A N N A L E S H I S T O R I C O - N A T U R A L E S M U S E I N A T I O N A L I S H U N G A R I C I Volume 90. Budapest, 1998 pp. 35-55.

Early Jurassic brachiopods from the basal layers of the Pisznice Limestone of Lábatlan (Gerecse Mts, Hungary)

A. DULAI

Department of Geology and Paleontology Hungarian Natural History Museum

H-1431 Budapest, P. O. Box 137, Hungary

D U L A I , A. (1998): Early Jurassic brachiopods from the basal layers of the Pisznice Limestone of Lábatlan (Gerecse Mts., Hungary). - Annls hist.-nat. Mus. natn. hung. 90: 35-55.

Abstract - This is the first detailed (taxonomical, taphonomical, paleoecological, stratigraphical) study of the Early Jurassic brachiopods of the eastern Gerecse Mts. A rich, Mediterranean-type Early Liassic (probably Late Hettangian-Early Sinemurian) brachiopod fauna was collected bed-by-bed from the Tölgyhát quarry and a section at Póckő. The lowest 3.5 m of the Pisznice Lime­stone yielded 17 species of rhynchonellids, spiriferids and tcrebratulids. Four additional brachiopod species were found in the collection of the Hungarian Geological Institution from Póckő. The geo­logical setting of these localities (significant distance from seamounts, basin-type sedimentation) and the low ratio of disarticulated valves suggest that the brachiopods were not transported from a seamount. Therefore the brachiopod fauna of these layers represents the composition of an Early Jurassic moderate to deep-water community. On the basis of the stratigraphie distribution of the brachiopod species, the examined layers at Tölgyhát and Póckő, can probably be correlated with the lower, thick-bedded part of the Jurassic section of Vöröshíd quarry near Tardos. With 17 figures.

I N T R O D U C T I O N

The Gerecse Mts are situated at the northeastern part of the Transdanubian Central Range. The southern part of the mountains are underlain by exclusively Triassic forma­tions. Younger Mesozoic (Jurassic and Cretaceous) rocks are exposed only at the north­ern part of the area ( V É G H - N E U B R A N D T 1960).

The Lofer-cycles of the Upper Triassic Dachstein Limestone are well-correlated along great distances ( H A A S 1988). On the other hand, the Lower Jurassic formations, which unconformably overlie the Triassic limestone, show much greater variability which suggests that the uniform carbonate platform, evolved at the end of the Triassic, started to subside differentially during the Early Jurassic. Various blocks subsided at dif­ferent rates, leading to the development of relatively emerged seamounts and intervening basins ( G A L Á C Z & V Ö R Ö S 1972, V Ö R Ö S & G A L Á C Z 1998). The tectonic collapse of the

platform probably started already during the Hettangian in the Bakony Mts ( D U L A I 1993«). On the basis of facies differences among and within the Jurassic formations, the

Gerecse Mts were subdivided into two part by V Í G H (1961): central and eastern Gerecse, and western Gerecse. The boundary between the two areas is running approximately along the road between the villages of Süttő and Tardos. The Jurassic sediments of the western Gerecse were deposited on an emerged seamount, while the eastern Gerecse is characterized by basin-type sediments.

The Early Jurassic brachiopods were only studied in the western Gerecse, mainly from the extremely rich Hierlatz-type limestones, and in the Kálvária H i l l at Tata. H O F -M A N N ( 1884) published the first list of fauna and the description of a new species. K O C H

(1909) listed 19 Liassic brachiopod species from the Kálvária H i l l . K U L C S Á R (1914) figured several species from the Gerecse Mts. V Í G H (1943) described 61 brachiopod species from the Sinemurian and Pliensbachian deposits of the western Gerecse. V Í G H in F Ü L Ö P (1975) listed 41 Early Liassic brachiopod species from the Kálvária H i l l .

Despite these previous reports, the Early Jurassic brachiopod fauna of the eastern Gerecse is still poorly known. The aim of this paper to present the brachiopod faunas from two classical localities in the eastern Gerecse (Tölgyhát quarry and Póckő), which are very near to each other, south of the town of Lábatlan (Fig. 1 ). The second purpose of

Fig. 1. Sketch map showing the location of the studied localities ( 1 - Tölgyhát quarry, 2 - Póckő, 3 - Vöröshíd quarry).

this work is to make a comparison between the fauna of the Lábatlan localities and the fauna of the Vöröshíd quarry at Tardos. The brachiopods were collected from the basal layers of the oldest Jurassic formation (Pisznice Limestone Formation). The knowledge of the brachiopods of these layers is particularly important, since determinable am­monites are missing from these layers. So the brachiopods are the only megatbssils and therefore they are stratigraphically significant.

Figs 2-3. Tölgyhát quarry: 2 = the studied section of the Pisznice Limestone, 3 = stratigraphie dis­tribution of the determined species within the studied layers (width of vertical bars: 1 mm = I spe­cimen)

T H E L O C A L I T I E S A N D THEIR F A U N A S

Tölgyhát quarry

The topmost layers of the Upper Triassic Dachstein Limestone can be seen at the base o f the classical Tölgyhát quarry, in about 3 meter thickness. This limestone is un-conformably overlain by a thick, more or less continuous Jurassic section. The lowest formation of the Jurassic is the Pisznice Limestone, a reddish-grey, splinterly breaking limestone. Its microfacies is onkointrabiosparite wi th biomicrite mottles (KONDA 1988). The lower part o f the formation is poorly layered and contains small intraclasts at some places.

The fauna of this limestone includes crinoid fragments, benthic foraminifers, ostra-cods, brachiopods, gastropods and juvenile ammonoids seen only in polished or thin sec­tions (KONDA 1988). Brachiopods are the only determinable megafossils in the basal layers of the Pisznice Limestone. According to K O N D A (1988), these layers deposited in a high-energy environment. The age of this formation was determined by G. VÍGH (in KONQA 1988) as Middle Hettangian to Sinemurian, although no fossils were mentioned.

The examined brachiopods were collected by the author from the lowest 3.5 meters of the Pisznice Limestone. This part of the formation is very thick-bedded and this part of the section can only be divided into two different layers (Fig. 2). The fol lowing brachio­pod species were determined (the number of specimens is given in brackets):

Layer 1

Calcirhynchia plicatissima ( Q U E N S T E D T )

Cuneirhynchia cartieri (OPPEL) (11)

(3)

(8)

(1)

(1)

(1)

(4)

(1)

(1)

(2)

(23)

Rhynchonellida indet.

Liospiriferina alpina (OPPEL)

Liospiriferina guembeli ( N E U M A Y R )

Spiriferida indet

Phymatothyris aft. cerasulum (ZlTTEL)

Zeilleria cf. alpina ( G E Y E R )

Zeillena mutabilis (OPPEL)

Zeilleria choffati ( H A A S )

Terebratulida indet.

Layer 2

Calcirhynchia plicatissima ( Q U E N S T E D T )

Cuneirhynchia cartieri ( O P P E L )

(1)

(3)

(13)

(1)

(6)

(4)

Rhynchonellida indet.

Liospiriferina alpina (OPPEL)

Spiriferida indet.

Phymatothyris aff. cerasulum (ZlTTEL)

Zeilleria mutabilis (OPPEL) ( 1 )

Zeilleria cf. balilla ( G E Y E R ) (3)

Zeilleria sp. (2)

Terebratulida indet. (26)

The distribution of the determined species along the examined section is shown on Fig. 3.

Póckő

This locality is situated only a few hundred meters from the Tölgyhát quarry, there­fore the features o f the Pisznice Limestone are very similar. However, a remarkable dif­ference is that the formation is thinner-bedded here, so four layers can be distinguished within the same thickness of section (about 3.5 meters) (Fig. 4).

About 20 brachiopod specimens can be found in the collection of the Hungarian Ge­ological Institution from the Póckő locality, which represent a fairly diverse fauna (11 species). These specimens were collected by K . K U L C S Á R , G Y . V Í G H and E . V A D Á S Z in the first half of the 20th century. The determined species as revised by the present author, are the following:

Cirpa latifrons (S'lUR in G E Y E R ) (1)

Cirpa cf. variabilis ( S C H L O T H E I M ) (1)

Calcirhynchia plica!issima (QUENSTEDT) (1) Prionorhynchia pseudopolyptycha (Bi)CKH) (1) Cuneirhynchia fraasi (OPPEL) (1)

Liospiriferina alpina (OPPEL) (1)

Liospiriferina guembeli ( N E U M A Y R ) (1)

Liospiriferina sp. (2)

Koninckodonta sp. (1)

Linguithyris aspasia (MENEGHINl) (1) Zeilleria mutabilis (OPPEL) (3)

Zeilleria venusta ( U H L I G ) (1) Zeilleria choffati ( H A A S ) (2)

Zeilleria sp. (2)

Rakonyilhyris sp. 0 )

Unfortunately, the exact stratigraphie position o f these specimens is unknown within the Póckő section. Therefore, in the following discussion only those specimens w i l l be taken into consideration, which were collected bed-by-bed by the author. The specimens in the collection of the Hungarian Geological Institution w i l l only be mentioned in some

AnnLs hist.-nat. Mus. natn. hung. 90, 1998

cases in the Paleontological Notes. During the new collection, the following brachiopod taxa were found in the lowest four layers of Póckő locality:

Layer 1

Calcirhynchia plicatissima (QUENSTEDT) (6 )

Calcirhynchia laevicosta (STUR in GEYER) (!)

Salgirella albertii (OPPEL) (1) Prionorhynchia cf. greppini (OPPEL) (1) Prionorhynchia sp. (2 )

Cuneirhynchia cartieri (OPPEL) (4)

Rhynchonellida indet. (4)

Liospiriferina sp. (1) Spiriferida indet. (2 )

Koninckodonta sp. (5)

Phymatothyris aff. cerasulum (ZlTTEL) (2)

Zeilleria cf. mutabilis (OPPEL) (1) Terebratulida indet. (11)

Layer 2

Calcirhynchia cf. plicatissima ( Q U E N S T E D T )

Prionorhynchia cf. greppini ( O P P E L )

Terebratulida indet.

Layer 3

Calcirhynchia plicatissima ( Q U E N S T E D T )

Calcirhynchia fascicostata ( U H L I G )

Priono rl tyncl i ia s p.

Cuneirhynchia cartieri ( O P P E L )

Cuneirhynchia fraasi ( O P P E L )

"Rhynchonella" triquetra G E M M E L L A R O

Rhynchonellida indet.

Lobothyris andleri ( O P P E L )

Terebratulida indet.

Layer 4

Calcirhynchia cf. plicatissima ( Q U E N S T E D T ) (3 )

Cuneirhynchia cartieri ( O P P E L ) ( 1 )

"Rhynchonella" triquetra G E M M E L L A R O (4)

Rhynchonellida indet. (7 )

Liospiriferina alpina ( O P P E L ) (2 )

(1)

( 1 )

( 1 )

(2)

(1)

(2)

(1)

(2 )

(1)

(4)

(1)

(3 )

Annls hist.-nat. Mas. natn. hung. 90, 1998

Liospiriferina aradasi (GEMMELLARO) ( 1 )

Liospiriferina sp. (2 )

Spiriferida indet. (2 )

Lobothy ris an die ri (OPPEL) (2 )

Phymatothyris aff. cerasulum (ZlTTEL) (24)

Zeilleria cf. alpina (GEYER) ( I )

Zeilleria cf. choffali ( H A A S ) (3)

Terebratulida indet. (45)

The distribution of the determined species within the examined section is shown on Fig. 5.

Salgirella albertii Calcirhynchia laevicosta

Koninckodonta sp.

Zeilleria mutabilis Prionorhynchia cf. greppini Prionorhynchia sp.

Calcirhynchia plicatissima

Cuneirhynchia cartieri

liospiriferina sp.

Phymatothyris aff. cerasulum g

Calcirhynchia fascicostata Cuneirhynchia fraasi "Rhynchonella" triquetra Lobothyris andleri Zeilleria alpina Zeilleria choffati Liospiriferina alpina Liospiriferina aradasi

Figs 4 - 5 . Póckő: 4 = the studied section o f the Pisznice Limestone, 5 = stratigraphie distribution ol the determined species wi th in the studied layers (width o f vertical bars: 1 mm = 1 specimen)

BRACHIOPOD D I V E R S I T Y A N D A B U N D A N C E

The number ot" specimens is shown on Fig. 6. Nearly the same number o f brachio­pod specimens was found in both layers of the Tölgyhát quarry (60 and 56 specimens re­spectively). However, more than half of the specimens in the layer 1 and 3/4 of the speci-

Tölgyhát quarry Póckő

mens in the layer 2 are undeterminable fragments. The reason of the high number of un­determinable specimens is that the recovery of fossils from the Pisznice Limestone is very difficult. Nevertheless, a diverse brachiopod fauna occurs at this locality: the deter­minable 24 and 15 specimens represent 5 genera in both layers with 8 and 7 species, re­spectively (Fig. 7).

Approximately half of the specimens are also undeterminable at Póckő . The number of specimens is the highest in layer 4 (97), relatively high in layer 1 (41), small in layer 3 (17) and only three specimens were found in layer 2 (Fig. 6). In spite of this uneven dis­tribution, the diversity shows a more balanced picture (Fig. 7). The number of species and the number o f genera is nearly the same in layers 1, 3 and 4. I t is interesting that the number of species and the number o f genera is slightly higher in layer 1 than in layer 4 . although the number o f specimens is about the half in layer 1. I t is also remarkable, that the 10 determinable specimens from layer 3 represent 7 species: a relatively high diver­sity is accompanied by low abundance.

T A X O N O M I C COMPOSITION OF T H E F A U N A

Terebratulids are the predominant elements of the fauna and rhynchonellids are also frequent in the Tölgyhát quarry (Fig. 8). Spiriferids are insignificant in layer 1 but slight­ly more frequent in layer 2. The abundance of terebratulids is nearly the same in both layers, so the increase of the number of spiriferids coincides with the decrease of the number of rhynchonellids.

A t Póckő, the distribution of brachiopod orders is more varied. Layer 2 is left out of consideration because of its very small number of specimens. The ratio of rhynchonellids and terebratulids is nearly the same in layer 1 (about 50%). Three-fourth of the speci­mens belong to rhynchonellids in layer 3 but the ratio of rhynchonellids decreases drasti­cally in layer 4, where the terebratulids become the predominant group. Spiriferids are practically missing from layers 1, 2 and 3 and constitute a more significant group only in layer 4.

T A P H O N O M I C A L A N D P A L E O E C O L O G I C A L FEATURES OF T H E F A U N A

Ratio of disarticulated valves

The proportion o f disarticulated valves is very small (14%) in layer 1 of the Tölgy­hát quarry, but rather high (60%) in layer 2 (Fig. 9). The ratio of disarticulated valves is also increased in the upper layers o f the section at Póckő, where the same thickness can be divided into more layers. The increase is gradual, but the two extremes of the interval are closer to one another: not so small at the bottom and not so high at the top of the sec­tion than in the Tölgyhá t quarry (layer 1: 2 1 % ; layer 2: 33%; layer 3: 35%; layer 4: 45%). The average ratio of disarticulated valves is nearly the same at both localities (Tölgyhát quarry: 37%; Póckő: 38.5%).

Sparitic infilling of brachiopods

The brachiopod shells are infilled partly by micritic lime mud and partly by coarse­grained sparry calcite. The examination o f their ratio may be indicative of the sedimenta­tion rate.

The percentage of sparitic inf i l l ing is 56.3% in layer 1 and 25% in layer 2 of the Tölgyhát quarry (Fig. 10). So the proportion of sparry calcite dropped to less than half in the higher part of the examined section.

Tölgyhát quarry Póckö

4 0 %

6 0 % °/ / o

11

Figs 9-11. 9 = ratio of disarticulated valves, 10 = sparitic infilling of brachiopod shells, 11 = mean size of brachiopods

The sparite-micrite ratio is 50.3% in layer I of Póckő, similarly high as in the lower layer of the Tölgyhát quarry. The matrix is entirely micritic in layer 2 of Póckő, although only three specimens were found from here. The percentage of sparitic infi l l ing is de­creased in layers 3 and 4 of Póckő (37.5% and 35% respectively), but not as significantly as at the other locality.

5 m 12

Dachstein Limestone

13

p , w cd

Ü

R M >-15 c

S3 bû tu h ou

Xt on

•*-» o o

KJ oo CL)

bű JD 0)

Cd «1 •g cd

S :s S eu

N Q

.2 g o

I -c ? CD

«•H - n 2 3 U

O

3

cd

cj tí

s -"o 3

U

ö o

O

tí ' 5

c

cd

CD

c r

j d

ö o o

23 o

O h P 3

10 1 9 • W 1 8 T • 1 7

6 1 1 5 A • 4 3 I — W E — • — 1 — • — w m — W Ê m ^ ^ m •

... M 2

1 1 ™ • 1 • _ _ J i ^ ^ p M _ _ J L

1

Figs 12-13. Vöröshíd quarry: 12 = the lower part of the studied section of the Pisznice Limestone, 13 = stratigraphie distribution of the determined species within the lower part of the studied layers (width of vertical bars: 1 mm = 1 specimen)

A characteristic feature at both localities, that the proportion of sparry calcite is either 0% or 100% at the majority of the specimens, i.e. these brachiopods are infilled en­tirely by micritic lime mud or entirely by coarse-grained sparry calcite. Sparitic inf i l l ing is between 10% and 90% only at a few specimens, i.e. these brachiopods are only par­tially infilled by sparry calcite.

Size distribution of brachiopods

The mean maximum size of brachiopods found in different layers was calculated (Fig. 11). The mean size is 8.4 mm in layer 1 and 10.1 mm in layer 2 of the Tölgyhát quarry, i.e. the mean size is larger at the higher part o f the section. The specimens of Cal­cirhynchia plicatissima and Cuneirhynchia cartieri show sizes around the mean values. The specimens of the genera Zeilleria and Liospiriferina are larger, while the specimens of Phymatothyris aff. cerasulum and the undeterminable specimens of Terebratulida are smaller than the mean size of the locality.

The mean size of the specimens is 8.1 mm in layer 1, 9.3 mm in layer 2, 10.4 mm in layer 3 and 8.4 mm in layer 4 of Póckő . The mean size for the whole this locality is 8.5 mm. The mean size is also gradually increasing here at the higher part o f the section with the exception of layer 4, where the size is smaller again. This fact is related to the very high number of the small-sized species (P. a f f cerasulum, "Rhynchonella" triquetra, Terebratulida indet.).

From the most frequent taxa, such as C. plicatissima and P. aff. cerasulum, both small-sized juvenile and large-sized adult specimens can be found (see Figs 15-17).

COMPARISON W I T H THE E A R L Y JURASSIC F A U N A OF V Ö R Ö S H Í D Q U A R R Y (TARDOS, GERECSE MTS)

The brachiopods of several important Lower Jurassic sections from the Transdanu­bian Central Range were studied bed-by-bed during the last years (Lókút H i l l ; Som H i l l , Marko in the Bakony Mts and Vöröshíd quarry, Tardos in the Gerecse Mts). Unfortunate­ly determinable ammonites are missing from the basal layers of these sections, and the age of these sections were only constrained by ammonites from the younger layers. In the present case the comparison with the Vöröshíd quarry (see the location o f this locality on Fig. 1) w i l l give the most useful informations. The results of the study of the Vöröshíd quarry is not published yet, because the fauna o f some additional layers need to be col­lected. However, the examination of the collected fauna has already been done, therefore a comparison between the Vöröshíd quarry and the Lábatlan localities is possible.

A n approximately 14 m thick section was collected bed-by-bed above the unconfor­mity between the Triassic and Jurassic formations in the Vöröshíd quarry. This section can be divided into two parts based on the lithology and the distribution of the brachio­pods. There is 8 m of thick-bedded, reddish, slightly crinoidal limestone at the bottom of the Jurassic sequence. The lower 5 m of this limestone is shown on Fig. 12. Higher up a thinner-bedded, brownish-grey, micritic limestone can be found. Determinable am-

monites were found only in die upper part, which is Early Sinemurian (Semicostatum Zone) in age (PÁLFY, pers. comm).

The distribution of the brachiopod species within the figured section is shown on Fig 13. There are several brachiopod species at the Tölgyhát quarry and Póckő localities, which can also be found in the lower, thick-bedded layers of the Vöröshíd quarry. Ten species were determined in the lower 10 layers of the Vöröshíd quarry, of which 6 species are also known from the Lábatlan localities. Calcirhynchia plicatissima ranges through the sections at both area. Cuneirhynchia cartieri and Zeilleria mutabilis are pres­ent in all layers at the Lábatlan localities, but only at the thick-bedded layers at the V ö ­röshíd quarry. Liospiriferina alpina and Koninckodonta sp. are distributed in the lower part (up to layer 35) of the Vöröshíd quarry. "Rhync hone lia" triquetra can be found bet­ween layers 10 and 20 at the Vöröshíd quarry, in transitional position between the two different lithologies formations. Phymatothyris aff. cerasulum is very frequent at the Lá­batlan localities but occurs only in the upper part of the Vöröshíd quarry.

Hettangian Sinemurian Pliensbachian

Calcirhynchia plicatissima Calcirhynchia plicatissima

Calcirhynchia laevicosta Calcirhynchia laevicosta

Calcirhynchia fascicostata Calcirhynchia fascicostata

Salgirella albertii Salgirella albertii

Prionorhynchia cf. greppini Prionorhynchia cf. greppini

Cuneirhynchia cartieri Cuneirhynchia cartieri

Cuneirhynchia fraasi Cuneirhynchia fraasi

"Rhynchonella" triquetra "Rhynchonella" triquetra

Liospiriferina alpina Liospiriferina alpina

Liospiriferina aradasi

Liospiriferina guembeli

Lobothyris andleri Lobothyris andleri

Zeilleria mutabilis Zeilleria mutabilis

Zeilleria alpina Zeilleria alpina

Zeilleria choffati

Zeilleria cf. batilla

Fig. 14. Previously established stratigraphie ranges of the determined species of the Lábatlan localities

There are several brachiopod species in the upper, thin-bedded unit of the Vöröshíd quarry, which are absent at the Tölgyhát quarry and Póckő localities (e.g. Linguithyris aspasia, Apringia paolii, Pisirhynchia pisoides, Pisirhynchia retroplicata, Liospiriferina aequiglobata etc).

On the basis o f these facts, the examined layers of the Tölgyhát quarry and Póckő (the lower 3.5 m above the boundary between the Triassic and the Jurassic formations) can be correlated wi th the lower, thick-bedded part of the Vöröshíd quarry. Of course, in the absence of ammonites in both area, this correlation based on the distribution of the brachiopod species remains slightly uncertain.

A G E OF THE F A U N A

In the absence of ammonoids, the age of these layers can only be deduced from the distribution of brachiopods. Herein, the stratigraphie ranges of the examined brachiopod species is given on the basis o f A L M É R A S ( 1 9 6 4 ) fundamental work, but in some cases it is complemented with more recent Hungarian data from the Bakony Mts. ( V Ö R Ö S 1 9 8 3 « ,

D U L A I 1993/?) (Fig. 14) .

Fig. 15. Scatter diagram of relationship of width to length in Calcirhynchia plicatissima

Figs 16-17. Scatter diagram of relationships: 16 = width to length in Phymatothyris aff. cerasu­lum, 17 = thickness to width in Phymatothyris aff. cerasulum

Figure 14 clearly shows that practically all the occurring brachiopod species are known from Sinemurian formations, but there are several species, which are also charac­teristic elements o f the Hettangian faunas. Moreover, Liospiriferina guembeli is known only from the Hettangian. According to ALMÉRAS (1964), "Rhynchonella" triquetra is known from the Pliensbachian, but during the recent, detailed bed-by-bed collections, the range of several species was extended downwards, than it was known earlier.

On this basis, the lowest 3.5 m thick section of the Pisznice Limestone was probably deposited during the Late Hettangian and the Early Sinemurian. These results correspond wi th REZESSY'S (1996) examinations on cyclostratigraphy of the Pisznice Limestone. In his work three sections of the Gerecse Mts (Tölgyhát quarry, Bánya H i l l at Tardos and Kálvár ia H i l l at Tata) were correlated via their sedimentary cycles. The results of this study suggest, that Lower Jurassic sedimentation started earliest at the Kálvária H i l l , fo l ­lowed at the Tölgyhát quarry, and finally at the Bánya H i l l . Recent biostratigraphic study o f the Kálvária H i l l suggest a Middle Hettangian age of the basal layers of the Kálvária H i l l ( P Á L F Y , pers. comm). So the Late Hettangian - Early Sinemurian age o f the basal layers o f the Tölgyhát quarry confirms the cyclostratigraphic results.

According to REZESSY (1996), the 33.8 meter thick Upper Hettangian - Pliensba­chian section of the Tölgyhát quarry represents about 14 mil l ion years, so approximately 2.41 meter thick sediment was deposited during one mi l l ion years.

CONCLUSIONS

A detailed study of Early Jurassic brachiopod fauna of the eastern Gerecse has been done for the first time. A n efficient, bed-by-bed collection yielded a rich fauna (17 species) from the lowermost layers of the Pisznice Limestone at Lábatlan. On the basis of geological and paleontological similarity, the two localities (Tölgyhát quarry and Póckő) are discussed together.

The exact stratigraphical position of the Póckő specimens in the collection of the Hungarian Geological Institution is unknown but there are several differences between the old and the new collections (e.g. the absence of L . aspasia and the presence of P. aff. cerasulum in the new collection), hence the material of the Hungarian Geological Institu­tion was presumably collected, at least partly, from higher parts of the section. Thus only a taxonomic revision was made on this material, and only the recently collected material was considered further.

The recovery o f fossils from the Pisznice Limestone is very difficult, therefore there are lots of undeterminable fragments. However, the determinable specimens indicate a very diverse brachiopod fauna. For example, in layer 3 of Póckő the 10 determinable spe­cimens represent not less than 7 species. I t is peculiar in all layers that numerous species are present, but they are represented only by a relatively small number of specimens. Of course there are some exceptions, for example the number of P. aff. cerasulum speci­mens is remarkable high (24) in layer 4 of Póckő.

Regarding the taxonomic composition of the fauna, terebratulids are the predomi­nant group in nearly all layers. The only exception is layer 3 of Póckő, where the ratio of

rhynchonellids is about 75%. Spiriferids are entirely missing or play an insignificant role in the fauna.

The ratio o f disarticulated valves is very low at the lowermost layers of both lo­calities, but this ratio gradually increases in the higher layers of the sections. This i n ­crease is more significant at the Tölgyhát quarry, while less important at Póckő. The ratio of the sparitic infi l l ing of brachiopods is the highest in the lowest layers at both localities (more than 50%) and it decreases at the upper part of the sections. The average size o f brachiopods is smaller in the lower layers, and higher in the upper layers. The only ex­ception is layer 4 of Póckő, where the size decreases again. This is related to the very high number of P. aff. cerasulum, which is a very small-sized species.

The geological setting of the examined localities (significant distance from sea­mounts, basin-type sedimentation) as well as the low ratio of disarticulated valves (espe­cially in the lowest layers) indicate that transportation of brachiopods from a distant sea-mount is not very probable. Therefore the brachiopod fauna of these layers may represent the composition of an Early Jurassic deeper-water community (in contrast to the sections of Lókút H i l l and Vöröshíd quarry, which are in a basin-margin position and contain sev­eral redeposited specimens from the nearby seamounts). The size distribution of the most frequent species (Calcirhynchia plicatissima and Phymatothyris aff. cerasulum, Figs 15— 17) confirms this statement because they have both juvenile and adult specimens. I f transportation occurs, the specimens are usually sorted according to their sizes.

In the absence of ammonoids, the age o f this formation can be determined on the basis of the distribution of brachiopod species. Nearly all the occurring brachiopod species are known from the Sinemurian, but several species are also frequent in the Het­tangian faunas. Therefore the lowest 3.5 m thick section of the Pisznice Limestone at Lá­batlan was probably deposited during the Upper Hettangian and the Lower Sinemurian. These results agree with REZESSY'S (1996) conclusions based on cyclostratigraphy of the Pisznice Limestone.

Regarding the distribution of brachiopod species at the Lábatlan localities and at the Vöröshíd quarry, the examined Lábatlan sections can probably be correlated wi th the lower, thick-bedded part of the Vöröshíd quarry. O f course, in the absence of ammonoids in both area, the correlation is slightly uncertain.

There is no doubt about the Mediterranean character of the examined fauna. Of the six characteristic Mediterranean Sinemurian taxa, listed by V Ö R Ö S (1980, 1997) three are present at the Lábatlan localities (Linguithyris aspasia, Zeilleria venusta, Cuneirhynchia cartieri).

P A L E O N T O L O G I C A L NOTES

Cirpa latifrons (STUR in G E Y E R ) - There is only one specimen in the collection of the Hunga­rian Geological Institution. This species is known from Sinemurian localities of the Bakony Mts ( V Ö R Ö S 1997). C. latifrons was figured and described in detail from Lókút Hill by D U L A I (1992: 43) .

Cirpa cf. variabilis ( S C H L O T H E I M ) - Only one fragmentary specimen occurs in the collection of the Hungarian Geological Institution. C. variabilis is known from Sinemurian and Pliensbachian localities of the Transdanubian Central Range ( V Ö R Ö S 1997).

Calcirhynchia plicatissima (QUENSTEDT) - This is one of the most frequent species of these localities, found in all layers. C. plicatissima is well-known from Hettangian ( D U L A I 1993/;), Sine­murian and Lower Pliensbachian localities ( V Ö R Ö S 1997) of the Transdanubian Central Range. A wide range of sizes occurs from small-sized juvenile to large-sized adult specimens (Fig. 15), point­ing to a more or less autochthonous assemblage without significant transportation and size selec­tion. The outline of the juvenile specimens is more circular than that of the adult ones. This species was figured and described in detail (including the internal characters, on the basis of serial sections) from Hettangian and Early Sinemurian localities of the Bakony Mts ( D U L A I 1992: 44 and 1993b: 29).

Calcirhynchia cf. laevicosta (STUR in G E Y E R ) - Only one flat, fragmentary specimen occurs in the lowermost layer of Póckő. This species is also known from other Sinemurian localities in the Bakony and the Gerecse Mts ( V Ö R Ö S 1997).

Calcirhynchia fascicostata ( U H L I G ) - A small-sized juvenile specimen was found in layer 3 of Póckő and a larger adult one is present in the collection of the Hungarian Geological Institution. This species was mentioned from Pliensbachian localities of the Transdanubian Central Range ( V Ö R Ö S 1997).

Salgirella alberti (OPPEL) - Only one small-sized specimen was found in the lowermost layer of Póckő. This species occurs in the Hettangian Kardosrét Limestone ( D U L A I 1993b) as well as in the Upper Sinemurian of the Bakony Mts ( V Ö R Ö S 1997). The specimen is slightly flat, similar to G E Y E R ' s figured specimen (1889, Plate 5, Fig. 16). S. alberti was described in detail from Lókút Hill by D U L A I (1993/;: 30).

Prionorhynchia cf. greppini (OPPEL) - Several fragmentary specimens were found in the basal layers of Póckő. The planareas are not as well-developed as at other localities (for example at Lókút Hill , D U L A I 1992). The beak of the pedicular valve is erect, similar to GEYER'S figured spe­cimen (1889, Plate 6, Figs 5 and 7). A detailed description of P. greppini is given by D U L A I (1992: 47).

Prionorhynchia pseudopolyptycha ( B Ö C K H ) - A single, relatively small-sized specimen oc­curs in the collection of the Hungarian Geological Institution. This species, which was originally described by B ö C K H (1874) from the southern Bakony, is known from several localities of the Ba­kony and the Gerecse Mts in Hungary ( V Ö R Ö S 1997), but it has not been reported from other coun­tries. P. pseudopolyptycha was figured and described in detail from Lókút Hill by D U L A I (1992: 50).

Prionorhynchia sp. - Four fragmentary specimens were found at Póckő. The determination is based on the features of the shell and the ribbing.

Cuneirhynchia cartieri (OPPEL) - It is a common species at both examined localities. All spe­cimens are small or medium-sized and flat in appearance. The almost globular morphotype, which was found in the lower layers of the Lókút Hill in the Bakony Mts ( D U L A I 1990), is absent at Lá­batlan localities. C. cartieri is well-known from several Sinemurian localities of the Transdanubian Central Range ( V Ö R Ö S 1997). This species was figured and described in detail (including the inter­nal characters) from Lókút Hill by D U L A I (1992: 52).

Cuneirhynchia fraasi (OPPEL) - Some fragmentary specimens occur in layer 3 of Póckő and in the collection of the Hungarian Geological Institution. This species was reported from several Sinemurian localities of the Transdanubian Central Range (VÖRÖS 1997).

"Rhynchonella" triquetra G E M M E L L A R O - Some very small-sized specimens were found at the upper part of the Póckő locality. This species has never been mentioned from Hungary in the literature, but it was also found in the Vöröshíd quarry at Tardos. Serial sections were made on a Vöröshíd specimen, but the generic classification of this species is not solved yet. A L M É R A S (1964) mentioned "R". triquetra only from the Pliensbachian.

Liospiriferina alpina (OPPEL) - Several specimens occur at both localities. A significant part of Póckő specimens are not disintegrated, i.e. the two valves remained together during lbssilization, which is not very frequent at spiriferids, because of their hinge structure. This suggest a lack of sig­nificant transportation. L . alpina is a very common species in the Hungarian Liassic (Hettangian to

Annls iiist.-nul. Mus. natn. hung. 90, 199S

Pliensbachian) brachiopod faunas of the Transdanubian Central Range ( V Ö R Ö S in H A A S et al. 1984, V Ö R Ö S 1997). This species was figured and described in detail from Lókút Hill by D U L A I (1992: 55).

Liospiriferina aradasi ( G E M M E L L A R O ) - Only one specimen was found at the upper part of Póckő section. This species has never been mentioned from Hungary in the literature, but several specimens were also found at Borzavár in the Bakony Mts ( V Ö R Ö S , pers. comm). A L M É R A S (1964) mentioned this species from the Sinemurian.

Liospiriferina guembeli ( N E U M A Y R ) - One specimen is known from Póckő in the collection of the Hungarian Geological Institution and one other specimen from the first layer of Tölgyhál quarry. This species has never been mentioned from Hungary in the literature. The generic classifi­cation of this species follows ROUSSELLE (1977). There are several weak ribs and faint growth lines on the surface of the specimens, but they are smooth in appearance. According to A L M É R A S (1964), L . guembeli is known from the Hettangian.

Liospiriferina sp. - Small-sized, smooth specimens were found in layers 1 and 4 of Póckő. These are different from L . alpina in their more pointed beak, and the development of a weak uni-plication on the surface. Another two smooth spiriferid specimens, also in the collection of the Hungarian Geological Institution, arc different from L . alpina in their beak of the brachial valve, which is in very high position, nearly opposite to the beak of the pedicular valve.

Koninckodonta sp. - This taxon was found in the basal layer of Póckő, and in the collection of the Hungarian Geological Institution. The generic classification of the small-sized specimens is unambiguous on the basis of the characteristic shell structure and the concave brachial valve. How­ever, the poor preservation of the specimens makes a specific identification impossible.

Lobothyris andleri (OPPEL) - Three specimens occur in the upper part of Póckő section. All specimens are smaller in size, than it is known from the literature and from other localities (e.g. Hettangian Kardosrét Limestone, D U L A I 1993/?). They are probably juvenile specimens. This species is known from the Hettangian, Sinemurian and Pliensbachian localities of the Transdanu­bian Central Range ( D U L A I 1993/;, V Ö R Ö S 1997). L . andleri was figured and described in detail by D U L A I (1993/?: 37).

Linguithyris aspasia ( M E N E G H I N I ) - Only a small-sized, fragmentary specimen is known from the collection of the Hungarian Geological Institution. This species is one of the most frequent Late Sinemurian and Pliensbachian brachiopod of the Transdanubian Central Range ( V Ö R Ö S 1997) but recently it was also found in Early Sinemurian faunas by the author (Lókút Hill , Vöröshíd quarry). Specimens of L . aspasia are significantly smaller at all Lower Sinemurian localities, than it is known from younger formations. This species was figured and described from Lókút Hill by D U L A I

(1992: 67). Phymatothyris aff. cerasulum (ZlTTEL) - This taxon was found in both the Tölgyhát quarry

and Póckő section. In layer 4 of Póckő, this species is the predominant element of the fauna (more than half of the determinable specimens belong to this species). This taxon is clearly different from the typical P. cerasulum, because it is more flattened and more elongated than the Pliensbachian species (Figs 16-17). This form is also known from the upper part of the Vöröshíd quarry. P. cera­sulum was reported from Sinemurian and Pliensbachian localities of the Transdanubian Central Range ( V Ö R Ö S 1997).

Zeilleria cf. alpina (GEYER) - Relatively large-sized, but fragmentary specimens were found at the lower part of the Tölgyhát quarry and at the upper part of Póckő. Z. alpina is a common species in Sinemurian and Lower Pliensbachian formations of the Transdanubian Central Range ( V Ö R Ö S 1997). This species was figured and described in detail (including the internal characters) by D U L A I (1992: 71).

Zeilleria mutabilis (OPPEL) - This very variable species is known from both localities. At the basal layers of these localities small-sized, juvenile forms were found, which are pentagonal in out­line. More elongated specimens occur in the upper part of the Tölgyhát quarry and in the collection

of the Hungarian Geological Institution. This species is known from Hettangian, Sinemurian and Pliensbachian formations of the Transdanubian Central Range ( V Ö R Ö S 1997). Z. mutabilis was figured and described in detail (including the internal characters) by D U L A I (1992: 69 and 1993/?: 43 ) .

Zeilleria choffati ( H A A S ) - Several large-sized, elongated specimens were found at both lo­calities and in the collection of the Hungarian Geological Institution. This is the largest species known from the basal layers of the Pisznice Limestone. Z. choffati occurs at several Sinemurian lo­calities of the Transdanubian Central Range ( V Ö R Ö S 1997). This species was figured and described in detail (including the internal characters) by D U L A I (1992: 73) .

Zeilleria cf. batilla ( G E Y E R ) - Three fragmentary specimens occur in the upper part of the Tölgyhát quarry. This species has never been mentioned from Hungary in the literature, but several specimens were also found at Borzavár in the Bakony Mts (VÖRÖS, pers. comm). According to A L ­M É R A S (1964) , Z. batilla is known from the Sinemurian.

Zeilleria venusla ( U H L I G ) - Only a very small-sized juvenile specimen is known from the col­lection of the Hungarian Geological Institution. Apart from the size of the specimen (its length is 5.8 mm), all features are in good agreement with the well-known form of Z. venusta. This species is known from the Sinemurian localities of the Bakony Mts ( V Ö R Ö S 1997). A detailed description of Z. aff. venusla from Lókút was given by D U L A I (1992: 74) .

Zeilleria sp. - Two specimens occur in the collection of the Hungarian Geological Institution. Both forms are more elongated, than any other zeilleriids known from these localities.

Bakonyithyris sp. - Only a small-sized, fragmentary specimen is known from the collection of the Hungarian Geological Institution. This genus was described by V Ö R Ö S (1983/?) from Hungary and it is known from Sinemurian and Pliensbachian localities of the Transdanubian Central Range ( V Ö R Ö S 1997).

* * *

Acknowledgements - My sincere thanks are due to Dr. A T T I L A V Ö R Ö S who helped my work throughout with his advice. L Á S Z L Ó B E N K O V I C S , T E R É Z D U L A I , PÉTER GERNER and É V A ROSTA

helped in collecting the brachiopods at Póckő. Dr. L Á S Z L Ó KORDOS made the specimens haused in the collections of the Hungarian Geological Institution available for study. I thank Dr. JÓZSEF

P Á L F Y for his advice and reviewing the English text.

REFERENCES

ALMÉRAS, Y. (1964): Brachiopodes du Lias et du Dogger. - Dorum. Lab. GéoL, Fac. Sei., Lyon 5: 1-161. BöCKH, J. (1874): A Bakony déli részének földtani viszonyai. I I . (Die geologischen Verhältnisse des südlichen

Theiles des Bakony. II.) - Ann. Inst. Geol. Puhl. Hung. 3: I — 18t). D U L A I , A . (1990): The Lower Sinemurian (Jurassic) brachiopod fauna of the Lókút Hill (Bakony Mts.. Hun­

gary). Preliminary results. - Annls lust.-nat. Mus. natn. hung. 82: 25-37. D U L A I , A . (1992): The Early Sinemurian (Jurassic) brachiopod fauna ofthe Lókút Hill (Bakony Mts., Hungary).

- Fragtn. Min. et Pal. 15: 41-94. D U L A I , A . ( 1993«): Hettangian (Early Jurassic) megalauna and paleogeography of the Bakony Mts. (Hungary).

- In: PÁLFY, J. & VÖRÖS, A . (eds): Mesozoic Brachiopods of Alpine Europe. Hungarian Geological So­ciety, Budapest, pp. 31-37.

D U L A I , A . ( 1993/?): Hettangian (Early Jurassic) brachiopod fauna of the Bakony Mts. (Hungary). -- Fragm. Min. el Pal. 16: 27 50.

FÜLÖP, J. (1975): The Mesozoic basement horsl blocks of Tata. - Geol. Hung.. Ser. Geol. 16: 1-229.

GALÁCZ, A. & VÖRÖS, A. (1972): A bakony-hegységi jura fejlődéstörténeti vázlata a főbb üledékföldtani jelenségek kiértékelése alapján. (Jurassic history of the Bakony Mountains and interpretation of princi­pal lithological phenomena.) - Földi. Közi. 1 0 2 (2): 122-1 35.

GEYER, G . (1889): Über die liassischen Brachiopoden des Hierlatz bei Haistatt. - Abh. k. k. Geol. Reichsanst. 15: 1-88.

HAAS, J. (1988): Felsőtriász szelvények korrelációja a lofer-ciklusok alapján (Gerecse hegység). (Correlation of Upper Triassic profiles on the basis of Lofer cycles (Gerecse Mts).) - Földi. Közi. 117: 375-383.

HAAS, J., JOCHA-EDELÉNYI, F., GIDAI , L., KAISER, M., KRETZOI, M. & ORAVECZ, J. (1984): Geology of the

Sümeg area. - Geol. Hung.. Ser. Geol. 20 : 1-363. HOFMANN, K. (1884): Jelentés az 1883. év nyarán a Duna jobb partján Ó-Szőny és Piszke közt foganatosított

földtani részletes fölvételekről. (Bericht über die auf der rechten seile der Donau zwischen O-Szőny und Piszke im Sommer 1883 ausgeführten Geologischen Specialaufnahmen.) - Földt. Köz.l. 1 4 (4-8): 174-190,323-342.

KOCH, N. (1909): A tatai Kálváriadomb földtani viszonyai. (Die geologischen Verhältnisse des Kalvarienhügels von Tata.) - Földt. Köz.l. 39 (5): 255-275, 285-307.

KONDA, J. (1988): Gerecse, Lábatlan, Tölgyhát quarry. Geological Key Profiles of Hungary. - Hungarian Geo­logical Institution, Budapest, 6 pp.

KULCSÁR, K . (1914): A Gerecsehegység középső liászkorú képződményei. (Die mittel liassischen Bildungen des Gerecsegebirges.) - Földt. Köz.l. 44: 54-80, 150-175.

REZESSY, A. (1996): A Pisznicei Mészkő ciklussztratigráfiai vizsgálata gerecsei szelvényeken. [Cyclostrati-graphic evaluation of Pisznice Limestone on sections of the Gerecse Mts.] - Szakdolgozat, ELTE, Re­gionális Földtani Tanszék, Budapest, 84 pp. [Unpubl. manuscript.]

ROUSSELLE, L. (1977): Spiriférines du Lias moyen et supérieur au Maroc (Rides Prérifaines, Moyen Atlas) et en Espagne (Chaine Celtibérique orientale). - Notes Serv. géol. Maroc 38: 153-175.

VÉGH-NEUBRANDT, E. (1960): A Gerecse-hegység felső-triász képződményeinek üledékföldtani vizsgálata. (Pe-trologische Untersuchung der Obertrias-Bildungen des Gerecsegebirges in Ungarn.) - Geol. Hung., Ser.

' Geol. 12: 1-74. V Í G H , G . (1943): A Gerecse hegység északnyugati részének földtani és őslénytani viszonyai. (Die geologischen

und paläontologischen Verhältnisse im nordwestlichen Teil des Gerecse-Gebirges.) - Földt. Köz.l. 73 : 301-359,537-550.

VÍGH, G . (1961): A Gerecse-hegység nyugati felének földtani vázlata. (Esquisse géologique de la partie oc­cidentale de la Montagne Gerecse.) - Ann. Inst. Geol. Puhl. Hung. 4 9 (2): 445-462, 569-590.

VÖRÖS, A. (1980): Lower and Middle Jurassic brachiopod provinces in the Western Tethys. - Földi. Közi. 1 1 0 (3-4): 395-416.

VÖRÖS, A. (1983a): The Pliensbachian brachiopods of the Bakony Mts. (Hungary): a stratigraphical study. -Fragm. Min. et Pal. 11 : 29-39.

VÖRÖS, A. (19836): Some new genera of Brachiopoda from the Mediterranean Jurassic. - Annls hist.-nat. Mus. natn. hung. 75 : 5-25.

VÖRÖS, A. (1997): Magyarország jura brachiopodái. Faunafejlődés és paleobiogeográfia a Tethys nyugati ré­szén. (Jurassic brachiopods of Hungary.) - Hungarian Natural History Museum, Budapest, 1 10 pp.

VÖRÖS, A. & GALÁCZ, A. (1998): Jurassic paleogeography of the Transdanubian Central Range. - Riv. Ital. Pa-leant. 104(1) : 69-84.