and 5). In the lower part, the marls are
locally bioclastic with brachiopods, solitary corals and
trilobites. Also in the Twin Valleys section (Figs. 4 and 5)
grey dark marly limestones are prevalent, whereas bioclastic
limestones only form intercalations. Thus, the upper part is
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UNCORRECTED PROOF
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hic
sect
ion
s(A
,B
,C
,D
,E
,F
,G
,H
)ar
esh
ow
no
nth
em
ap.
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580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
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650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
UNCORRECTED PROOF
Fig
.5
.S
trat
igra
ph
icco
rrel
atio
ns
of
sect
ion
sm
easu
red
inth
eC
arb
on
ifer
ous
of
the
Kar
amb
arU
nit
,to
pp
edb
yth
eG
irch
aF
orm
atio
n(s
eeF
ig.
4fo
rth
eir
loca
tion
).
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694
695
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697
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699
700
701
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703
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705
706
707
708
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718
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720
721
722
723
724
725
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728
729
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731
732
733
734
735
736
737
738
739
740
741
742
743
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745
746
747
748
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764
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767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
UNCORRECTED PROOF
more varied, with marls, marly and hybrid limestones, and
calcareous sandstones.
Fossil content. A single sample (CK1081, collected 35 m
above the base) yielded the following conodonts: Gnatho-
dus pseudosemiglaber Thompson and Fellow, 1970,
Gnathodus typicus morph. 2 Cooper, 1939, and Polygnathus
bischoffi Rhodes, Austin and Ziegler, 1969. In the middle
part of the unit (Triple Junction section), where marls are
more frequently intercalated in the limestone beds, the
brachiopods Sajakella sp. and Ectochoristites sp. were
collected in sample KO14, whereas Anthracospirifer sp. and
Permasyrinxinae gen. indet. were identified from sample
KO15, 30 m higher in the succession. In the upper part of
the unit, in several sections (A,E,F,G,H) and in few
localities (CK 588, Lale Ribat 1) (Fig. 4), the following
brachiopods were collected: Buxtonioides sp., Echino-
conchidae gen. indet., Rhipidomella sp., Martiniopsis
grandiformis (Plodowski, 1968), Spirifer cf. subgrandifor-
mis Plodowski, 1968, S. pentagonoides Plodowski, 1968,
S. cf. denis (Beznosova, 1959), Afghanospirifer sp.,
Choristites sp., Gypospirifer sp., Syringothyris sp., and
Composita sp. Details are given in Section 4.
Age: Late Tournaisian–Bashkirian
Environment. The Ribat Formation represents a fully
marine interval, dominated by high productivity of
carbonates, which were transported towards the basin.
Displaced crinoid ossicles and brachiopod shells are
abundant in places, both in the lower part, representing
the transition from shoreface to open shelf environments,
and in the overlying well-bedded, locally graded beds which
represent the deeper parts of the depositional system.
A gradual increase of clay input is recorded from the middle
part upwards. In the Twin Valleys section 10 s of metre-
thick packages of limestone and marls alternate sharply,
indicating a cyclical clay input in a fairly stable carbonate
depositional system.
3.1.4. The Lupsuk Formation (new name)
We introduce this new unit to identify the thick package
(about 400 m) of fine arenites, siltstones, slates, hybrid
calcarenites and thin conglomerates, which are locally
interposed between the limestones and marls of the under-
lying Ribat Formation and the basal quartzarenites of the
overlying Gircha Formation. This unit has so far been
recognized only in the Karambar Tectonic Unit.
We measured a section along the south side of the Ribat
valley at an altitude of 4550–4650 m, from the snout of the
Zoe Glacier towards the east (Figs. 4–6). The lowermost
part was not measured, cropping out at higher altitude on the
east side of the Zoe Glacier. Possibly the best section is on
the left side of the Lupsuk Glacier from 5150 m upwards.
We only cursorily sampled on the west side of the Lupsuk
Glacier, from 5000 m downwards. Therefore we do not
propose a type section for this unit. North of Karambar
Lake, and particularly in the Lupsuk area, the Lupsuk
Formation is notably richer in carbonates with respect to
the area south of the Karambar Pass.
In the Lupsuk Glacier area the unit begins with coarse,
thick-bedded quartzarenites and microconglomerates, with
cross-lamination and foresets dipping to the N. Upwards,
they pass in hybrid sandstones, still with microconglomera-
tic intercalations. This basal part is about 40 m thick. It is
overlain by grey hybrid arenites and arenaceous limestones,
frequently very rich in crinoid ossicles, in 10–30 cm thick
beds, often amalgamated. The thickness of the horizon
reaches 20 m. The upper part of the succession consists of
grey arenaceous limestones very rich in crinoid ossicles,
with parallel lamination, forming amalgamated packages up
to 10 m thick. The thickness of this interval exceeds 100 m.
The unit ends with approximately 30 m of grey–green
siltstones with sulphate nodules.
On the south side of the Ribat Valley, the section is
dominated by medium to fine arenites in the lower part,
more than 150 m thick. By contrast, siltstones with rare
arenitic intercalations dominate the middle and upper parts
(240 m thick). Rare crinoidal limestone intercalations are
interpersed through the section, in beds exceptionally
reaching 2 m in thickness. In addition, fragments of marine
fossils are present throughout the section.
Fossil content. In the basal part of the unit, Spiriferidae
gen. indet., Afghanospirifer sp., and Gypospirifer sp. have
been collected in the Triple Junction section. Also, the
brachiopods Marginovatia sp., Rhynchopora sp., and
Afghanospirifer sp. characterize the middle part of the unit
along the Ribat section.
At the top of the Twin Valleys section and in the
Lashkargaz gulley (Fig. 4) (Angiolini et al., 1999) a
brachiopod assemblage with Densepustula cf. losarensis
Angiolini and Brunton in Garzanti et al., 1998, Dowhatania
sulcata Angiolini and Brunton in Angiolini et al., 1999,
Septacamera dowhatensis (Diener, 1915), Alispirifer cf.
middlemissi (Diener, 1915), and Brachythyris sp. In the
Lupsuk Glacier area, Dowhatania sulcata also occurs in
arenaceous limestones.
Environment. This unit deserves more extensive and
detailed field analysis. The onset of the formation seems
to be characterized by a renewal of erosion, coarser
terrigenous input to the basin and shore-face to fore delta
environments. Upwards, the northern sector seems to be
proximal to banks or ramps relatively unaffected by
terrigenous input, allowing the flourishing of crinoid
‘meadows’, whose ossicles were swept in by the currents
to form a mixed arenaceous/carbonate ramp. Occasionally,
hummocky structures were observed, also suggesting
the existence of shoals. To the south, however, bottom
energy rapidly decreased and only sporadic arenitic or
biocalcarenitic episodes occurred. The whole succession
seems to consist of marine deposits, judging by their sparse,
but invariably marine, fossils. In the south frequent
bioturbation is preserved. The abundance of phosphates
and glauconies in several levels seems to suggest deepening
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821
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890
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892
893
894
895
896
UNCORRECTED PROOFepisodes with incipient starvation and decrease in terrige-
nous input in a more open shelf environment. This
interpretation also seems to be supported by the reduced
thickness of the unit in the north.
Age: Serpukhovian-latest Carboniferous.
3.1.5. The Twin Valleys Member (new name)
To the east of Karambar Lake, the upper part of the
Lupsuk Formation gives way to a cliff-forming carbonate
unit with sharp lateral variations of thickness, which we
distinguish with the rank of member.
The section in the Twin Valleys was firstly described by
Angiolini et al. (1999, p. 6), who, however, did not
formalize a lithostratigraphic subdivision. The member was
mapped in the Twin Valleys section located just northeast
of the Karambar Lake (3685300000N.–7384503600E.), from
which it derives its name (Figs. 4 and 5).
The Twin Valleys Member comprises 30 to 100 m
of massive bioclastic limestones containing bryozoans,
crinoids, recrystallized brachiopods and corals. This
calcareous unit shows sharp lateral variations in thickness
and is capped by a terrigenous unit, comprising black slates,
sandstones and, more rarely, conglomerates, ascribed to
the Gircha Formation.
Below the Twin Valleys Member, the Lupsuk Formation
consists of 40 m of massive, cross-bedded coarse sand-
stones, bioclastic sandstones and conglomerates, overlain
by 30 m of varicoloured calcareous siltstones with large
Fig. 7. Western side of the Yarkhun valley, near Gharil. The quartzarenitic festooned banks of the Permian Gircha Formation overlie the Visean crinoidal
limestone of the Ribat Formation with a weak angular unconformity.
Fig. 6. The Lupsuk-basal Gircha section along the south side of the Ribat valley. The star show the position of the Asselian fauna (CK 1122).
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1003
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1005
1006
1007
1008
UNCORRECTED PROOF
crinoids and fine arenites with intercalations of marly
limestones containing bryozoans, corals and brachiopods.
Environment. The Twin Valleys Member represents a
local enrichment of bioclastic sands, accumulated under
tractive load-carrying current conditions. Continuing
upwards the tendency towards higher bioclastic content
and higher energy, already observed in the Ribat and
Lupsuk Formations in the northern part of the Karambar
thrust sheet, is also seen here.
Age: ?Late Carboniferous, lying above a Moscovian or
Kasimovian brachiopod fauna (Angiolini et al., 1999).
3.1.6. The Gircha Formation (Desio, 1963)
The Gircha Formation is widespread throughout the
Northern Karakoram. In the Karambar area three major
lithozones can be identified. From the base upwards they are:
(A) Alternations of well-bedded grey fine arenites
(arkoses) and dark siltstones, occasionally lighter and
contain thicker arenitic packages, up to 6 m thick. Most
important was the finding on the south side of the Ribat
valley, at 4550 m (Fig. 6), of a 2 m-thick siltstone level,
packed with brachiopods (new species of Bandoproductus,
Kiangsiella sp.; two species of Trigonotreta, Spirelytha
petaliformis (Pavlova, 1973), Punctospirifer afghanus
Termier, Termier, de Lapparent and Marin, 1974 and
large dielasmatids) of Asselian age. Thickness 165 m.
(B) Monotonous grey siltstones and dark grey splintery slates
with rare m-thick arenitic intercalations. The slates are
occasionally bioturbated. The thickness exceeds 360 m. The
western tongue of the Karambar Glacier flowing towards the
Karambar Pass covers the remaining part of the section (Fig. 4).
(C) In the core of the syncline between the western
branches of the Karambar Glacier, a unit of thick-bedded
and lighter arenitic beds crop out, over 100 m thick. They
also crop out on the Pakistan–Afghanistan border to the
N of the small lakes west of the Karambar Pass. Some
of them are fine-grained, moderately to well-sorted
subarkose, containing rare granitoid to hypabyssal-as
well as volcanic-rock fragments, and some intrabasinal
pseudomatrix (Dickinson, 1970).
At the present stage of knowledge, the lower boundary of
the Gircha Formation is rather easily defined in the field
where the base of the Gircha is rich in sandstone layers. In
the Karambar area the position of the boundary, where the
basal part consists of alternating arenites and siltstones,
remains uncertain. The change from hybrid quartzarenites,
commonly barren in lithics, to lithic-bearing arkoses,
subarkoses and quartzarenites, with sharply decreasing
intrabasinal grains, is the most reliable distinctive criterion.
3.2. The Lashkargaz/Baroghil Unit
In this tectonic unit, the Carboniferous succession is
represented only by the lower two formations (Fig. 7).
The Margach Formation outcrops on the ridge between
Baroghil Pass and the Vidiakot gulley (Figs. 3 and 8). There
Fig. 8. Geological map of the Baroghil area, from Zanchi et al. (2001). Location of the map in Fig. 3. The measured stratigraphic section is shown on the map, in
the northwest corner.
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1025
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1028
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1038
1039
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1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
UNCORRECTED PROOF
it is represented by about 100 m of highly cleaved blackish
slates and siltstones. In this section other Carboniferous units
are absent; the Gircha Formation rests with a faulted contact
on the Margach Formation. Elsewhere this unit is absent or
poorly exposed due to tectonics and a subdued topography.
Along the Yarkhun Valley around Gharil (Fig. 7, the
Margach Formation is tectonically reduced and the base
of the Ribat Formation consists of dark laminated marls.
These gradually become more calcareous upwards, with
10–30 cm thick layers of dark grey limestones rich in
crinoid ossicles, reaching a maximum thickness of about
50 m. They are directly overlain by the Gircha Formation,
with a low-angle unconformity. This locality has been
already quoted in Gaetani et al. (1996). Most important is
the finding, about 10 m below the top of the Ribat
Formation along the northern river bank, of conodonts
(sample CK1125). Gnathodus semiglaber Bischoff, 1957,
G. delicatus Branson and Mehl, 1938, G. cuneiformis
Mehl and Thompson, 1947, G. typicus Cooper, 1939;
and Siphonodella lobata Branson and Mehl, 1934
were identified. The specimen of G. cuneiformis is a
young form such as that illustrated by Lane et al. (1980,
pl. 10, fig. 7).
3.3. The Lasht Unit
Carboniferous rocks in the Lasht Unit (Fig. 3) are present,
but because of tectonics they can rarely be measured along
complete sections and identifiable fossils cannot be col-
lected. A section near Rukut (near Lasht), mostly made of the
crinoidal limestones of the Ribat Formation, has already been
illustrated briefly in Gaetani et al. (1996, fig. 12). Another
outcrop, some 50 m thick, with Carboniferous brachiopods
was found along the trail to Siru An (Fig. 9). Here, on
the eastern flank of the floodplain (4100 m) where the Siru
Creek is dammed by the lateral moraine of the Siru Glacier,
dark grey marly limestones in 40–70 cm-thick layers
crop out, with sparse crinoids and few productids
and rhynchonellids (CK1139). Brachiopods (Cubacula sp.
ind., a Dictyoclostinae gen. indet., and a Tolmatchoffini gen.
ind.) identified in this unique calcareous horizon within a
mostly terrigenous succession indicate a Kasimovian age
(Late Carboniferous).
3.4. Buattar
Black marly limestones and bioclastic limestones in the
tectonic slices on the hanging wall of the Upper Hunza fault,
contain few Rhipidomella sp. (Angiolini et al., 1999, p.7).
3.5. The Chillinji Unit
To the south of the Reshun-Upper Hunza Fault (Fig. 2),
possible Carboniferous rocks have been identified only in the
Chillinji Unit. In other areas, the calcareous layers seem to be
absent and we were not able to confirm a Carboniferous age
in this anchimetamorphic terrigenous succession. To the
south of Shost and Lashkargaz, the oldest carbonate rocks are
apparently Permian (Gaetani et al., 1996).
The top of the Baroghil Group (Quintavalle et al., 2000),
overlain by the dolostones of the Chilmarabad Formation,
crops out in the core of the Chillinji anticline (Fig. 10). Then
follow hybrid sandstones and heavily recrystallized coral-
tabulate bafflestones, attributed to the Shogram Formation.
Above this coral horizon, about 80 m offine-grained arenites,
hybrid arenites, siltstones and dark slates follow. Near the
base of this terrigenous unit poorly preserved Schuchertellid
Fig. 9. Lasht Unit. The star indicates the location of the dark marly limestones with brachiopods in the Siru Gol.
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ARTICLE IN PRESS
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1122
1123
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1126
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1138
1139
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1141
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1177
1178
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1180
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1183
1184
1185
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1187
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1189
1190
1191
1192
1193
1194
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1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
UNCORRECTED PROOF
brachiopods were collected and tentatively ascribed to the
Carboniferous (Angiolini et al., 1999).
4. Biostratigraphy
Besides two productive conodont samples, the biostrati-
graphy was based on brachiopods. The brachiopod assem-
blages of the Margach, Ribat and Lupsuk Formations have
been analysed by means of the Unitary Associations method
of Guex (1991), to which the reader is referred for a
comprehensive explanation. Different runs have been
processed with the BioGraph Program and BioGraph Tools
(Savary and Guex, 1991; Savary and Guex, 1999), giving
conflicting results. The data-set was modified by adding or
removing localities and eliminating suspect occurrences or
taxa with very low geofrequency until an optimal result with
minimum contradictions was reached.
A first run based on 28 taxa distributed in 7 sections
(Fig. 5) and 5 localities (Lashkargaz, Lale Ribat, and 3
localities (CK588-590-591, Fig. 4) near the Karambar
Pass, yielded 4 Unitary Associations (UAs) with good
superpositional control but rather low lateral reproducibility
(Fig. 11 for details). A second run was then performed
removing the taxa higher than generic level and the species
with very low geofrequency, which only occur in single
samples (such as Rugosochonetes sp. ind., Sajakella sp.
ind., Buxtonioides sp. ind., Marginovatia sp. ind.,
Fig. 10. Geological map of the Chillinji area, from Zanchi et al. (2001). Location of the map in Fig. 3. The stratigraphic section was measured on the northern
bank of the Karambar River.
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1234
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1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
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1263
1264
1265
1266
1267
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1269
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1271
1272
1273
1274
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1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
UNCORRECTED PROOF
Marginoproductus ribatensis n. sp., Ectochoristites sp. ind.,
Spirifer cf. denis, S. subgrandiformis, Syringothyris sp. ind.,
and Composita sp. ind.). However, species occurring at
several levels, but in a single section were retained, even if
they have a low geofrequency in the sense of Guex (1991, p.
103). This run, processing a data set of 14 taxa distributed in 6
sections (the Karambar Pass section having been removed)
and 5 localities, yelds 3 UAs (see Fig. 12 for details).
These results, however, do not solve the problems of the
numerous indeterminate relationships between the taxa and
of the correlations of the lower part of the Carboniferous
succession, where only 1 UA has been identified. To
address this issue, we added biostratigraphical data taken
from the Carboniferous succession of Central Afghanistan
(Plodowski, 1968, 1970). These data have been summarized
in a composite section derived from the range charts
published by Plodowski (1970, tab. 1, 2, p. 125–132), taking
into consideration only the genera and species shared with
the Karakoram succession. An optimal result was thus
achieved processing 21 taxa distributed in 8 sections and 5
localities (i.e. the 7 sections and 5 localities from Karakoram
plus the composite section from Central Afghanistan), which
yields five UAs (Fig. 13). The correlation table obtained
by this data-set (Fig. 14) clearly displays the correlation
among the fossiliferous level of the E. Lupsuk section
and the Lale Ribat 1, Karambar CK588, and Karambar
CK590 localities. Only the Karambar Pass section is thus left
undetermined.
Fig. 11. Results of the first run (all the sections of Figs. 4 and 5 localities) showing the composition of the Unitary Associations, the reproducibility matrix, the
reproducibility graph with the superposition of the UAs and the number of contradictions between the maximal cliques. This run yields 4 UAs with good
superpositional control. The number of contradictions between the maximal cliques is 52, but this results from pure indetermination as no forbidden generated
subgraphs occur. The lateral reproducibility of UAs 1 and 2 is very low, the UAs being strictly identified only in the Triple Junction section. Furthermore, UA 1
and UA 2 contain species with unclear relationships and very low geofrequency, as a result of insufficient sampling. UA 1 is characterised by the pair of species
Ectochoristites sp. ind.-Sajakella sp. ind. and UA 2 by the pair Anthracospirifer sp. ind.- Permasyrinxinae gen. indet., which only occur in single samples at the
Triple Junction section. UA 3 and UA 4 are both well defined and have a high reproducibility coefficients of 5 and 4 respectively. UA 3 is characterised by the
pair of taxa Afghanospirifer cf. burgutschensis and Gypospirifer sp. ind. and has been detected in four sections and one locality (CK 591, Karambar Lake). UA
4 records the main change in composition, with the first occurrence of Dowhatania sp. ind., Densepustula cf. losarensis, Septacamera dowhatensis and
Alispirifer cf. middlemissi. However, this UA includes also the assemblage KO25 (Syringothyris sp. ind., Buxtonioides sp. ind. and Echinochonchidae gen.
indet.) which has been found only in the Karambar Pass section and that is completely different from the other assemblage. Its inclusion in UA 4 is probably an
artifact due to the very restricted occurrence of the KO25 assemblage (very low geofrequency).
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UNCORRECTED PROOF
Based on the quantitative biostratigraphic analysis of the
brachiopod assemblages, four biozones have been detected,
all separated by barren intervals:
1. The Parallelora aff. subsuavis-Rhipidomella sp.1 Bio-
zone: correponds to UA’ 1 and comprise the index
species and a species of Rhynchopora, which however
ranges up to the third biozone. This biozone occurs only
in the Ribat section, apart from the composite section
from Central Afghanistan.
2. The Spirifer pentagonoides-Martiniopsis grandiformis
Biozone: corresponds to UA’ 2 and 3 in the Ribat
Formation in the East Lupsuk section and at the Lale
Ribat 1, Karambar CK588, and Karambar CK590
localities. It is also recognizable in Central Afghanistan.
In addition to the index species, it includes Margin-
oproductus ribatensis n. sp., Spirifer cf. denis, S.
subgrandiformis, Syringothyris sp. ind., and Composita
sp. ind. and the two species of Rhipidomella.
3. The Afghanospirifer cf. burgutschensis-Gypospirifer sp. ind.
Biozone: also include Rugosochonetes sp. ind., Marginovatia
sp. ind., Choristites sp. ind., Rhipidomella sp. ind. 2,
Syringothyris sp. ind. and Composita sp. ind. This biozone
extends laterally in 4 sections out of 8 in the Karakoram and in
the composite section for Central Afghanistan. The biozone
corresponds to UA’ 4 and mostly characterizes the upper part
of the Ribat Formation, but it also occurs in the Lupsuk
Formation (Ribat section), indicating that it is not ecologically
controlled.
4. The Densepustula cf. losarensis-Septacamera dowhatensis
Biozone: also includes Dowhatania sulcata, Brachythyris sp.
ind., and Alispirifer cf. middlemissi. This biozone (UA’ 5)
occurs in two sections, in the Lupsuk Formation and in its
Twin Valleys Member, and at the Lashkargaz locality.
The correlation of these biozones is shown on the
sections in Fig. 5, which are also independently correlated
by means of lithological markers.
It is important to notice that the biozones and the major
faunal changes (Fig. 15) do not strictly correspond to
lithological changes and are probably not ecologically
controlled. For instance, the Afghanospirifer cf. bur-
gutschensis-Gypospirifer sp. ind. Biozone occurs both at
the top of the Ribat Formation and in the Lupsuk Formation,
Fig. 12. Results of the second run (14 taxa distributed in all the sections of Fig. 4, except for the Karambar Pass section, and 5 localities) showing the
composition of the Unitary Associations, the reproducibility matrix, the reproducibility graph with the superposition of the UAs and the number of
contradictions between the maximal cliques. This run yields 3 UA with good superpositional control and only 8 contradictions resulting from pure
indetermination, as no forbidden generated subgraphs have been detected. The reproducibility of UA 1 is again low, but it is a result of insufficient sampling,
whereas that of UA 3 ðR ¼ 3Þ and especially UA 2 ðR ¼ 5Þ is good. UA 1 is characterised by the pair of species Parallelora aff. subsuavis-Rhipidomella sp.
ind.; UA 2 by Afghanospirifer cf. burgutschensis-Gypospirifer sp. ind. (as UA 3 of the first run) and UA 3 by the pair Densepustula cf. losarensis-Septacamera
dowhatensis (as UA 4 in the first run).
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UNCORRECTED PROOF
and it crosses the boundary between the two formations in the
Triple Junction section (Fig. 5).
5. Chronostratigraphy
We have no age constraints on the lower part of the
Margach Formation, which could be uppermost Devonian:
Receptaculites (CK1066) is a wide-ranging genus
(Hubmann, pers. comm., 2003), and no fossils have
been discovered in the second lithozone. Instead, the
third lithozone is characterized by the Parallelora aff.
subsuavis-Rhipidomella sp. 1 Biozone, which, according to
the distribution of the genera Parallelora and Rhynchopora,
should span the earliest middle Tournaisian. In fact, the
genus Parallelora is late Fammenian–early Tournaisian
and it is followed by a stratigraphic interval devoid of
similar spiriferids before the first appearance of the genus
Spirifer in the middle Tournaisian (Carter, 1992). The
species subsuavis has been reported from Etroeungtian
crinoidal limestones and sandstones of Chuschk-Kol-Tal
(Bukhara-e-Nawar, Central Afghanistan) by Plodowski
(1970). More specifically, the associated Central Afghani-
stan conodonts Polygnathus inornatus, P. symmetricus,
Fig. 13. Results of the last run (21 taxa distributed in all the sections of Figs. 4 and 5 localities and the Central Afghanistan composite section.) showing the
composition of the Unitary Associations, the reproducibility matrix, the reproducibility graph with the superposition of the UAs and the number of
contradictions between the maximal cliques. The number of forbidden generated subgraphs and the list of Z’4 circuits—each with one superpositional
relationship known—are also shown. This run yelds five UAs (here named UA’), with good superpositional control and significant lateral reproducibility,
except for UA’ 3, which could be merged with UA’ 2 as their inter-UA distance is the lowest (0.83; calculated according to Guex, 1991, p. 166–167). The
number of contradictions between the maximal cliques is 8, but they can be solved by adding virtual co-existences, as no forbidden configurations of length 3
and 4 occur, except for 6 circuits of length 4 (Z’4). For instance, the chronological sequence of A. cf. burgutschensis above M. grandiformis and S.
pentagonoides implies that Syringothyris sp. ind. and Rhipidomella sp. 2 should virtually co-exist.
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UNCORRECTED PROOF
Bispathodus spinulicostatus, B. stabilis-listed in Plodowski
(1970, p. 12–13)-indicate the mid-Tournaisian Early
crenulata Zone, according to the range charts of Mawson
and Talent (1999).
The overlying Ribat Formation is well constrained
between the late Tournaisian and the Bashkirian, although
its top is diachronous and does not always reach the
Bashkirian (i.e. in the E. Lupsuk section).
The age of the base of the Ribat Formation is constrained
by the conodont association collected in the Ribat section
(CK1088: Gnathodus pseudosemiglaber Thompson and
Fellow, 1970, Gnathodus typicus morph. 2 Cooper, 1939,
and Polygnathus bischoffi Rhodes, Austin and Ziegler,
1969). Using the ranges given by Lane et al. (1980, p. 121),
the age of this fauna must be the upper half of the
anchoralis-latus Zone as G. pseudosemiglaber makes its
first appearance at the middle of the anchoralis-latus Zone
and Gnathodus typicus morph. 2 disappears at the
anchoralis-latus Zone/texanus Zone boundary. Therefore
the age is Late Tournaisian.
Another conodont sample (CK1125), from the Lashkar-
gaz-Baroghil Unit, contains a conodont assemblage domi-
nated by Gnathodus species. According to the range chart of
Lane et al. (1980), the age of this fauna is from just above
the base of the typicus Zone to the mid anchoralis-latus
Zone, as G. cuneiformis does not appear until just above the
base of the typicus Zone and the highest occurrence of G.
delicatus is mid-anchoralis-latus Zone. Therefore this
sample is also Late Tournaisian in age, but slightly younger
than the previous conodont sample.
In the middle part of the unit (sample KO14–KO15,
Triple Junction section) where marls are more frequently
intercalated in the limestone beds, the brachiopods
Sajakella sp. ind., Anthracospirifer sp. ind., and Ectochor-
istites were collected. They were not considered in the
biostratigraphic analysis above, because of their very low
geofrequency; however, they suggest a probable Serpu-
khovian age for these beds, according to the combined
occurrence of the three genera (the former two spanning
the Serpukhovian–Bashkirian time interval and the latter
the Tournaisian-?‘Namurian’).
In the upper part of the unit, in several measured sections
and isolated localities, the brachiopods of the Afghanospir-
ifer cf. burgutschensis-Gypospirifer sp. ind. Biozone
indicate a Bashkirian age. In fact, the genus Afghanospirifer
occurs in the late Serpukhovian–early Bashkirian of Central
Afghanistan (SW Dasht-e-Nawar); Marginovatia ranges
from the middle Visean to the Bashkirian. The same age
assignment was already suggested by Angiolini et al. (1999).
Other age constraints for the Ribat Formation come
from the E. Lupsuk section, where the Spirifer pentago-
noides-Martiniopsis grandiformis Biozone was sampled
near the top of the formation, indicating a Visean age
according to the distribution of the spiriferid species, which
in Central Afghanistan are associated with Gnathodus
texanus Roundy (Plodowski, 1970). This is confirmed by
the concurrence of the genus Marginoproductus, known
from the Visean of South China. On the other hand, in the
Karambar Pass section (Fig. 5), a low geofrequency
brachiopod assemblage has been collected in the upper-
most part of the formation. This suggests a Bashkirian
Fig. 14. Correlation table of the section and localities processed in the last run (Fig. 13). The numbers refer to the UA’s. Worthy of note is that the fossiliferous
level of the E Lupsuk section can be attributed to the new UA’ 2 (merged with UA’ 3) and correlated to the Lale Ribat 1, Karambar CK588, and Karambar
CK590 localities, whereas only the Karambar Pass section is left undetermined. The relationships of these UA’s with those obtained in the previous run and
displayed in Fig. 12 are as follows: the newly obtained UA’ 1 corresponds to the previous UA1, UA’ 4 corresponds to UA 2 and UA’ 5 corresponds to UA 3,
whereas the newly detected UA’ 2 þ UA’ 3 is an intermediate unitary association between the former UA 1 and UA 2.
Fig. 15. Graphs showing the species diversity and the rates of faunal
turnover calculated from the results of Fig. 13. There is a nearly constant
diversification from UA 1 to UA 3, followed by a reverse trend to UA 4 and
then by a constant rate between diversification and extinctions to UA 5,
which has the maximum inter-UA distance to UA 4 ðd ¼ 2Þ:
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UNCORRECTED PROOF
age based on the co-occurrence of the genera Buxtonioides
and Syringothyris, the latter similar to Syringothyris
sp. 2 described by Plodowski (1970) from the late
Serpukhovian-early Bashkirian of Burgutsch-Tal (13 km
SW Bukhara-e-Nawar, Central Afghanistan).
The Lupsuk Formation in part interfingers with the Ribat
Formation (Fig. 5) and its diachronous base ranges from the
Serpukhovian to the Upper Carboniferous. This formation is
characterized, at its base in the Triple Junction section and
in its lower part in the Ribat section, by the Afghanospirifer
cf. burgutschensis-Gypospirifer sp. ind. Biozone,
suggesting a Bashkirian age for its lower part. However,
its base is probably older (Serpukhovian) in the Ribat and
E. Lupsuk sections.
In the middle part of the unit in the west Lupsuk
section and at its top in the Twin Valleys section-below
the Twin Valleys Member-, the Densepustula cf.
losarensis-Septacamera dowhatensis Biozone indicates a
Moscovian-Kasimovian age (Angiolini et al., 1999).
The age of the Twin Valleys Member is poorly
constrained, but it overlies the Densepustula cf. losaren-
sis-Septacamera dowhatensis Biozone and extends up to the
terrigenous Gircha Formation. This unit should therefore be
of Late Carboniferous age.
The Carboniferous succession is covered by the shales
and quartzose sandstones of the Gircha Formation, includ-
ing a characteristic brachiopod assemblage about 133 m
from its base (Figs. 5 and 6), with Bandoproductus sp.,
Kiangsiella sp., two species of Trigonotreta, Spirelytha
petaliformis (Pavlova, 1973), Punctospirifer afghanus
Termier, Termier, de Lapparent and Marin, 1974 and
large dielasmatids indicating an Asselian age.
6. Sandstone petrography
6.1. Materials and methods
Bulk petrography of sandstones from the Karambar and
Baroghil/Lashkargaz units was analyzed quantitatively
through point-counting of 300 points on standard
25 £ 40 mm thin sections, previously stained with red
alizarine. Detrital modes were recalculated following the
Gazzi–Dickinson method: standard descriptive parametres
are those of Dickinson (1970) ðQ; F; L; C=Q; P=F; V=LÞ and
Zuffa (1980) (NCE, CE, NCI, CI). QFL modes allow
interpretation of sand provenance (Dickinson, 1985),
whereas parametres by Zuffa (1980) are specific for
classifying hybrid arenites and allow correct interpretation
of carbonate and/or intrabasinal grains. Sandstone nomen-
clature relies instead on the widely understood QFR modes
(Folk, 1974).
Grain size and sorting of all samples were semiquantita-
tively evaluated in thin section following the method
described in detail in Sciunnach (1996). A total of 29
samples was analysed, and the results are briefly summarised
in this section (Fig. 16). Unfortunately, most of the sandstone
samples from the Margach type-section were lost in the mail.
6.2. The Margach Formation
Lithozone B ðn ¼ 2Þ: Moderately to well-sorted, fine-
grained subarkoses very rich in detrital mica. Mostly
untwinned plagioclase prevails over K-feldspar ðP=F ¼
0:9Þ; and rock fragments are negligible. White mica and
‘leached’ biotite flakes make up to 5% of rock volume, but
also rutile, opaques, zircon and tourmaline are abundant.
Intrabasinal grains are limited to scarce muddy pseudoma-
trix (Dickinson, 1970).
Lithozone C ðn ¼ 2Þ: Moderately to poorly-sorted, fine to
medium-grained pure quartzarenites and hybrid encrinites.
Quartz is mostly monocrystalline, and only rare plagioclase,
volcanic rock fragments and undetermined ‘dirty’ lithics are
observed. Heavy minerals are limited to the ultrastable
zircon–tourmaline–rutile (ZTR) assemblage and some
opaques. Among bioclasts, echinoderm plates prevail over
brachiopod valves, bryozoans and ostracods.
6.3. The Ribat Formation
Moderately to well-sorted, medium-grained hybrid
quartzarenites and sandy encrinites are found only at the
very base of this limestone-dominated formation ðn ¼ 2Þ:
Polycrystalline quartz slightly increases ðC=Q ¼ 0:030Þ
with respect to the underlying Margach Formation
ðC=Q ¼ 0:015Þ; possibly also as an effect of increased
grain size. A few plagioclase grains, both twinned and
untwinned, were counted; K-feldspar is absent, and rock
fragments are negligible. Oversized phosphate grains
(sandy, bioclastic and pure collophanites following the
classification of Assereto, 1969) are widespread: among
bioclasts, echinoderm plates prevail over brachiopod valves
and spines, as well as minor bryozoan colonies.
6.4. The Lupsuk Formation
Mostly well-sorted subarkoses to feldspathic quartzar-
enites, locally containing plenty of glauconitic pellets and
pseudomatrix (‘subarkosic petrofacies’), alternate with
moderately to very poorly-sorted hybrid quartzarenites,
commonly bioclastic, but also containing traces of phos-
phate (‘hybrid petrofacies’).
Subarkosic petrofacies ðn ¼ 8Þ:Grain size of the analysed
samples ranges from fine to medium. Among feldspars,
twinned plagioclase, chessboard albite and microcline are
abundant at definite stratigraphic intervals; hypabyssal,
volcanic and undetermined rock fragments are also common.
The heavy mineral suites are dominated by the ZTR
assemblage, with minor apatite and opaques. Intrabasinal
grains are limited to a glauconitic interval in the Lupsuk
section, where silicified bryozoans and brachiopod valves,
their endopunctae filled with glaucony, also occur; negligible
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UNCORRECTED PROOF
muddy pseudomatrix and echinoid plates are recorded in the
Ribat section.
Hybrid petrofacies ðn ¼ 7Þ: Grain size of the analysed
samples ranges from very fine to very coarse. Embayed
quartz occurs only concurrent with the maximum
abundance of volcanic lithics, hinting at a volcanic episode
that is documented also by interlayered tuffs; polycrystalline
quartz notably increases with respect to the underlying
units, the C=Q ratio averaging 0.1. Rare feldspar (mostly
untwinned plagioclase and chessboard albite) and granitoid
to volcanic grains occur. Heavy minerals include the ZTR
assemblage, as well as some white mica and sphene. Both
carbonate and non-carbonate intrabasinal grains are
abundant: CI grains document rich faunal assemblages
including echinoderms, brachiopods, pelecypods, gastro-
pods, bryozoans and foraminifers, whereas NCI grains
include phosphate (silty to sandy collophanites after
Assereto, 1969), silty to pure ferricrete chips, oversized
chert (silcrete?) and mudclasts.
6.5. The Gircha Formation
Mostly moderately to well-sorted arkoses, subarkoses
and quartzarenites; grain size of the analysed samples
ðn ¼ 8Þ ranges from very fine ðF ¼ 3:50Þ to coarse
ðF ¼ 0:50Þ: Embayed quartz is abundant only in one
interval, about 40 m above the formational base at Ribat,
where abundant non-carbonate, intrabasinal matrix and
sparse terrigenous to metamorphic lithics are also recorded.
This peculiar interval is thus best ascribed to a ravinement
surface (possibly an Incised Valley Fill?), and quartz
embayments to chemical leaching in soils, rather than to
an episode of volcanic activity. Both twinned and
untwinned plagioclase, K-feldspar and chessboard albite
are common, as are the hypabyssal lithics: granitoid rock
fragments are locally abundant even in medium-grained
sandstones. Volcanic and undetermined ‘dirty’ rock frag-
ments are common, although they account for at maximum
1% of rock volume. Heavy minerals are mostly limited to
the ZTR assemblage; a few apatite and white mica grains
occur in only one sample. Intrabasinal grains are rare and
mostly consist of oversized chert (silcrete?) and muddy
pseudomatrix: only in the Twin Valleys section abundant
bioclasts include echinoderm plates, brachiopod and
pelecypod valves, bryozoan colonies and foraminifer tests.
6.6. Sand provenance and compositional trends
In the studied sample population, correlation of detrital
modes with textural parametres is generally poor; coarser
Fig. 16. QtFL (Dickinson, 1985) and NCE-NCI-CI (Zuffa, 1980) triangular plots for the 29 analysed arenite samples. Textural data (grain size, sorting) are
available upon request.
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UNCORRECTED PROOF
sandstones tend to be more quartzose and finer sandstones
tend to be more feldspathic (Odom et al., 1976), but this
accounts for only 40% of the variations of individual Q; F
parametres and only for one third of their concurrent
variation. Also higher C=Q in coarser sandstones and worse
sorting in CI-rich arenites are obvious characters; however,
the corresponding correlation coefficients are rather low
(around 0.8). Thus, it can be stated that composition of
the analysed Upper Devonian? to Lower Permian sand-
stones provides useful hints for unravelling the tectonic and
magmatic evolution of the Karakoram, because most
petrographic signals have to be interpreted as provenance
signals.
Fine-grained subarkoses, notably enriched in detrital
mica flakes, of the Margach Formation—Lithozone B
(Upper Devonian?) suggest provenance of prevailing first-
cycle detritus from uplifted metamorphic rocks.
The overlying Carboniferous succession (Lithozone C of
the Margach Formation, Ribat and Lupsuk Formations) is
dominated by up to coarse-grained, hybrid quartzarenites
interlayered with shelf limestones and marls. Intrabasinal
grains, both carbonate (bioclasts) and non-carbonate
(phosphorite, glaucony, silcrete, ferricrete), are highly
variable in abundance depending on the depositional setting,
so that subarkoses to pure orthoquartzites alternate with
sandy encrinites. A major sequence boundary corresponds
to a ravine-eroded surface at the top of the Margach
Formation: the only arenite samples from the Ribat
Formation were obtained at its very base, from shelf margin
system tract deposits (just 15 m thick) sharply overlain by
transgressive crinoidal limestones.
In the Lupsuk Formation the hybrid quartzarenite facies
alternates with subarkoses, strongly condensed at Lupsuk,
where they contain abundant glauconite and are considered
as largely Bashkirian in age. At Ribat the subarkoses seem
to span a longer period, Bashkirian to Moscovian, and
contain chessboard albite, volcanic rock fragments and
microcline pointing to a stage of active volcanism coupled
with unroofing of granitoid basement rocks. As a whole,
feeble petrographic signals preserved in both the hybrid
quartzarenites and the interlayered subarkoses actually point
to a major rifting stage, during which portions of the former
passive margin experienced differential drowning and local
sediment starvation. Ongoing syn-rift volcanism and
unroofing of basement rocks exposed on the uplifted rift
shoulder are suggested by small amounts of unstable grains,
but volcanism is also documented by interbedded micro-
lithic spilites.
In all sections, the syn-rift succession is capped by fossil-
poor arkoses to quartzarenites (‘typical’ petrofacies of the
Gircha Formation as described in Gaetani et al., 1995).
Slightly, but steadily increased abundance of K-feldspar and
lithic grains in these sandstones hint at continued unroofing
of a mature rift shoulder, basin inversion and local erosion
of the syn-rift succession.
7. Geodynamic evolution during the Carboniferous:
discussion and conclusions
It is probably too ambitious at this reconnaissance stage of
our field work to construct the geohistory of the Northern
Karakoram. Although a palinspastic restoration of the
analysed thrust sheets has not yet been performed, some
general remarks drawn from our data are noteworthy. The
present curvature of the western part of Karakoram may be
quite recent (Hildebrand et al., 2000), and can be partially
related to NE–SW oriented left-lateral strike-slip faults,
displacing an originally E–W trending belt. These fault
systems are evident along the Yarkhun Valley from Khan
Khun to Lasht. The Lasht Unit shows S-vergent structures as
the Baroghil-Lashkargaz Unit. The Karambar Unit has a
complex structural pattern suggesting westward motion
above the Baroghil-Lashkargaz Unit, and minor northward
motion in its eastern part. The Chillinji Unit and the tectonic
slices along the Upper Hunza Fault show an important
northward translation. This suggests that the Lasht, Baroghil-
Lashkargaz and Karambar Units were probably originally
lying along a transect, oriented approximately E–W in
origin. The Chillinji area was in a more southern position. To
the north of these units, in present geographical coordinates,
additional unknown domains should be present on the
Whakan side. Finally, the Tash Kupruk Unit should have
been located further north. We assume also that the
metasediments of the Axial Unit (Gaetani et al., 1996)
were lying to the south of the previous units. The supposed
development of the Carboniferous rocks along this belt is
summarized in Fig. 17.
It appears that the succession increases in thickness and it
is most complete from south to north in present coordinates.
Apparently no Carboniferous rocks are preserved in the
Axial Zone and the Permian arenites of the Gircha lie
directly above the slates of the Lower Palaeozoic Baroghil
Group (Gaetani et al., 1996). In the Chillinji Zone, about
215 m of dolostones, hybrid arenites and coral bafflestones
(Chilmarabad and Shogram Formations-Devonian) are
interposed between the slates of the Baroghil Group and
the terrigenous succession, which possibly contains also
some Carboniferous sandstones and siltstones. In the Lasht
(besides the single outcrop along the SiruGol
with Upper Carboniferous brachiopods, Fig. 9) and
Baroghil-Lashkargaz thrust sheets only the lowermost part
of the Carboniferous succession is preserved and is
unconformably overlain by the Gircha Formation. The
succession younger than late Tournaisian, if it was ever
deposited, was later eroded. Only in the Karambar thrust
sheet does the succession exceed 1000 m in thickness and
contain also Upper Carboniferous rocks.
We interpret this transect as a part of the continental
margin of the Karakoram Terrane, facing a deeper basin
mostly filled by the Wakhan/Misgar Slates.
The first step in the evolution of the margin could
possibly be traced back to the Devonian, when the peritidal
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UNCORRECTED PROOFplatform of the Chimarabad Formation emerged and was
covered by the conglomerates at the base of the Shogram
Formation. Precise timing has not yet been firmly defined
(mid-Givetian?). The Shogram Formation may reach 180 to
250 m in thickness, with a sedimentation rate (not decom-
pacted) of 11 to 15 m/My. Upwards, terrigenous input
becomes abundant, but is usually fine grained, with intervals
of coarser arenite. Particularly the lithozone B of the
Margach Formation (Late Devonian?), deposited in open
shelf conditions on the passive continental margin, but
seemingly accompanied by block-faulting and relative
tectonic uplift of metamorphic rocks in the source area,
can be related to the onset of rifting, with a sedimentation
rate which may reach 30 m/My. The widespread occurrence
of the transgressive shelf limestones and marls, particularly
rich in crinoidal ossicles, seals this initial rifting event.
The foreset/topset couples observed at the base of the
Ribat Formation point to a northwards aggradation of the
shelf. Also to be noted is the more terrigenous character of
the southern Karambar sections, in comparison to the more
carbonate rich succession to the north. However, these latter
are richer in non-carbonate intrabasinal grains, suggesting
that the terrigenous input reduced northwards and the shelf
was open to deeper water influx and sedimentary
starvation. Instead, subarkoses to pure orthoquartzites
were intermittently laid on the shelf. The sedimentation
rate decreases to around 10 m/My.
The reduced thickness of the Lupsuk Formation around
the Lupsuk glacier, where arenites contain abundant
glauconite, indicates that the previous paleogeographic
position (edge of the shelf?) was still persistent in
Serpukhovian/Bashkirian to Moscovian/Kasimovian times.
To the south, the arenites document active volcanism, also
recorded by interbedded microlithic spilites, coupled with
unroofing of granitoid basement rocks. In addition to the
petrographic evidence, the erosion and gentle tilting of the
Carboniferous succession in the Baroghil-Lashkargaz Unit
and the general trend along the transect, actually point to
a major rifting stage, where rift shoulders were uplifted and
eroded and the unroofing of basement rocks was continuing.
The sedimentation rate slightly increases to 15 m/My.
The generally widespread occurrence of the Gircha
Formation, even if its onset was gradual, seems to
definitively seal the previous syn-rift succession. Therefore,
we propose to draw the break-up unconformity within the
lower part of the Gircha Formation (?latest Carboniferous-
Asselian in age). (Figs. 17 and 18).
Only much more field work will allow a more accurate
interpretation of the rift succession. The major inconsis-
tency in interpreting the Carboniferous succession in term of
rift sequence is the apparently low sedimentation rate, an
unusual character in a rift sequence. We do not exclude the
presence of as yet unidentified gaps.
The data and interpretations of Zanchi et al. (2000) and
of the present paper refine the general geodynamic picture
of Gaetani (1997). The evidence of mantle peridotites
emplaced between the Karakoram and East Hindu Kush and
deformed in pre-Cretaceous times strengthens the general
Fig. 17. Stratigraphic scheme along the transect from the Karambar unit to the Axial metasediments. To be noted the unusual occurrence of Kasimovian
sediments in the Lasht Unit at Siru Gol locality (Fig. 9).
Fig. 18. Cartoon of the geometric relationships below the break-up
unconformity sealed by the Gircha Formation.
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UNCORRECTED PROOF
picture of a block fragmentation along the Northern
Gondwanan margin, with thinned crust and hypothetical
short living oceans between blocks (Leven, 1995).
The geodynamic evolution observed in the North
Karakoram Terrane adds evidence that extensional
movements, starting from the Middle/Late Devonian,
widely involved the Perigondwana fringe from south
East Asia (Metcalfe, 1996 and refs. therein), the Central
Himalaya (Garzanti, 1999 and refs. therein), and the
western Himalaya (Draganits, 2002; Singh, 2002). Should
we interpret the initial spreading of the Palaeo-Tethys
(sensu Metcalfe) amongst Chinese Blocks, propagating to
the west as far as the Karakoram and Himalaya, as
incipient rifting?
The major rift stage recorded by the North Karakoram
successions (Figs. 17 and 18) is in agreement with
subsurface and field evidence from Oman (Al-Belushi
et al., 1996) and from the Himalaya (Vannay, 1993;
Garzanti et al., 1996a; Garzanti and Sciunnach, 1997),
indicating that the Neo-Tethys rifting began as early as the
Early Carboniferous.
Finally, the interpretation of the Gircha Formation as
the unit that blankets the rifted margin within the
lowermost Permian is roughly in agreement with recent
data on the earlier spreading of the Neo-Tethys, from
Oman (Angiolini et al., 2001; Angiolini et al., 2003) to the
Himalaya (Garzanti et al., 1994; Garzanti et al., 1996b;
Garzanti et al., 1999) and SE Asia (Shi and Archbold,
1998) in the Early Permian. In the Karakoram this break-up
unconformity seems to be earlier, possibly because the
terrane was on the northern side of the Neo-Tethys and
already involved in earlier rifting events amongst the
Cimmerian blocks.
In conclusion, the Carboniferous succession records
the passive margin evolution of the Northern Karakoram
Terrane. A first episode of rifting is identified in the mid-
Givetian/Late Devonian, raising the question as to
whether the ocean drifting occurring at that time amongst
the Chinese Blocks (Metcalfe, 1996) was extended as
incipient rifting as far as the Karakoram. The early
rifting episodes continued in the Early Carboniferous,
evolving to the syn-rift stages during the Late Carbon-
iferous. The latest Carboniferous-earliest Permian basal
part of the Gircha Formation is considered to have been
deposited above the break-up unconformity, linked to an
early drifting event in the sea-way bordering the
Karakoram.
Acknowledgements
The 3 expeditions were funded by several grants to
M. Gaetani from the Italian Ministry for Foreign Affairs,
within a cultural agreement with the Government of
Pakistan. We are deeply indebted with Dr H. Gauhar,
Director of the Geological Survey of Pakistan, for
the continuous support to our investigations in the field.
Guides, cooks and porters of the Adventure Tours Pakistan
travel agency substantially helped in carrying out field-
activity in the high mountains.
The paper was Reviewed by A.H.F. Robertson
(Edinburgh) and by C. Winkler-Prins (Leiden). Both and
the Deputy-Editor, A.J. Barber, are deeply thanked for
important improvements to the paper.
Appendix A
The Fig. A1 illustrates the most significant conodont
specimens recovered from the Rabit Formation.
Appendix B
Selected palaeontological descriptions (L. Angiolini,
H. Brunton, G. Olivini)
All the described specimens are housed in the Palaeonto-
logical Museum of the University of Milan, Italy (MPUM
numbers). The systematic study follows the classifications of
Racheboeuf in Williams et al. (2000) for the chonetids, of
Brunton et al. in Williams et al. (2000) for the productids, of
Williams and Harper in Williams et al. (2000) for the orthids,
of Savage (1996) for the rhynchonellids, and of Carter et al.
(1994) for the spiriferids.
Family Rugosochonetidae Muir-Wood, 1962
Subfamily Rugosochonetinae Muir-Wood, 1962
Genus Rugosochonetes Sokolskaya, 1950
Type-species: Orthis hardrensis Phillips, 1841
Rugosochonetes sp. ind.
Material—2 ventral valve internal molds: MPUM9036
(CK1093-1,-2); 1 fragment of ventral valve: MPUM9037
(CK1093-3). Lupsuk Formation, Ribat section, Bashkirian.
Remarks—These slightly convex, finely capillate ventral
valves with no ventral sulcus and internally characterised by
a myophragm and coarse endospines indicates assignment
to Rugosochonetes.
Family Productellidae Schuchert, 1929
Subfamily Plicatiferinae Muir-Wood and Cooper, 1960
Tribe Yakovleviini Waterhouse, 1975
Genus Sajakella Nasikanova in Sarycheva, 1968
Type-species: Sajakella formosa Nasikanova, 1968
Sajakella sp. ind. (Fig. B1(1–2))
Material—1 articulated shell: MPUM9038 (KO14-f); 3
ventral valves: MPUM9039 (KO14 b,d), MPUM9040
(KO14e). Ribat Formation, Triple Junction section. Serpu-
khovian.
Remarks—Four valves characterized by a subovate to
subquadrate outline, a rugose and ribbed visceral disc
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UNCORRECTED PROOF
Fig. A1. Conodonts from the Ribat Formation. Specimens from CK 1089, housed in the Palaeontological Museum of the University of Milano. Scale bar
200 mm. 19/1a,1b, 2 Gnathodus typicus morph. 2 Cooper, 1939; respectively upper and lateral view. 19/3a,3b, 4 Polynatus bischoffi Rhodes, Austin and
Ziegler, 1969, respectively upper and lateral views. 19/5a,5b, 6 Gnathodus pseudosemiglaber Thompson and Fellow, 1970, respectively upper and lateral view.
Specimens from CK1125, housed in the Australian Museum, Sydney with the number prefixed AMF. The scale bar represents 100ıo. 19/7a,7b Gnathodus sp.
cf. G. delicatus Branson and Mehl, 1938. Upper and lateral views of AMF 121957. 19/8, 10 Gnathodus semiglaber Bischoff, 1957. Upper views of AMF
121958 and AMF 121959, respectively. 19/9 Gnathodus delicatus Branson and Mehl, 1938. Upper view of AMF 121960. 19/11 Gnathodus cuneiformis Mehl
and Thompson, 1947. Upper view of AMF 121961. 19/12-15 Gnathodus typicus Cooper, 1939. 12, 13: lateral and upper views of AMF 121962, respectively;
14, 15: lateral and upper views of AMF 121963, respectively. Non-platform elements of Gnathodus: 19/16 a M element; 19/17 a Sc element; 19/18 a ?Sa
element; 19/19 a Sb element.
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UNCORRECTED PROOF
and a finely ribbed trail have been placed in the upper
Visean- Bashkirian genus Sajakella. The ventral valve
shows a median sulcus, deeper anteriorly on the visceral
disc, and spines have been detected only at the cardinal
margin.
Family Productidae Gray, 1840
Subfamily Productinae Gray, 1840
Tribe Productini Gray, 1840
Genus Dowhatania Waterhouse in Waterhouse and
Gupta, 1979
Fig. B1. (All £ 1) (1) Sajakella sp. ind. Specimen MPUM9038 (KO14f). Ventral view of an articulated shell. (2) Sajakella sp. ind. Specimen MPUM9040
(KO14e). Ventral valve. (3) Dowhatania sulcata Angiolini and Brunton in Angiolini et al., 1999. Specimen MPUM9041 (CK1110b). Ventral valve. (4)
Marginoproductus ribatensis n. sp. Specimen MPUM9043 (KO20t), holotype. Ventral valve. (5) Marginoproductus ribatensis n. sp. Specimen MPUM9044
(KO20j). Ventral valve. (6) Marginoproductus ribatensis n. sp. Specimen MPUM9045 (KO20h). Ventral valve. (7) Marginoproductus ribatensis n. sp.
Specimen MPUM9046 (KO20z). Ventral valve. (8–9) Buxtonioides sp. ind. Specimen MPUM9095 (KO25-3g). Lateral and ventral view of a ventral valve.
(10) Marginovatia sp. ind. Specimen MPUM9050 (CK1094-1). Ventral view of an internal mold of an articulated shell. (11) Marginovatia sp. ind. Specimen
MPUM9051 (CK1093-6). Ventral valve. (12) Marginovatia sp. ind. Specimen MPUM9052 (CK1094-2). Dorsal valve external mold. (13) Cubacula sp. ind.
Specimen MPUM9054 (CK1139d). Ventral valve. (14) Rhynchopora sp. ind. Specimen MPUM9059 (CK1074-9). Dorsal valve. (15) Rhipidomella sp.1.
Specimen MPUM9055 (CK1074-2). Ventral valve and fragments. (16) Spirifer pentagonoides Plodowski, 1968. Specimen MPUM9066 (KO20-10). Ventral
valve. (17) Martiniopsis grandiformis (Plodowski, 1968). Specimen MPUM9064 (CK1103c). Ventral valve. (18) Spirifer pentagonoides Plodowski, 1968.
Specimen MPUM9067 (KO20-6). Ventral valve. (19) Spirifer pentagonoides Plodowski, 1968. Specimen MPUM9068 (KO20-16). Partially decorticated
ventral valve showing dental plates. (20) Spirifer pentagonoides Plodowski, 1968. Specimen MPUM9069 (KO20-19). Dorsal valve. (21) Spirifer
pentagonoides Plodowski, 1968. Specimen MPUM9070 (KO20-21). Dorsal valve.
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UNCORRECTED PROOF
Type-species: Productus dowhatensis Diener, 1915
Dowhatania sulcata Angiolini and Brunton in Angio-
lini et al., 1999 (Fig. B1(3))
1999 Dowhatania sulcata Angiolini and Brunton in
Angiolini et al., p. 11, pl. 1, figs. 1–10
Material—5 ventral valves: MPUM9041 (CK1110b),
MPUM9042 (CK1109A, CK1110a, c, d). Lupsuk For-
mation, W. Lupsuk section. Moscovian–Kasimovian.
Remarks—Dowhatania sulcata Angiolini and Brunton
in Angiolini et al., 1999 is characterized by its relatively
small size, posteriorly thickened shell, wide and sharp ears,
and deep ventral sulcus.
Tribe Retariini Muir-Wood and Cooper, 1960
Genus Marginoproductus Tan Zhen Xiu, 1986
Type-species: Marginoproductus hunanensis Tan Zhen
Xiu, 1986
Marginoproductus ribatensis n. sp. (Fig. B1(4–7))
Material—20 ventral valves: MPUM9043 (KO20t),
MPUM9044 (KO20j), MPUM9045 (KO20h), MPUM9046
(KO20z), MPUM9047 (KO20KO20c, g, l–n, p–r, s, u–v,
w, x, y, b1, b2, g); 4 dorsal valves: MPUM9048 (KO20d-f,
a). Ribat Formation, Laleribat 1, right topographical side of
Lale Ribat Valley, near the village. Visean.
Holotype: ventral valve, MPUM9043 (KO20t)
Stratum typicum: KO20, Ribat Formation
Locus typicus: locality Lale Ribat 1.
Derivatio nominis: ribatensis from the Ribat Valley.
Diagnosis—Small Marginoproductus with few spines
and fine costae.
Description—Shell concavo-convex, small, with sub-
quadrate outline. Corpus cavity deep. Ears small, well
demarcated from the flanks and angular. Ventral sulcus
absent; flanks parallel. Dorsal valve geniculated with
weakly concave visceral disc. Ornamentation of fine,
regularly spaced costae numbering 10 per 5 mm at 10 mm
from the umbo. Spines present in two symmetrical pairs on
the flanks; 2–3 coarse, erect spines occur at the junction
between the flanks and the ears. Few rugae may occur on
the flanks. Few longitudinal plications may occur anteriorly.
Interior of dorsal valve with traces of a sessile cardinal
process and lateral ridges.
Discussion—The peculiar subquadrate outline both in
posterior and anterior views and the number and
distribution of spines indicate that the KO20 specimens
belongs to the genus Marginoproductus Tan, well
described and figured from the Visean of the Shihtengtze
Formation of Cenral Hunan of South China (Tan, 1986, p.
435, pl. 1, fig. 33–40). Marginoproductus ribatensis n. sp.
differs from the type species by having fewer and smaller
spines, a near absence of rugae, and more numerous and
finer costae.
The specimens described as Tomiproductus elegantulus
(Tolmachev, 1924) from the Upper Tournaisian of the
Geirud Formation of N. Iran (Gaetani, 1968) are close to
the Karakoram species in their outline and the pattern of
ribbing and spines, but have a more marked reticulation
posteriorly on the ventral disc.
Subfamily Buxtoniinae Muir-Wood and Cooper, 1960
Genus Buxtonioides Mendes, 1959
Type-species: Productus amazonicus Katzer, 1903
Buxtonioides sp. ind. (Fig. B1(8–9))
Material-1 articulated shell: MPUM9094 (KO25-3c); 5
ventral valves: MPUM9049 (KO25-1b,-1e,-1f; KO25-2b),
MPUM9095 (KO25-3g). Ribat Formation, Karambar Pass
section. Bashkirian.
Description—Large, plano-convex shell with sub-trape-
zoidal outline and deep corpus cavity. Shell substance thick.
Ventral valve strongly convex with small, but well defined
ears. Ventral sulcus shallow, widening anteriorly, not well
differentiated from the flanks. Ornamentation of numerous,
fine, rounded costellae with angular intercostal furrows.
Irregular longitudinal plications may occur at the anterior
margin. Thin and low rugae are present on the flanks. Spines
irregularly scattered on the ventral valve.
Discussion—These specimens have been placed in the
Bashkirian-Gzhelian genus Buxtonioides based on their
shape and ornamentation.
Family Linoproductidae Stehli, 1954
Subfamily Linoproductinae Stehli, 1954
Genus Marginovatia Gordon and Henry, 1990
Type-species: Productus ovatus var. minor Snider, 1915
Marginovatia sp. ind. (Fig. B1(10–12))
Material—1 internal mold of a articulated shell:
MPUM9050 (CK1094-1); 2 external moulds of ventral
valves: MPUM9053 (CK1093-4,-5); 1 fragment of ventral
valve: MPUM9051 (CK1093-6); 1 dorsal valve external
mould MPUM9052 (CK1094-2). Lupsuk Formation, Ribat
section. Bashkirian.
Description—Large size for this genus (length exceeding
20 mm) with convex, enrolled ventral valve and concave
dorsal valve; outline longitudinally ovate. Ventral valve
ornamented by fine, sinuous costellae numbering 10–11 per
5 mm, with few and low rugae on the flanks, near ears; fine
spines sparse on the ventre. Dorsal valve ornamented by
costellae, rugae and elongated dimples. Interior of dorsal
valve with a submarginal ridge sorrounding the visceral disc.
Discussion—These specimens have been placed in
Marginovatia because of their ovate outline, ornamentation
of few spines and rugae and fine costellae and the internal
thickened ridge enclosing the dorsal visceral disc. Among
the North American species figured by Gordon and Henry
(1990), these specimens most resemble the Lower Pennsyl-
vanian M. aureocollis Gordon and Henry, 1990 by their
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UNCORRECTED PROOF
rugose dorsal ornamentation and the number of costellae,
despite being larger in size.
The genus Marginoproductus Tan, which also occurs in
Karakoram, has a marked subquadrate outline, a different
ornamentation and a high dorsal median septum.
Family Echinoconchidae Stehli, 1954
Subfamily Juresaniinae Muir-Wood and Cooper, 1960
Tribe Juresaniini Muir-Wood and Cooper, 1960
Genus Cubacula Lazarev, 1984
Type-species: Productus subpunctatus Nikitin, 1890
Cubacula sp. ind. (Fig. B1(13))
Material—1 ventral valve: MPUM9054 (CK1139-d).
Dark grey marly limestones at 4100 m of altitude on the
path leading to Siru An. Kasimovian.
Remarks—The species is represented by a single ventral
valve and is recognised by its ventral sulcus and
ornamentation of rugae and both suberect and recumbent
fine spines, regularly arranged in bands.
Family Rhipidomellidae Schuchert, 1913
Subfamily Rhipidomellinae Schuchert, 1913
Genus Rhipidomella Oehlert, 1890
Type-species: Terebratula michelini Leveille, 1835.
Rhipidomella sp. 1 (Fig. B1(15))
Material—4 ventral valves: MPUM9055 (CK1074-2),
MPUM9056 (CK1074-3,-4,-6); 1 dorsal valve: MPUM9057
(CK1074-5); various fragments and external casts of both
valves from the same level. Margach Formation, Ribat
section. Earliest middle Tournaisian.
Remarks—The genus Rhipidomella is here represented
by dorsibiconvex shells with a subcircular outline, orna-
mented by very fine ribs increasing up to 15–18 per 5 mm at
the anterior margin and widely spaced growth lamellae. The
ventral valve interior shows flabellate muscle scars bisected
by a median ridge.
They have been determined as Rhipidomella sp. 1 to
differentiate them from the other Rhipidomella species
(Angiolini et al., 1999, p. 14, pl. 1, fig. 15–17—referred to
as Rhipidomella sp. 2 in the biostratigraphic paragraph)
which comes from higher stratigraphic levels. In fact,
Rhipidomella sp. 1 differs from Rhipidomella sp. 2 in its
more rounded outline, narrower hinge, more numerous ribs
and absence of a sulcus in the dorsal valve.
Rhipidomella sp. 1 resembles the species called R.
michelini (Leveille, 1835) from the middle-upper
Tournaisian of the Murabak Limestone of N. Iran (Gaetani,
1968).
Family Rhynchoporidae Muir-Wood, 1955
Genus Rhynchopora King, 1865
Type-species: Terebratula geinitziana de Verneuil, 1845
Rhynchopora sp. ind. (Fig. B1(14))
Material—1 ventral valve external cast: MPUM9062
(CK1091-1); 5 dorsal valves: MPUM9059 (CK1074-9),
MPUM9060 (CK1074-8), MPUM9063 (CK1091-2,
CK1094-4,-5); 1 dorsal valve external cast: MPUM9061
(CK1074-7); several fragments: CK1073-2, CK1091-3,
CK1094. Margach and Lupsuk Formations, Ribat section.
Early Tournaisian-Bashkirian.
Remarks—The presence of the genus Rhynchopora is
indicated by the occurrence of several biconvex shells with
flaring outlines and with coarse ribs widening anteriorly,
numbering 4 on the fold, 5 on the sulcus and 5 on each flank.
Internally the ventral valve show traces of dental plates
whereas the dorsal valve shows the median septum
supporting the hinge plate.
Family Martiniopsidae Kotlyar and Popeko, 1967
Genus Martiniopsis Waagen, 1883
Type-species: Martiniopsis inflata Etheridge, 1892.
Martiniopsisgrandiformis(Plodowski,1968)(Fig.B1(17))
1968 Eomartiniopsis grandiformis Plodowski, p. 256,
pl. 1, fig. 9
1970 Eomartiniopsis grandiformis-Plodowski, p. 109,
text-fig. 54–56, pl. 8, fig. 5–7
1999 Martiniopsis sp.-Angiolini et al., p. 16, pl. 2, fig. 4–5
Material—1 articulated specimen: MPUM9065
(KO24d); 1 ventral valve: MPUM9064 (CK1103c).
Respectively from the Ribat Formation, E. Lupsuk section
and from scree of the middle part of the Ribat Formation in
the Lupsuk section. Visean.
Description—Biconvex shell with thick shell substance
and relatively wide-hinge. Maximum width around mid-
length. Anterior commissure uniplicate. Complete specimen
with elongate oval outline. Ventral valve convex with sub-
rhomboidal outline. Shell smooth, with narrow median
sulcus. Ornamentation of strong growth lines. Ventral
interior with dental plates. Dorsal interior with crural plates
and cardinal process in the form of a ctenophoridium.
Discussion—These specimens—and those previously
described from the scree of the Ribat Formation near
the Twin Valleys section (samples CK588, CK590 in
Angiolini et al., 1999)—are very close to Eomartiniopsis
grandiformis Plodowski, 1968 from the Goniatites-Stufe of
Burgutsch-Tal (Central Afghanistan) (Plodowski, 1970).
According to the accurate illustrations and description of
Plodowski (1968; 1970, p. 109, fig. 54–55), the species
grandiformis has short but thick crural plates which reach
the floor of the valve, thus differing from the type species of
Eomartiniopsis (E. elongata Sokolskaya, 1941) which has
no dorsal plates (Carter and Poletaev, 1998). Externally, E.
grandiformis is characterised by its large size and a
lamellose micro-ornamentation with sporadic occurrence
of small pits.
The martiniopsid species from Afghanistan is similar to
species of the genus Crassumbo Carter, 1967, which,
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UNCORRECTED PROOF
however, differs by its capillate micro-ornamentation and a
median ridge inside the ventral valve of the juveniles.
Chuiella Chen and Shi, 1999 from the Lower Carboniferous
of NW China (Chen and Shi, 1999) is also similar, but has a
median ridge in the ventral valve interior.
Because of the combination of internal and external
characters the species grandiformis is provisionally trans-
ferred to the genus Martiniopsis, which, however, has
longer dorsal plates and a pustulose micro-ornamentation,
and we do not not exclude the possibility that the Afghan
and Karakoram species may represent a new genus.
Family Spiriferidae King, 1846
Subfamily Spiriferinae King, 1846
Genus Spirifer Sowerby, 1816
Type-species: Conchyliolithus (Anomites) striatus Mar-
tin, 1809
Spirifer pentagonoides Plodowski, 1968 (Figs. B1(16,
18–21) and B3(11–14))
1968 Spirifer pentagonoides Plodowski, p.253, pl. 1, fig. 3
1970 Spirifer pentagonoides-Plodowski, p. 64, text-fig.
32–36, pl. 1,. fig. 11–12, pl. 2, fig. 1–5, pl. 12, fig. 1
Material—1 articulated shell: MPUM9072 (KO20-1); 17
ventral valves: MPUM9066 (KO20-10), MPUM9067
(KO20-6), MPUM9068 (KO20-16), MPUM9071 (KO20-
2,-3,-5,-7,-8,-9,-11,-12,-13,-14,-15,-17,-18,-20); 2 dorsal
valves: MPUM9069 (KO20-19), MPUM9070 (KO20-21).
Ribat Formation, Lale Ribat 1, right topographical side of
Lale Ribat Valley, near the village. Visean.
Description—Biconvex shell, with slightly transverse
subpentagonal outline. Cardinal extremities angular. Ven-
tral interarea concave, high with wide delthyrium. Ventral
sulcus shallow, widening anteriorly, ornamented by 3–4
broad ribs anteriorly. Dorsal fold well defined, anteriorly
elevated forming a broad arch.
Ornamentation of coarse rounded ribs, with narrow
intercostal furrows. Ribs increase in width anteriorly and
number 4 per 5 mm at 10 mm from the umbo and about 2–3
per 5 mm at the anterior margin. Interior of ventral valve
with apical callus, small delthyrial plate and strong, straight
and slightly divergent dental plates.
Discussion—These numerous and reasonably well pre-
served specimens share the specific characters of the Spirifer
pentagonoides Plodowski, 1968 from the Visean Goniatites-
Stufe of Burgutsch-Tal (Central Afghanistan). The species is
characterised by its outline, the coarse ribbing, details of the
dorsal fold and the internal morphology of the ventral valve.
Spirifer subgrandiformis Plodowski, 1968 (Fig. B2(1))
1968 Spirifer subgrandiformis Plodowski, p. 254, pl. 1,
fig. 1
1970 Spirifer subgrandiformis-Plodowski, p. 60, text-
fig. 29–31, pl. 5, fig. 5–8, pl. 6, fig. 1–3.
Material—1 articulated shell: MPUM9073 (KO24a).
Ribat Formation, E. Lupsuk section. Visean.
Description—Large sized (W: 64.9 mm; L: 40.3 mm)
with transverse, subpentagonal outline. Shell substance
thick. Anterior commissure uniplicate; cardinal extremities
alate. Ventral interarea high. Ventral sulcus shallow,
subangular. Dorsal fastigium widening and elevating
anteriorly. Ornamentation of rather coarse, irregularly
bifurcating costae, numbering 6–8 per 10 mm at 10 mm
from the umbo.
Discussion—This specimen is assigned to S. subgran-
diformis because of its dimensions, profile, ornamentation
and shape of the sulcus. S. subgrandiformis has been
found in the Visean Goniatites-Stufe of Central Afghani-
stan. Legrand-Blain (1986) reports Spirifer aff. subgran-
diformis from the early to early late Visean of the
Algerian Sahara.
Spirifer cf. S. denis (Beznosova, 1959) (Fig. B2(2))
Material—1 ventral valve: MPUM 8383 (CK588-2).
Scree of the Ribat Formation near the Twin Valleys section.
Remarks—This convex ventral valve, with a shallow and
narrow sulcus, ornamented by numerous bifurcating, rarely
trifurcating, ribs numbering 10–11 per 10 mm at 15 mm
from the umbo and growth lamellae is close to the
specimens figured as Spirifer denis from the Visean
Goniatites-Stufe of Central Afghanistan (Plodowski, 1970,
p. 75, pl. 2, fig. 6–8).
Genus Ectochoristites Campbell, 1957
Type-species: Ectochoristites wattsi Campbell, 1957
Ectochoristites sp. ind. (Figs. B2(3–4) and B3(7–10))
Material—1 articulated shell: MPUM9074 (KO14a).
Ribat Formation, Triple Junction section. Serpukhovian.
Description—Biconvex, elongated shell (W: 27.4; L:
32.6) with narrow cardinal margin and slightly alate
cardinal extremities. Anterior commissure uniplicate.
Shell substance thick. Ventral umbo incurved over
the interarea. Ventral sulcus deep, ‘V’ shaped. Dorsal
fastigium low. Ornamentation of sparce, rounded costae,
numbering about 4 per 5 mm at the anterior margin of the
dorsal valve and growth lamellae.
Interior of ventral valve with thickened dental plates,
divergent to the valve floor and united to the valve walls by
a callus; dental flanges close medianly up to 6.4 mm from
the umbo, forming an angle with the ventral adminicula
which extend up to 7.2 mm from the umbo.
Discussion—This single specimen is well preserved and
indicates the occurrence of the Tournaisian-?Namurian genus
Ectochoristites in Karakoram. It is characterized by an
elongate outline, rounded costae and divergent dental plates.
A species of Ectochoristites has been reported by Yang
and Fan (1983) from the Visean Eastern Baria Member of
Yungzhu, Xainza County (Central Tibet).
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UNCORRECTED PROOF
Subfamily Prospirinae Carter, 1974
Genus Parallelora Carter, 1974
Type-species: Spirifer marionensis Shumard, 1885
Parallelora aff. subsuavis (Plodowski, 1968)
(Fig. B2(5–6))
Material—4 ventral valves: MPUM9075 (CK1075-1,-2),
MPUM9076 (CK1073-1), MPUM9077 (CK1077-1); 1
dorsal valve: MPUM9058 (CK1074-1). Margach For-
mation, Ribat section. Earliest middle Tournaisian.
Description—Transverse, biconvex with moderately
developed fold and sulcus. Lateral slopes ornamented
by fine rounded costae. Costae seem to bifurcate on the
flanks resulting in more than 17 ribs on each slope at
10 mm from the umbo. Ventral sulcus ornamented by a
median simple costa and 2–3 ribs on each side. Fold
delimited by deep grooves and ornamented by 9 ribs.
Interior of ventral valve with dental plates formed by
thick dental flanges and thin divergent ventral
adminicula.
Fig. B2. (All £ 1) (1) Spirifer subgrandiformis Plodowski, 1968. Specimen MPUM9073 (KO24a). Ventral view of an articulated shell. (2) Spirifer cf. S. denis
(Beznosova, 1959). Specimen MPUM8383 (CK588-2). Ventral valve. (3–4) Ectochoristites sp. ind. Specimen MPUM9074 (KO14a). Ventral and dorsal view
of an articulated shell. (5) Parallelora aff. subsuavis (Plodowski, 1968). Specimen MPUM9075 (CK1075-1). Ventral valve. (6) Parallelora aff. subsuavis
(Plodowski, 1968). Specimen MPUM9058 (CK1074-1). Dorsal valve with a fragment of Rhipidomella sp.1. (7) Afghanospirifer cf. burgutschensis Plodowski,
1968. Specimen MPUM9078 (KO18e). Ventral view of an articulated shell. (8) Anthracospirifer sp. ind. Specimen MPUM9082 (KO15a). Dorsal valve. (9)
Choristites sp. ind. Specimen MPUM9084 (KO23h). Ventral valve. (10) Choristites sp. ind. Specimen MPUM9085 (KO23g). Ventral valve. (11) Syringothyris
sp. ind. Specimen MPUM9093 (KO15b). Partially decorticated dorsal valve. (12) Gypospirifer sp. ind. Specimen MPUM9089 (KO22-2). Ventral view of an
articulated shell. (13–15) Gypospirifer sp. ind. Specimen MPUM9088 (KO22-1). Ventral, dorsal, posterior views of an articulated shell.
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UNCORRECTED PROOF
Discussion—These specimens are very similar to those
described as Spirifer subsuavis Plodowski (1968, p. 253, pl. 1,
fig. 5; 1970, p. 52, pl. 1, fig. 5–10, pl. 11, fig. 2), but they lack
the apical callus and they have longer dental plates and a more
convex ventral valve. The species subsuavis seems to be
characterized by its rectangular ventral interarea, clearly
delineated fold and sulcus, and its moderately numerous
bifurcating costae, features indicative of the late Devonian–
early Tournaisian genus Parallelora Carter, 1974.
Subfamily Sergospiriferinae Carter, Johnson, Gourven-
nec, Hong-Fei 1994
Genus Afghanospirifer Plodowski, 1968
Type-species: Afghanospirifer burgutschensis Plo-
dowski, 1968
Afghanospirifer cf. burgutschensis Plodowski, 1968
(Fig. B2(7))
1999 Afghanospirifer sp.-Angiolini et al., p. 16, pl. 2, fig.
6–7, text-fig. 6a.
Material—2 articulated shells: MPUM9078 (KO18e),
MPUM9079 (KO17a); 2 ventral valves: MPUM9080
(KO23b,f); 3 dorsal valve: MPUM9081 (KO23c,e;
CK1094-3). Ribat and Lupsuk Formations, Triple Junction,
Ribat and Karambar Lake sections. Bashkirian.
Description—Biconvex shell with subrectangular out-
line; dimensions: widths of 34.3 and 38.8 mm; correspond-
ing lengths: 22.8 and 27.3 mm. Cardinal extremities
rounded to slightly pointed. Ventral interarea relatively
high, concave, denticulated. Ventral sulcus shallow. Flanks
ornamented by few, coarse, rounded, bifurcating ribs with
narrow intercostal furrows, numbering 3–4 per 5 mm at
15 mm from the umbo and close growth lamellae. Fold
ornamented by 3–4 ribs.
Discussion—As already pointed out by Angiolini et al.
(1999), based on material from the Twin Valleys section, the
Karakoram specimens attributed to the Serpukhovian-lower
Bashkirian genus Afghanospirifer are not well preserved.
However, based on these new findings, they probably belong
to A. burgutschensis Plodowski, 1968 as no significant
characters differentiate them from the type-species.
Genus Anthracospirifer Lane, 1963
Type-species: Anthracospirifer birdspringensis Lane,
1963
Anthracospirifer sp. ind. (Fig. B2(8))
Material—2 dorsal valves: MPUM9082 (KO15a),
MPUM9083 (CK1101). Ribat Formation, Triple Junction
section and from scree of the Ribat Formation in the Lupsuk
section. Serpukhovian.
Remarks—Two specimens indicate the possible occur-
rence of the Serpukhovian–Bashkirian genus Anthracospir-
ifer. They are dorsal valves with subangular folds
ornamented by a median costa and a pair of bifurcating
lateral ribs; flanks ornamented by coarse, rounded costae
widening anteriorly up to 1.4 mm in width at the anterior
margin with narrow intercostal furrows.
Family Choristitidae Waterhouse, 1968
Subfamily Choristitinae Waterhouse, 1968
Genus Choristites Fischer de Waldheim, 1825
Type-species: Choristites mosquensis Fischer de Wald-
heim, 1825
Choristites sp. ind. (Figs. B2(9–10) and B3(1–6))
1999 Choristites sp.-Angiolini et al., p. 17, pl. 2,
fig. 8–10
Material—1 articulated shell: MPUM9086 (KO16); 4
ventral valves: MPUM9084 (KO23 h), MPUM9085
(KO23 g), MPUM9087 (KO23 l, KO17c). Ribat Formation,
Karambar Lake section and Triple Junction section.
Bashkirian.
Description—Large, biconvex shell with subpentagonal
outline and maximum width at 1/3 the shell length. Interarea
low, concave, trapezoidal and denticulate. Ventral valve
strongly convex especially posteriorly, with incurved umbo
and wide ventral sulcus, deepening anteriorly, ornamented
by a median costa and 3 to 4 ribs on each side. Each ventral
flank ornamented by flat, bifurcating ribs, numbering about
4 per 5 mm at 20 mm and from the umbo. Strong growth
lines also occur.
Interior of ventral valve with slightly divergent dental
plates and elongate oval, depressed muscle field delimited
by rounded ridges.
Discussion—The specimens are similar to Choristites
xainzangensis Yang, 1983 from the middle Carboniferous
Sisuo Formation, Yungzhu, Xainza County (Central Tibet)
(Yang and Fan, 1983), as are those described by Angiolini
et al. (1999) from the Twin Valleys section. They differ by
having a more convex ventral umbo.
Family Trigonotretidae Schuchert, 1893
Subfamily Neospiriferinae Waterhouse, 1968
Genus Gypospirifer Cooper and Grant, 1976
Type-species: Gypospirifer nelsoni Cooper and Grant,
1976.
Gypospirifer sp. ind. (Fig. B2(12–15))
1999 Gypospirifer sp.-Angiolini et al., p. 18, pl. 2, fig.
11–12, text-fig. 6b
Material—3 articulated shells: MPUM9088 (KO22-1),
MPUM9089 (KO22-2), MPUM9090 (KO22-3); 5 ventral
valves: MPUM9091 (KO17e,f,g; KO18f; KO23d). Ribat and
Lupsuk Formations, Triple Junction section, Karambar Lake
section, scree from the Ribat Formation in the Tarsan Valley
near Ribat village. Bashkirian.
Description—Biconvex shells, with transverse semicir-
cular outline; maximum width at the hinge, cardinal
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UNCORRECTED PROOF
extremities angular. Ventral interarea wide, denticulate.
Ventral sulcus narrow and shallow. Ornamentation of fine,
rounded, bifurcating ribs, numbering 5–6 per 5 mm at
10 mm from the umbo. Faint traces of ribbing fasciculation
occur posteriorly. Sulcus ornamented by a median rib
bifurcating anteriorly and 2–3 ribs on each side bifurcating
from the costae bordering the sulcus. Interior of ventral
valve with a small delthyrial plate, thin dental flanges, short
adminicula and sub-rhomboidal muscle-field. Interior of
dorsal valve with ctenophoridium.
Discussion—As already stated by Angiolini et al. (1999),
the poor preservation of the Karakoram specimens prevent
an accurate specific assignment. However, the morphologi-
cally nearest species are Gypospirifer guelmounensis
Fig. B3. (1–6) Choristites sp. ind. Specimen MPUM9086 (KO16), serial sections at 4.4, 6.7, 8.0, 9.2, 9.2, 9.8 mm from the umbo. Figs. 1-2 £ 4; figs. 3-4,
6 £ 3; 5 £ 6. 22.7–10 Ectochoristites sp. ind. Specimen MPUM9074 (KO14a), serial sections at 3.6, 5.3, 6.4, 7.2 mm from the umbo. All £ 4. 11–14. Spirifer
pentagonoides Plodowski, 1968. Specimen MPUM9071 (KO20-17), serial sections at 3.5, 5.7, 6.9, 8.1 mm from the umbo. All £ 4.
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Legrand-Blain, 1986 from the Visean-Serpukhovian of the
Algerian Sahara and G. anancites Cooper and Grant, 1976
from the Pennsylvanian-Lower Permian of West Texas.
Family Syringothyridae Frederiks, 1926
Subfamily Syringothyridinae Frederiks, 1926
Genus Syringothyris Winchell, 1863
Type-species: Syringothyris typa Winchell, 1863
Syringothyris sp. ind. (Fig. 21.11)
Material—2 ventral valves: MPUM9092 (KO25c, d).
Ribat Formation; 1 dorsal valve: MPUM9093 (KO25b).
Karambar Pass section. Bashkirian.
Remarks—These specimens show ventral valves with a
high, triangular, slightly concave interarea with an apical
angle of about 1208 and a large delthyrium internally closed
by a delthyrial plate with a syrinx. Ventral sulcus shallow,
diverging at 308. Flanks ornamented by flat-topped costae.
Interior with long diverging dental plates. The partially
decorticated dorsal valve has a large fold and flanks each
ornamented by about 17 flat-topped costa. Internally a long
median myophragm occurs.
They are rather similar to Syringothyris sp. 2 described
by Plodowski (1970, p., pl. 8, fig. 10) from the late
Serpukhovian–early Bashkirian of Burgutsch-Tal (13 km
SW Bukhara-e-Nawar, Central Afghanistan).
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