Coniacian-Maastrichtian calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy in...

Newsletters on Stratigraphy Vol 472 (2014) 183ndash209 ArticleStuttgart June 2014

ConiacianndashMaastrichtian calcareous nannofossilbiostratigraphy and carbon-isotope stratigraphy in the Zagros Basin (Iran) consequences for thecorrelation of Late Cretaceous Stage Boundariesbetween the Tethyan and Boreal realms

Mohammad Javad Razmjooei1 Nicolas Thibault2 Anoshiravan Kani1 Azam Mahanipour3 Myriam Boussaha2 and Christoph Korte2

With 7 figures 2 plates and 1 table

Abstract Calcareous nannofossil biostratigraphy and stable isotope stratigraphy have been investigated inthe Shahneshin section of the Gurpi Formation from the Zagros Basin (Iran) The results show that the GurpiFormation spans the late early Coniacian to late Thanetian The age-model shows that the Shahneshin sectionspans the Coniacian to mid-Campanian with a good continuity whereas condensation is highlighted in thelate Campanian across the CampanianMaastrichtian boundary and in the late Maastrichtian Extreme con-densation is recorded after the Cretaceous-Paleogene boundary with the complete absence of the Danian andthe Selandian and lower Thanetian being comprised in only 6 m at the top of the Gurpi Formation Correla-tion of the carbon-isotope profile with other reference curves allows the recognition of several Late Creta-ceous excursions at the Shahneshin section such as the Beeding White Fall Kingsdown Michel Dean HavenBrow Horseshoe Bay Buckle Hawks Brow SantonianCampanian boundary (SCBE) and CampanianMaas-trichtian boundary (CMBE) events Correlation to a recently proposed global δ13C stack for the Late Creta-ceous points to a major mismatch of this compilation with magnetostratigraphy in the Santonianndashearly Cam-panian interval The δ13C correlation supported by calcareous nannofossil biostratigraphy brings insightsinto (1) the position of the ConiacianSantonian SantonianCampanian and CampanianMaastrichtianboundaries with respect to carbon-isotope stratigraphy and calcareous nannofossil bio-horizons and (2) theircorrelation between the Tethyan and Boreal realms

Key words Late Cretaceous calcareous nannofossil biostratigraphy carbon-isotope stratigraphy Zagros

copy 2014 Gebruumlder Borntraeger Stuttgart GermanyDOI 1011270078-042120140045

wwwborntraeger-cramerde0078-042120140045 $ 675

Authorsrsquo addresses1 Department of Geology Faculty of Earth Science Shahid Beheshti University Tehran Iran M J Razmjooei mjrazmjooeigmailcom2 Department of Geosciences and Natural Resource Management University of Copenhagen Oslashster Voldgade 10 DK-1350Copenhagen K Denmark N Thibault (corresp author present address) ntgeokudk3 Department of Geology Faculty of Science Shahid Bahonar University 22 Bahman Bolvar Kerman Iran

1 Introduction

The Cretaceous of Iran is characterised by a large di-versity of rocks and facies (Nabavi 1976) There are 27 different formations in the Mesozoic of the Zagrosarea 17 of those belong to the Cretaceous (Motiei1994) Sediments from the Cretaceous are well ex-posed in the Zagros basin southwest of Iran with anoverall good continuity and high sedimentation ratesFor a variety of reasons such as oil and gas reservoirsin Mesozoic and Cenozoic deposits numerous studieshave been focused on the formation of the basin (Mol-nar 2006 Talbot and Alavi 1996 Sepehr and Cosgrove2005) The Gurpi Formation which spans the LateCretaceous (SantonianndashMaastrichtian) to Paleocenein the west and southwestern part of the Zagros basinpredominantly consists of shales and marls (Stocklinand Setudehnia 1970) The Gurpi Formation is highlyfossiliferous and for this reason has been extensivelystudied for different biostratigraphical aspects Nu-

merous studies in the Zagros folded zone reveal sig-nificant lateral changes in the thickness age and litho-logical composition of the Gurpi Formation (Ghasemi-Nejad 2006 Hosseini 2006 Nabavi 2008 Asleshirin2011) The present study focuses on the Shahneshinsection of the Gurpi Formation in the west of the Za-gros Basin (Fig 1) The aim of the study is to establisha solid stratigraphic framework of the Shahneshin sec-tion based on calcareous nannofossils and bulk carbonstable isotopes and to provide correlations to other areas and oceanic basins spanning the same interval(Fig 2) The Late Cretaceous of this area remains apoorly known part of the Tethyan Realm and can im-prove the knowledge on calcareous nannofossil andstable isotope stratigraphy for the considered time in-terval which is mostly well-documented from Euro-pean and North American sections (Jenkyns et al1994 Jarvis et al 2002 2006 Sprovieri et al 2013Thibault et al 2012a Voigt et al 2010 2012) Strati-graphic correlations to other reference sections for this

M J Razmjooei et al184

Fig 1 Location and geological map of the studied area After the Geological map of Kazerun at 1100000

time interval are shown and address a number of issuesregarding global δ13C stratigraphy and the identifica-tion of Late Cretaceous stage boundaries

2 Geological setting

The Zagros basin is located in the western and south-western parts of Iran between the Arabian andEurasian lithospheric plates This structural zone iswidespread in nearby countries like Kuwait and Iraq(Takin 1972 Agard et al 2005) Numerous northwestsoutheast trending parallel folds were formed as a re-sult of the collision of Eurasia and Arabia during theCenozoic (Takin 1972 Agard et al 2005)

The Cretaceous deposits of the Zagros Basin gener-ally cover the Berriasian to Maastrichtian interval(Motiei 1994) Among these deposits the Gurpi For-mation investigated here is characterized by grey to blue marls and shales with occasionally intercalationsof thin beds of argillaceous limestones The thickness ofthe Gurpi Formation is changing significantly in differ-ent parts of the Zagros Basin (Motiei 1994) and this isprobably the result of the major Kazerum Fault and other north-south trending faults in the central part ofZagros (Sepehr and Cosgrove 2005) Based on fora -

minifera and calcareous nannofossil data the age of theGurpi formation has been shown to extend from lateSantonian to early Paleocene in some places (Asleshirin2011 in the Kuh-Sephid section Hadavi and Rasa Ezadi 2008 in the Dare-Shahr section) whereas onlyCampanian to Maastrichtian deposits are present in other areas of the Zagros Basin (Etemad et al 2008 inthe Kuh-Ghach section Sina et al 2010 in the Kuh-Soltan section) The Gurpi Formation was deposited ina deep shelf to basin margin setting during a majortransgressive phase (Bahrami and Parvanehnezhad Shi-razi 2010) Data from planktonic foraminifers (Abrari et al 2011 in the southwest of Firozabad Etemad et al2008 in Lar Area Hemmati-Nasab et al 2008 in theKaaver section Moradi 2010 in Farhad Abad section)benthic foraminifers (Hemmati-Nasab et al 2008Moradi 2010) palynology and sequence stratigraphicstudies (Rabani et al 2009 in the Dare Shahr section) indicate relatively deep basin conditions for the GurpiFormation in the studied area Ghasemi-Nejad et al(2006) suggest an open marine upper bathyal environ-ment for the deposition of the Gurpi Formation in theShahneshin section on the basis of palynofacies Hem-mati-Nasab et al (2008) suggested a rough estimationof 800 to 1200 m paleo-water depth for the Gurpi For-mation based on foraminifer plankticbenthic ratios

ConiacianndashMaastrichtian calcareous nannofossil biostratigraphy 185

Fig 2 Maastrichtian paleogeography with positions of several sections mentioned in the text (1) Shahneshin section Iran(2) Gubbio Italy (3) German chalk sections (4) English chalk sections (5) Olazagutia Spain (6) Waxahachie Dam Spill-way section Texas USA

The presence of various calcareous nannofossil and dinoflagellate cysts species with low latitude affinitiespoint toward deposition under subtropical latitudes forthe Gurpi Formation during the Late Cretaceous (Asle -shirin et al 2011 Hadavi et al 2007 Beiranvand et al2013) The studied section is situated on the southwest-ern flank of the Shahneshin anticline in the west of theFars province and in the north east of Kazerun city withthe first sample collected at the following coordinatesN 29deg 44 47 E 51deg 46 31 (Fig 1) The Coniacian-Maastrichtian interval of this section is ca 243 m thickwhich would point to an average sedimentation rate ofca 1 cmkyr but as shown further several condensed in-tervals can be identified so this value is under-estimated

3 Methods

31 Calcareous nannofossil assemblages

A total of 135 samples with a sampling resolution ofnearly 2 m were collected from the Shahneshin sectionand were processed using the gravity settling techniqueof Bown and Young (1998) This technique allows toconcentrate calcareous nannofossils in the slides by get-ting rid of much bigger and much finer particles Resultsobtained on absolute abundances (specimens per fieldof view) are not directly comparable to studies using asimple smear-slide technique However this techniqueis useful in biostratigraphy for the observation of rarespecies due to the absence of fine and big sedimentaryparticles that can potentially shroud the calcareous nan-nofossil assemblage The slides were prepared at thesedimentology laboratory of Shahid Beheshti Univer-sity and studied with a binocular microscope (EclipseE-600 pol) at 1000 magnification Calcareous nanno-fossil biostratigraphy and species richness were estab-lished based on presenceabsence of biostratigraphicmarkers and by examining an average of 100 fields ofview In addition the abundance of the different specieswas evaluated in 62 samples from the Cretaceous inter-val over a total of 300 specimens Key species are illus-trated in Plates 1 and 2 Bibliographic references for thecalcareous nannofossils are provided by Perch-Nielsen(1985) and Bown (1998) The CC biozonation of Sis -singh (1977) modified by Perch-Nielsen (1985) and theUCTP (Tethyan Province) of Burnett (1998) are appliedfor the Cretaceous of the investigated section (Fig 3)For the Paleogene the biozonation of Martini (1971)was applied The taxonomic concepts follow Perch-Nielsen (1985) and Bown (1998)


Fig 3 Calcareous nannofossil bio-horizons and biozona-tions used for the Cretaceous stratigraphy of the Gurpi For-mation in Shahneshin section based on Sissingh (1977)modified by Perch-Nielsen (1985) and Burnett (1998) Thenannofossil subzonation of Burnett (1998) corresponds tothe scheme for the Tethyan realm (TP)

32 Stable isotopes

Oxygen and carbon isotope composition of bulk rockswere measured on the same 135 samples analyzed forcalcareous nannofossils The analyses were carried outat the Department of Geosciences and Natural Re-source Management University of Copenhagen Den-mark using the Micromass Isoprime mass spectrome-ter The extraction of CO2 was executed by reactionwith anhydrous orthophosphoric acid at 70degC The analytical precision is measured at 015permil for oxygenand 008permil for carbon

33 Calcium carbonate content

135 samples were analysed for their CaCO3 contentThe CaCO3 content () was measured using the fol-lowing method bulk rock samples (02 g) were driedand homogenised and then dissolved with HCl (4 cc1 M) in a Bernard apparatus conical flask The CaCO3

content () was calculated using calibration to the relative pressure of carbon dioxide

4 Results

41 Sedimentological description of the Gurpi Formation

The type section of Gurpi Formation is located at thenorthwest of Zagros Basin on the southeastern plungeof Tang-e-Pabdeh north of the Lali Oil field inKhuzestan The succession consists of 320 meters ofgrey to blue marl and shale beds with occasional in-tercalations of thin beds of argillaceous limestone(James and Wynd 1965 Setudehnia 1972 Motiei1994) At the type section the Gurpi Formation over-lays the Ilam Formation disconformably as indicatedby paleontological data that suggest a 10 Myr hiatusbetween the two Formations (Wynd 1965) The GurpiFormation is overlain by the Pabdeh Formation con-formably at the type section (Motiei 1994)

In the Shahneshin section the Gurpi Formation con-sists of 2554 m of marl and marly limestone cycleswhich overlay limestones of the Ilam Formation withan apparent lithological discontinuity The basal con-tact of the Gurpi formation is marked in the studiedarea by an erosional surface which is associated withiron oxide nodules (Fig 4) The marly beds are grey toblack green and the marly limestone beds are lightgray to yellow and their thickness vary from a few centimeters to several meters The Gurpi Formation is

overlain by purple shales of the Pabdeh Formationwith an apparent concordant contact Subtle differ-ences in marls and marly limestones can be observedin the field and from the results from the CaCO3 con-tent (Fig 4) The definition of marls limy marls marl-limestone marly limestone and limestone relies on the Pettijohn et al (1975) classification based on theCaCO3 content as shown in Figure 4 The section canbe subdivided into 8 lithological units from the base to the top as defined on Figure 4

42 Calcareous nannofossil bio-horizonsand biozonations

The abundance of calcareous nannofossils varies be-tween 4 and 25 specimens per fields of view with anaverage of 12 The overall assemblage is dominated by Watznaueria barnesiae and W biporta Other abun-dant species are Cribrosphaerella ehrenbergii Rete-capsa angustiforata Micula staurophora and Predis-cosphaera cretacea Eiffelithus eximius and Trano-lithus orionatus are also quite abundant in the intervalbetween the base of the studied section and 164 m (topof zone CC21UC15c) reaching relative abundancesup to 17 and 8 respectively The preservation of thecalcareous nannofossils varies in the studied sectionfrom moderate to poor in the studied section based onvisual inspection of etching and overgrowth as de-scribed by Roth (1978) The species richness of Creta-ceous samples is quite low (varying between 18 and39) compared to typical Tethyan assemblages and thissuggests an important impact of diagenesis on the cal-careous nannofossil assemblage However most bio -stratigraphic markers of the studied interval have beenfound and show a consistent record with few sporadicoccurrences (Table 1 Plate 1 and 2) According to thedistribution of calcareous nannofossil biostratigraphicmarkers the Cretaceous part of the section spans zonesCC15 to CC26 of Sissingh (1977) and UC10 to UC20of Burnett (1998) The Paleocene part of the GurpiFormation includes zones NP5 NP7 and NP9 of Mar-tini (1971) and the base of the Pabdeh Formation iswithin NP9 (Fig 4 Table 1)

Results of the biostratigraphy suggest several strati-graphical gaps in the Late Cretaceous part of the GurpiFormation Also it was not always possible to retrieveall the different zones and subzones of Perch-Nielsen(1985) and Burnett (1998) schemes because of the absence of given stratigraphic markers or reversals in the supposed order of those markers (Fig 5) The po-sition of the ConiacianSantonian SantonianCampan-



Fig 4 Stratigraphy log and descriptionof the Shahneshin section The calcare-ous nannofossil UC subzonation of Bur-nett (1998) corresponds to the scheme forthe Tethyan realm (TP)

ian and CampanianMaastrichtian boundaries is notdetailed here and is rather discussed along with iso-topic results in chapter 53 The main bio-horizonsused for biozonation are highlighted in bold on Figs 56 and 7 to distinguish them from other bio-horizonsthat might have a regional significance These bio -stratigraphic results are based here on moderately topoorly preserved assemblages and the reliability of thestratigraphic position of bio-horizons in the Shah-neshin section should thus be considered with caution

The presence of Reinhardtites anthophorus in thefirst 19 m of the section attests of zone CC15 For theBurnett scheme the absence of Lithastrinus grillii inthe first 086 m of the section suggests the transitionfrom the top of UC10 to the base of UC11 The first occurrence (FO) of Lucianorhabdus cayeuxii recordedat 19 m marks the top of CC15 and UC11a-bTP Thesebiostratigraphic results thus suggest a Coniacian agefor the very base of the Gurpi Formation in the Shah-neshin section The FO of Hexalithus hexalithus is not-


Fig 5 Calcareous nannofossil biostratigraphy main calcareous nannofossil bio-horizons calcium carbonate content andbulk carbon and oxygen isotopic records of the Shahneshin section (1) The Cretaceous CC biozonation is that of Sissingh(1977) modified by Perch-Nielsen (1985) The UC biozonation is from Burnett (1998) and the subzonation corresponds tothe scheme for the Tethyan realm (TP) The low-pass filter of the δ13C curve shows 3 well-defined cycles in the Coniacianto lower Campanian interval Nannofossil bio-horizons used for the biozonations are in bold Secondary bio-horizons arealso shown for their potential use at the regional scale


Table 1 Distribution chart of calcareous nannofossil taxa in the Shahneshin section and inferred biozonations (upper part)



Table 1 Distribution chart of calcareous nannofossil taxa in the Shahneshin section and inferred biozonations (lower part)


ed at 115 m within CC15UC11a-b This species is asynonym of H gardetae whose FO is recorded withinUC12 in shelf sections of South England (Burnett1998) The FO of Calculites obscurus is recorded at208 m immediately after the FO of Lucianorhabduscayeuxii and marks the base of CC17 The resultingCC16 Zone is thus quite dense (only about 18 m) Thisbiozone is equivalent to part of UC11c (Fig 5) The FOof Broinsonia parca is recorded at 658 m and marksthe base of CC18 and UC14 Zone CC17 thus corre-sponds to zones UC11cTP to UC13 of the Burnettscheme The FO of A cymbiformis (1431 m) whichnormally defines the base of UC13 is recorded muchlater here (within CC21 and UC15cTP) than as proposedin the Burnett UC scheme Therefore the base of UC13cannot be defined here The FO of Bukryaster hayi co-incides with that of B parca constricta at 718 m andmarks the base of CC18b and UC14cTP Marthasteritesfurcatus has been observed in many samples oftenwith broken arms but shows sporadic occurrencesHowever it is continuously recorded toward the end ofits range and a last occurrence (LO) of this species canbe confidently placed at 774 m marking the base ofCC19 (Table 1) The FO of Ceratolithoides verbeekii at823 m marks the base of UC14dTP Misceomarginatuspleniporus was not found in any samples and for thisreason the top of UC14 is not clear The FO of Cera-tolithoides aculeus was found at 926 m and marks thebase of CC20 and UC15bTP The LO of Bukryaster hayiwhich normally marks the base of CC19b is hererecorded at 109 m above the FO of C aculeus thuswithin CC20 Uniplanarius sissinghii is rare and spo-radic but a FO can be recorded at 136 m and marks thebase of CC21 and UC15cTP

In the upper part of CC21UC15cTP lies the first occurrence of a characteristic ldquocurved spinerdquo nannolithwhich was already documented by Lees (2002) andshows a narrow range in the late Campanian of ODPHole 762C (Thibault et al 2012a) A similar narrowrange of this form is also documented here in the sameinterval and the FO of this curved spine form lies with-

in the uppermost part of CC21UC15cTP (Fig 5) Al-though this species has not been formally described it may prove useful as a potential new biostratigraphicmarker in the future The LO of Lithastrinus grillii isplaced at 1639 m but this species shows a very spo-radic signal before this level and thus the reliability ofthis bio-horizon is not very good here (Table 1) TheFO of Uniplanarius trifidus at 167 m marks the base ofCC22 and UC15d-eTP The LOs of Eiffellithus angus-tus (1811 m) Zeugrhabdotus diplogrammus (1765 m)and the curved spine (1784 m) are recorded withinCC22UC15d The LO of Reinhardtites anthophorus isrecorded here at 1474 m marking the end of a contin-uous consistent presence whereas the specimen record-ed at 1574 m is probably reworked (Table 1) The LOof Reinhardtites anthophorus is before the FO of U tri-fidus at 167 m in contradiction with Perch-Nielsenrsquosscheme Therefore it is not a reliable event for the baseof CC23 in this section The LO of Eiffellithus eximiusis difficult to place with certainty because of its incon-sistent occurrence toward the end of its range (Table 1)However this taxon is quite common up to 1639 m and shows a neat drop in abundance above this levelThe presence of this species then remains consistent upto 1709 m after which it is either absent or very rare(Table 1) This pattern is typical of the potential re-working of common species (Backman 1986 Raffi1999) Therefore the LO of E eximius is rather chosenhere at 1709 m According to Perch-Nielsen (1979)the LO of E eximius can be used as a secondary mark-er for the base of CC23 In addition this bio-horizonmarks the base of UC16 The bases of Zones CC23bUC17 CC24UC18 and CC25aUC19 are respectivelymarked by the LOs of Broinsonia parca constricta(2041 m) Tranolithus orionatus (2066 m) and Rein-hardtites levis (21215 m) The LO of Zeugrhabdotusbicrescenticus (2028 m) is observed within CC23UC16 One single specimen of Uniplanarius trifiduslong-rayed was found at 2084 m but it is probably re-worked given its absence in the preceding 5 samplesand the coincident LO of U trifidus short and medium-


Plate 1 Calcareous nannofossils of the Gurpi Formation in the Shahneshin section A ndash Eiffellithus eximius XPLB ndash Watznaueria barnesae XPL C ndash Tranolithus orionatus XPL D ndash Arkhangelskiella cymbiformis XPL E ndash Micula stau-rophora XPL F ndash Micula murus XPL G ndash Eiffellithus turriseiffelii XPL H ndash Broinsonia parca constricta XPL I ndash Cer-atolithoides aculeus XPL J ndash Eiffellithus angustus XPL as amended by Shamrock and Watkins (2009) K ndash Lucianorhab-dus cayeuxii XPL L ndash Ceratolithoides kamptneri XPL M ndash Reinhardtites levis XPL N ndash Reinhardtites anthophorus XPLO ndash Uniplanarius sissinghii XPL P ndash Uniplanarius trifidus XPL Q ndash Cruciplacolithus tenuis XPL R ndash Heliolithus klein-pellii XPL S ndash Micula prinsii XPL T ndash Curved spine XPL U ndash Discoaster multiradiatus PPL V ndash Discoaster mohleriPPL W ndash Fasciculithus tympaniformis XPL X ndash Biantholithus sparsus XPL



rayed at 1951 m (Table 1) The concomitant FOs ofLithraphidites quadratus Micula murus and Cerato -lithoides kamptneri that respectively mark the bases ofUC20aTP UC20bTP and UC20cTP at 2222 m suggest ahiatus in the late Maastrichtian of the Gurpi FormationIn the Perch-Nielsen scheme these subzones corre-spond to the interval CC25b to CC26a The FO of Mi -cula prinsii at 2428 m marks the base of UC20dTP andCC26b This last subzone is only 15 m thick suggest-ing that this interval is also condensed In the next sam-ple at 2443 m the concomitant presence of Crucipla-colithus tenuis Ellipsolithus macellus Biantholithussparsus and Fasciculithus tympaniformis mark zoneNP5 of Martini (1971) and thus highlight an importantgap across the CretaceousPaleogene transition of theGurpi Formation (Fig 5) These findings suggest thatthe Danian is completely absent here Moreover thetop of the section is also very condensed The FO ofDiscoaster mohleri marks the base of NP7 at 2473 mand the FO of Discoaster multiradiatus at 249 m attestsof NP9 These two zones belong to the Thanetian TheSelandian stage is thus solely represented by NP5 andcovers an interval of 3 m only From 249 m to the topof the section at 2569 m samples belong to zone NP9

43 Carbonate stable isotopes

431 Carbon isotopesThe long-term trend of the bulk carbonate δ13C of theShahneshin section shows a relative increase from val-ues ca 12 to ca 18permil from the base of the section inthe Coniacian to the SantonianCampanian boundary(Fig 5) In addition to this long-term trend the latterinterval is characterized by three main negative excur-sions each immediately followed by positive excur-sions (Fig 4) A number of identifiable minor positiveand negative excursions can also be observed in thisinterval of the Coniacian to late Campanian (Fig 4)Values remain relatively stable around 18permil up to themiddle of the late Campanian A stepwise negativeshift is observed at the transition between nannofossilzones UC15cTP and UC15d-eTP in the late Campanian

and values remain lower around 13permil up to zoneUC18 in the lower Maastrichtian The δ13C increasesagain sharply within zone UC18 and values remainstable upward at around 16permil up to the topmost partof zones UC20a-c A sharp decrease takes place fromthe upper part of UC20a-c and across the K-Pg bound-ary reaching the lightest values of ndash02permil in the firstsample of the Paleogene A very fast recovery of theδ13C is observed in the Paleogene reaching values of13permil at the top of the section within nannofossil zoneNP9 (Thanetian)

432 Oxygen isotopesThe bulk carbonate δ18O curve shows values fluctuat-ing around a stable average of ca ndash5permil from the baseof the section to the middle of zone UC15bTP in thelower Campanian A sharp increase is observed withinthe upper part of UC15bTP to reach values fluctuatingaround ndash45permil within UC15cTP Values increase againslightly up to ca ndash42permil within UC15d-eTP and reachminima around ndash41permil within zones UC16 to UC18 inthe early Maastrichtian The δ18O values fluctuatearound ndash44permil in zone UC20a-cTP and sharply de-crease within UC20dTP This latter decrease continuesacross the K-Pg boundary and reaches the lightest val-ues of ndash48permil in the Selandian and Thanetian (zonesNP5 and NP7) A sharp increase follows within NP9(Tha netian) reaching a value of ndash35permil in the last sam-ple of the section (Fig 5)

5 Discussion

51 Diagenetic overprint

The moderate to poor preservation of the calcareousnannofossil assemblage and the very low species rich-ness point to a potential diagenetic impact on primarygeochemical signatures However the range of vari-ability recorded in the measured carbon-isotopes cor-responds well to biogenic calcite precipitated in openand shelf oceans of the Late Cretaceous (Stoll and


Plate 2 Calcareous nannofossils of Gurpi Formation in the Shahneshin section A ndash Lithastrinus grillii XPL B ndash Zeug -rhabdotus embergeri XPL C ndash Marthasterites furcatus PPL D ndash Calculites ovalis XPL E ndash Rhagodiscus angustus XPLF ndash Lucianorhabdus maleformis XPL G ndash Tranolithus gabalus XPL H ndash Zeugrhabdotus bicrescenticus XPLI ndash Lithraphidites carniolensis XPL J ndash Cribrosphaerella ehrenbergii XPL K ndash Bukryaster hayi XPL L ndash Ceratolithoidesverbeekii XPL M ndash Micula praemurus XPL N ndash Ceratolithoides indiensis XPL O ndash Lithraphidites quadratus PPLP ndash Eiffelithus angustus rotated XPL as amended by Shamrock and Watkins (2009) Q ndash Watznaueria barnesae XPLR ndash Thoracosphaera operculata XPL S ndash Thoracosphaera sp 2 XPL T ndash Ellipsolithus macellus XPL

Schrag 2000 Jarvis et al 2006 Voigt et al 20102012) The general trends observed here match wellthose delineated in previous studies whereas absolutevalues are somewhat ca 1permil lower than coeval valuesin these studies (Jenkyns et al 1994 Jarvis et al 2006Voigt et al 2012 Sprovieri et al 2013 Wendler 2013)(Figs 6ndash7) This suggests that long-term trends in car-bonate δ13C are not profoundly affected by diagenesishere and that this geochemical proxy can be used forstratigraphy The lighter δ13C values at Shahneshinmay reflect either a slight diagenetic overprint or al-ternatively local conditions in the nannofossil speciescomposition and marine productivity Few diageneticoverprint of carbon isotope values is also supported bythe fact that the δ13Cndashδ18O cross-plot does not displayany correlation (R2 = 00008 Mitchell et al 1997)

Conversely the range of δ18O values (ndash35 tondash55permil) is relatively low compared to contemporane-ous diagenetically unaltered marine calcite of low latitude planktic foraminifers (Grossman 2012) Thismay indicate that the primary δ18O signal was over-printed by diagenetic fluids Therefore trends in bulkδ18O are not discussed further

52 Correlations to other Late Cretaceoussections

521 Correlation of carbon-isotopesDespite the influence of many potential local factors on the isotopic composition of carbon in carbonates ofepeiric shallow seas and pelagic oceanic basins greatsimilarities have been observed in the secular trends ofδ13C records This chemostratigraphic proxy is widelyused today for correlation at the global scale even between shelf and open ocean areas (Voigt et al 2010Wendler 2013 and references therein) Carbon isotopesrecords are thus used here for their application in strati -graphy and global correlations For further explanationson potential causes for δ13C fluctuations in the Late Cretaceous the reader is referred to Wendler (2013) andreferences therein Several studies have focused recent-ly on the global correlation of δ13C trends in numeroussections and deep-sea sites of the late CampanianndashMaastrichtian (Voigt et al 2010 2012 Thibault et al2012a 2012b Wendler 2013) Few studies have cov-ered the Coniacian to Campanian interval but a refer-ence curve was proposed for this interval based on theEnglish chalk (Jarvis et al 2006) These authors identi-fied and defined a number of isotopic events within thisinterval some of which can also be correlated to therecord of Seaford Head (Sussex Jenkyns et al 1994)

(Fig 6) From the Boreal TuronianConiacian boundarymarked by a pronounced δ13C minimum defined as theNavigation event (Fig 6) many characteristic positiveand negative excursions with different amplitudes andshapes have been defined by Jarvis et al (2006)throughout the Turonian to early Maastrichtian Most ofthese defined excursions from the Coniacian to earlyCampanian can actually be identified at Shahneshin andcorrelated to the English chalk (Fig 6) These excur-sions have also been previously identified and similarlycorrelated to the English chalk in the Laumlgerdorf recordof North Germany and in the Gubbio record which areused here for correlation (Fig 7) (Voigt et al 2010Sprovieri et al 2013) All together the long-term trendsof the Coniacian to early Campanian δ13C record is systematically characterized by three main cycles whichhave proved to constitute the expression of a 24 Myrlong-term eccentricity oscillation mode in the Earthrsquosclimate system (Sprovieri et al 2013) Following the pioneering work of Jarvis et al (2006) these δ13C ex-cursions as well as the Late Campanian negative event(LCE) and the CampanianMaastrichtian boundaryevent (CMBE) have been successfully used for the cor-relation of the English chalk with the German Chalk andthe Gubbio reference section in Italy (Voigt et al 2010Sprovieri et al 2013) The two latter studies present byfar the highest resolution δ13C records for the completeConiacianndashMaastrichtian interval and have thus beenchosen in the present study for correlation with theShahneshin section (Fig 7) Moreover the Gubbio sec-tions bear the reference magnetostratigraphic record forthe Late Cretaceous allowing a direct correlation to theGeologic Time Scale 2012 whereas the German andEnglish Chalk have an excellent macrofossil biozona-tion allowing a good tie to Boreal stage and substagedefinitions

Although the resolution of the δ13C curve of Shah-neshin is lower than the previous studies at Gubbio and in the German Chalk the comparison of the δ13Crecords shows a good correspondence in shapes andlong-term trends (Fig 7) In particular within the Coniacian-Santonian interval it is possible to identifyand correlate the Beeding White Fall KingsdownMichell Dean Haven Brow Horseshoe Bay BuckleHawks Brow and the SCBE events between Shah-neshin the English chalk the German chalk and Gub-bio (Figs 6ndash7) Moreover the extraction of long-termtrends of the Shahneshin record within this intervalthrough a low-pass filter delineates the 24 Myr cyclesin δ13C as also shown in Gubbio (Fig 7) (Sprovieri etal 2013) Finally the correlation of these isotopic



Fig

6

Cor

rela

tion

of th

e C

onia

cian

to e

arly

Cam

pani

an δ

13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

of th

e E

nglis

h ch

alk

(1)

A p

ossi

ble

re-

vise

d in

terp

reta

tion

of t

he m

agne

tost

ratig

raph

y of

Mon

tgom

ery

et a

l (1

998)

is

prop

osed

her

e fo

r th

e E

nglis

h ch

alk

base

d on

the

cor

rela

tion

of t

he S

CB

E t

o th

e G

ubbi

ore

cord


Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns

curves is further supported by comparable Tethyan cal-careous nannofossil bio-horizons between Shahneshinand the Gubbio area (Fig 7) The similar biostratigra-phies at Gubbio and Shaneshin make the tie of carbonisotopes very solid (Fig 7) Carbon isotopes were alsopreviously correlated between Gubbio and the Germanchalk by Sprovieri et al (2013) while Voigt et al (2010)correlated the German chalk to the English chalk Thecorrelation we present in Figure 5 between Shahneshinand the English chalk is thus a direct consequence ofthese past studies and of the tie between Shahneshinand Gubbio (Fig 7) This correlation suggests that it ishowever not possible to correlate calcareous nannofos-sil events between Iran and the English chalk (Fig 6)Therefore it is here suggested that a few common cal-careous nannofossil bio-horizons are time-transgres-sive between the Tethyan and Boreal realms in the Santonian-Campanian interval (Fig 6) The LCE couldnot be identified in the Shahneshin section In additionimmediately after the FO of U trifidus which can becorrelated between Shahneshin and Gubbio the δ13Cpatterns at Shahneshin are characteristic of the largenegative CMBE Therefore our correlation suggestsanother important hiatus in the Shahneshin section at165 m within the top of UC15cTP corresponding to theoverall interval between the base of the LCE and thebase of CMBE expressed at Gubbio and in the Germanchalk (Fig 7) This means that a large part of the lateCampanian is missing at Shahneshin as also supportedby the condensation of zone CC22UC15d-eTP (Fig 7)The CMBE can be correlated between the three recordsand several similar calcareous nannofossil bio-hori-zons are recorded in the three sections within the upperhalf of the excursion immediately before or within therecovery to more positive values (Fig 7) Condensationof the Maastrichtian interval at Shahneshin preventsany further correlation of the δ13C curve with other ref-erence records in the upper part of the MaastrichtianFinally the negative excursion observed across theK-Pg boundary and the very rapid positive recovery isin accordance with the timing of global δ13C recordsand with the condensation identified from the bio -stratigraphy in the Paleogene of the Shahneshin sectionGlobal δ13C values of the Danian and early Selandianremain relatively low after the major K-Pg negative excursion and the full recovery toward more positivevalues is only observed in the interval between the lateSelandian and early Thanetian (Cramer et al 2009)Therefore the extremely sharp positive peak observedafter the K-Pg boundary in the δ13C of the Shahneshinsection (Fig 7) is in agreement with a Thanetian age

and reflects the extreme condensation of the Paleogenein the Gurpi and Pabdeh Formations

53 Implications for the definition and correlation of Late Cretaceousstage boundaries between the Boreal and Tethyan Realms

Following the first international symposium on Creta-ceous stage boundaries in Copenhagen in 1983 LateCretaceous stage boundaries have been quite well de-fined in the Boreal Realm based on the correlation ofmany European sections and proposals of several bio-horizons have been made to correlate to the Tropicalrealm (Birkelund et al 1984) However the provin-ciality observed in many fossil groups makes the cor-relation between the Boreal Realm the Western Inte-rior the Tethys and deep-sea sites of the South At-lantic Pacific and Indian Oceans a difficult exerciseThe results of the Shahneshin section and correlationto Gubbio (Italy) and to the German and English Chalkhave implications on the definition and correlation ofLate Cretaceous stage boundaries with respect to cal-careous nannofossil biostratigraphy and carbon-iso-tope stratigraphy

531 Age-model for the Shahneshin sectionThe calcareous nannofossil biostratigraphy and thepreceding isotopic correlations suggest that the GurpiFormation presents a number of gaps and condensedintervals throughout the ConiacianndashPaleogene at theShahneshin section The base of the Shahneshin sec-tion corresponds to the lower Coniacian UC10 biozone(Fig 5) Underneath the base of the Coniacian is miss-ing and an unconformity between the Turonian and the upper lower Coniacian is marked by the transitionbetween the Ilam and Gurpi Formations Three otherhiati have been characterized in the late CampanianCC22UC15d-eTP zone in the Maastrichtian at theUC19UC20 transition and at the K-Pg boundaryabove which the whole Danian and most of the Se-landian and Thanetian are missing This extreme con-densation is supported by the results on stable isotopesand it demonstrates that the first 85 Myr of the Paleo-gene are actually comprised in ca 6 m in the top partof the Gurpi Formation In addition the upper Maas-trichtian is very condensed as attested by the absenceof the characteristic δ13C excursions of this intervaland the limited thickness of UC20dTP However theupper lower Coniacian to lower Campanian intervalseems rather continuous and the correlation of the


calcareous nannofossil bio stratigraphy and isotopictrends with Gubbio and the German chalk has impor-tant implications for the ConiacianSantonian and San-tonianCampanian boundaries which have not yet beenratified by the International Commission on Stratigra-phy (ICS)

532 Definition and correlation of the ConiacianSantonian boundary of the Tethyan and Boreal Realms

In the Tethyan realm the first appearance of the am-monite subgenus Texanites was originally consideredas a good indicator for the base of the Santonian(Kennedy 1984) This bio-horizon has been rejected bythe Santonian Working Group and the favored primarymarker is currently the first appearance of Cladocera-mus undulatoplicatus (Inoceramid) which is easily rec-ognizable and widespread (It is known from N Amer-ica Europe Africa Madagascar and Central AsiaLamolda et al 1996) The first appearance of thisspecies defines the base of the pachtiundulatoplicatusmacrofossil zone in the German Chalk (pu on Fig 7)and is recorded at the level of the Michel Dean Flint inthe English chalk immediately below the Michel Deanevent within the Micraster coranguinum zone (Fig 6)(Mortimore et al 2001 Paul and Lamolda 2009) Sofar the coincidence between the FO of C undulatopli-catus and the Michel Dean δ13C event has been shownat Olazagutia (Spain) Ten Mile Creek (Texas) CulverCliff Trunch and Dover (England) and Laumlgerdorf(Germany) (Paul and Lamolda 2009 Voigt et al 2010)The Michel Dean event is thus chosen for placement ofthe ConiacianSantonian boundary in the Shahneshinsection (Figs 6ndash7) The FOs of calcareous nannofossilsC obscurus and L cayeuxii conformably lie slightlybelow the Kingsdown event at Gubbio and Shahneshinand hence seem to constitute reliable markers for thebase of the Santonian in the Tethyan province (Fig 7)The FOs of the two latter taxa are also recorded in thesame stratigraphic order slightly below the ConiacianSantonian boundary in the Olazagutia section Spain(Lamolda and Paul 2007) and in the RomanianCarpathians (Melinte and Lamolda 2007) The FO ofC obscurus is recorded within the Micraster coran-guinum zone ca 18 m below the Michel Dean Flint atSeaford Head (Sussex English chalk Hampton et al2007) Assuming similar sedimentation rates along thesouthwestern coast of England this level projects ap-proximately between the Kingsdown and White Fallevents on the TrunchDover carbon isotope profile(Fig 6) This projection is also supported by a good

correspondence of facies between the two records theHope Point Marls and Otty Bottom marls of Dover(Jarvis et al 2006) representing the equivalent of theBelle Tout Marls at Seaford Head (Hampton et al2007) whereas the prominent East Cliff SemitabularFlint of Dover likely represents the equivalent of theSeven Sisters Flint at Seaford Head Therefore the level of the FO of C obscurus at Seaford Head wouldlie slightly below the Kingsdown event as defined inDover (Fig 6) conformably to the Tethyan record Inthe Trunch borehole the FO of C obscurus was record-ed much further up in the stratigraphy in coincidencewith the SCBE (Jarvis et al 2002) Interestingly thislevel corresponds well to the first occurrence of an in-flux in C obscurus at Seaford Head (Fig 6 Hampton etal 2007) It is possible that the apparent FO of C ob-scurus in the Trunch borehole actually marks the sameinflux event as at Seaford Head and is caused by the extreme scarcity of this marker below this level Theuse of the FO of C obscurus as a calcareous nannofos-sil marker for the ConiacianSantonian boundary maythus be somewhat reliable between the Tethyan and Boreal realms but it must be used with caution in theBoreal realm due to its sporadic occurrence close to the base of its range (Hampton et al 2007) The posi-tion of the ConiacianSantonian at Shahneshin usingthe Michel Dean event for correlation with the Borealrealm lies in the lower half of calcareous nannofossilzone CC17 (UC11cTPndashUC13) (Figs 6ndash7)

533 Definition and correlation of the SantonianCampanian boundary of the Tethyan and Boreal Realms

Currently the favored boundary criterion chosen bythe Campanian Working Group for the base of theCampanian is the extinction level of the crinoid Mar-supites testudinarius which also marks the LO of thewhole Marsupites genus (Gale et al 2008) Amongother criteria proposed for the base of the Campanianare the FO of calcareous nannofossil Broinsonia par-ca parca which also marks the FO of the whole Broin-sonia parca lineage the LO of planktonic foraminiferDicarinella asymetrica and the C33RC34N paleo-magnetic reversal (Montgomery et al 1998 Gale et al 2008) The level of extinction of M testudinariusdefines the top of the testudinariusgranulata zone inthe German chalk (tsgr on Fig 7) and is thus directlycorrelatable to the English chalk coinciding in bothrecords to the base of δ13C event SCBE (Voigt et al2010) (Figs 6ndash7) The FO of B parca parca lies abovethat level within zone Offaster pilula in the English


chalk (Fig 6) The C33RC34N reversal as interpretedby Montgomery et al (1998) in the English chalk cor-responds to the Buckle Marls at Seaford Head and iswithin the Uintacrinus socialis zone (Us on Fig 6)well below the extinction of M testudinarius Actual-ly the C33RC34N reversal is just above the Horse-shoe Bay event and nearly in coincidence with theBuckle event (Fig 6) The C33RC34N reversal atGubbio lies in-between the Buckle and Horseshoe Bayevents which is reasonably similar to the English chalkinterpretation (Fig 7) This level at Gubbio is also co-incident with the LO of planktonic foraminifer D asy-metrica and with the FO of calcareous nannofossilB parca parca (Fig 7) The good match in the corre-lation of carbon isotopes and main nannofossil bio-horizons in the Coniacian to lower Campanian intervalbetween Gubbio and Shahneshin and the correlation to the English chalk (Figs 6ndash7) allows us to draw thefollowing conclusions with respect to the position ofthe SantonianCampanian boundary

(1) The base of the Campanian as defined by the ex-tinction of Marsupites testudinarius corresponds to theso-called SCBE carbon isotope event and lies withinChron C33R in the English chalk (Boreal realm) Thislevel corresponds to the very top of Chron C33R atGubbio (Tethyan realm) close to the C33NC33R re-versal Based on the comparison with Gubbio and onthe occurrence of many additional zones of normal po-larity within macrofossil zones O pilula and G qua d-rata (Fig 6) a possible revised interpretation of themagnetostratigraphic Montgomery record could pointto a large part of the lower Campanian of the Englishchalk actually corresponding to chron C33N (Fig 6)

(2) The base of the Campanian as defined by the coin-cident C34NC33R reversal and by the LO of plankton-ic foraminifer D asymetrica lies in-between the Horse-shoe Bay and Buckle carbon isotope events at Gubbio(Fig 7) and thus corresponds in the English chalk to thebase of the Uintacrinus socialis zone (Fig 6)

(3) The FO of B parca parca appears to be time-transgressive between the Tethyan (Shahneshin andGubbio) and the Boreal realm (English and Germanchalk) In the Boreal realm it lies well above theSCBE (Fig 6) whereas in the Tethyan realm it lies in-between the Horseshoe Bay and Buckle carbon isotopeevents in coincidence with the FO of D asymetricaand the C34NC33R reversal (Fig 7)

(4) Consequently some of the criteria chosen by theCampanian Working Group for the definition of the

base of the Campanian appear to be diachronous Sincethe favored marker is the LO of M testudinarius theBoreal definition should be adopted corresponding tothe SCBE However this implies that at least in someparts of the Tethyan Realm this level is actually closeto the C33NC33R reversal as observed in Gubbio(Fig 7) This stratigraphic level would also be muchbetter defined by the FO of the calcareous nannofossilCeratolithoides aculeus as suggested by our correlationbetween Gubbio and Shahneshin (Fig 7)

To confirm these results and resolve the problematiccorrelation of the SantonianCampanian boundary be-tween North America Europe and southern Tethyansites more work is needed on potential boundary stra-totype sections such as the currently favored Waxa-hachie Dam Spillway section (Texas) (Gale et al2008) but also on other potential sections such as in the Hateg area Romania (Melinte-Dobrinescu and Bojar 2010) To resolve this issue it may be necessaryto study the boundary in a much broader context toperform very high-resolution carbon isotope analysisin addition to the biostratigraphy in order to retrievewith precision the numerous events of Jarvis et al(2006) It appears necessary to find sections wherelarge parts of the Coniacian and lower Campanian arealso exposed in order to document the 24 Myr cyclesof Sprovieri et al (2013) In particular the two24 Myr δ13C cycles with maxima at the HorseshoeBay event and SCBE have quite similar amplitudes atShahneshin in the German chalk and in the Englishchalk and can be easily misidentified if not studied ina broad context (Figs 6ndash7)

According to Burnett (1998) the SantonianCam-panian boundary would lie somewhere within nanno-fossil zone CC17UC11cTPndashUC13 below the FO ofB parca parca Our results and correlations suggestthat this boundary level as defined by the LO ofM testudinarius in the English and German chalkwould actually correspond in the Tethyan realm to thebase of CC20UC15bTP

534 Definition and correlation of the CampanianMaastrichtian boundaryof the Tethyan and Boreal Realms

The CampanianMaastrichtian boundary (CMB) isnow very well defined globally and tied to the firstminimum in δ13C values of the CMBE preceding theso-called event M1+ (Thibault et al 2012a 2012bVoigt et al 2012) This level projects approximately at195 m at Shahneshin within zone CC23 (UC16) with-


in CC2223 (UC16) at Gubbio and in the top of UC16in the German chalk (Fig 7) The last occurrence ofUniplanarius trifidus is the first bio-horizon lying im-mediately above the CampanianMaastrichtian bound-ary at Shahneshin and Gubbio In the German chalkthe LO of a form defined as U cf U trifidus is alsofound above this boundary at the base of δ13C eventM1+ similarly to the Gubbio record (Fig 7) Unipla-narius trifidus is a very characteristic tropical nanno-lith unlike any other calcareous nannofossil species ofthis time interval Although this species is quite rareandor generally absent in the Boreal realm it is verylikely that U cf U trifidus identified in Germany byBurnett in Schoumlnfeld et al (1996) is actually a trueU trifidus The LO of U trifidus is one of the rare re-liable Maastrichtian calcareous nannofossil strati-graphic markers in the Indian Ocean ODP Site 762Cand it was also found there immediately above theCMB (200 kyr after the identified CMB level Thi-bault et al 2012b) Consequently the LO of U trifidusappears to be an excellent nannofossil marker for theCampanianMaastrichtian boundary and should beconsidered in future revised nannofossil biozonations

535 Position of substage boundaries at Shahneshin

The lowerupper subdivision of the Campanian used inthe Tethyan scheme of Burnett (1998) projects corre-sponds to the FO of Uniplanarius sissinghii Unipla-narius sissinghii is rare and sporadic at Shahneshin but its FO can be placed at 136 m marking the base ofCC21 and UC15cTP According to the Burnett schemethis level corresponds to the base of the belemniteBelemnitella mucronata zone in Northwest Europe andthis level projects slightly below the ldquolowermiddlerdquoCampanian boundary in North American usage as defined by the first occurrence of ammonite Baculitesobtusus (Ogg et al 2012) In the German chalk thislevel corresponds to the base of the conicasenior zone(Voigt et al 2010) (Fig 7) The lowerupper Maas-trichtian boundary may be placed here at the FO ofLithraphidites quadratus (Fig 7) following Thibault etal (2012a 2012b)

54 Implications for the global Late Cretaceous δ13C stack and the Geologic Time Scale

Wendler (2013) recently proposed a global averageδ13C stack for the Turonian through Maastrichtianbased on a very large literature compilation This stack

was presented against the magnetostratigraphy the for-mer Geologic Time Scale (GTS 2004 Gradstein et al2004) and the most recent one (GTS 2012 Ogg et al2012) This stack was redrawn here based on ages fromthe GTS 2012 and compared to δ13C records and strati-graphic data of Shahneshin Gubbio and the Germanchalk (Fig 7) The comparison of Coniacian to lowerCampanian stage and substage boundaries as defined inthe Boreal realm and of δ13C correlations of the eventsdefined by Jarvis et al (2006) between Gubbio NorthGermany and the Wendler compilation delineates a ma-jor mismatch of this stacked curve with the magne-tostratigraphy of this interval (Fig 7) In particular asshown at Gubbio the negative excursion following theHorseshoe Bay event marks the C33rC34n reversaland the SCBE occurs exactly at the C33nC33r rever-sal In contrast the Wendler compilation places theSCBE at the C33rC34n reversal i e ca 4 Myr earlierthan suggested by the Gubbio record This mismatchhas a very strong impact on the respective duration es-timations of the Santonian and Campanian stages andtherefore needs to be addressed thoroughly for the next generation of Cretaceous Geologic Time ScalesSprovieri et al (2013) showed that the long-term δ13C trends across the Coniacian to Santonian intervalactually correspond to three well-pronounced 24 Myrlong-term eccentricity cycles (Fig 6) The expressionof these three 24 Myr cycles is a remarkable commonfeature of Shahneshin Gubbio and the German chalk(Fig 7) Therefore using either the age of the C33nC33r reversal or that of C33rC34n as potential an-chors as well as the cyclostratigraphic frame of Spro -vieri et al (2013) for the high-resolution carbon isotopecurve of Gubbio it should be possible to correct theLate Cretaceous Wendler δ13C stack which will provevery useful for future geologic time scales

6 Conclusions

The calcareous nannofossil biostratigraphy and stableisotope stratigraphy of the Shahneshin section alloweddrawing the following conclusions

(1) The Gurpi Formation in the western part of the Zagros Basin spans the Coniacian to Thanetian

(2) Calcareous nannofossil bio-horizons and carbon-isotope stratigraphy at Shahneshin suggest condensa-tion in the late Campanian and in the lower part of thelate Maastrichtian a gap corresponding to the entireDanian stage and a major condensation of the Paleo -


cene with ca 85 Myr comprised in only 6 m at the topof the Gurpi Formation

(3) Correlation of the carbon-isotope profile with other reference records has allowed the identificationof the following Late Cretaceous excursions at Shah-neshin the Beeding White Fall Kingsdown MichellDean Haven Brow Horseshoe Bay Buckle andHawks Brow events as well as the SCBE and CMBE

(4) The FO of Calculites obscurus which marks the base of zone CC17 of the Perch-Nielsen (1985)scheme occurs nearly in coincidence with the positiveKingsdown δ13C event at Shahneshin and GubbioThis bio-horizon is situated below the ConiacianSan-tonian boundary as defined in the English chalk by theFO of Inoceramid Cladoceramus undulatoplicatusand coincident to the Michel Dean δ13C event

(5) The FO of Broinsonia parca parca is recorded in-between the Horseshoe bay and Buckle δ13C eventsat Shahneshin which correlates well with the Gubbiorecord Correlation of the Tethyan Shahneshin andGubbio sections to the German and English chalk (Bo-real realm) suggests that this bio-horizon is time-trans-gressive between the two provinces and is thus not re-liable as a global marker for the SantonianCampanianboundary

(6) The SantonianCampanian boundary as definedby the LO of Marsupites testudinarius corresponds tothe δ13C SCBE In the English chalk (Boreal realm)this stratigraphic level lies below the FO of B parcaparca in subzone UC13iiiBP At Shahneshin and Gub-bio (Tethyan realm) this level actually corresponds tothe FO of Ceratolithoides aculeus which defines thebase of CC20UC15bTP UC Boreal and Tethyan nan-nofossil zones are not analogous in this interval

(7) Correlation of δ13C records with the global stackof Wendler (2013) highlights a mismatch of this com-piled record to magnetostratigraphy and the GeologicTime Scale in the Santonian and lower CampanianThis is mainly due to the position of the SCBE that isnot coincident with the C33RC34N reversal As sug-gested by the Gubbio record and a proposed reinter-pretation of the English chalk magnetostratigraphy the SCBE rather coincides with the top of C33R andpossibly with the C33NC33R reversal

Acknowledgements We are grateful to B Salehipour(GeoPardazesh Petroleum Exploration Company Iran) forhis help during the sampling in the field Geochemicalanalyses received support from the Carlsberg foundation

Denmark We thank Bo Petersen (Univ Copenhagen) forsupport in the MS lab We thank Silke Voigt and an anony-mous reviewer for their constructive and helpful commentsand suggestions

References

Abrari N Vaziri-Moghaddam H Taheri A Seirafian A2011 Biostratigraphy and Palaeobathymetry of GurpiFormation in south west of Firozabad Iranian Journal ofGeology 7 49ndash60

Agard P Omrani J Jolivet L Mouthereau F 2005Convergence history across Zagros Iran constraintsfrom collisional and earlier deformation InternationalJournal of Earth Sciences 94 401ndash419

Asleshirin F 2011 Nannostratigraphy of Gurpi Formationin Kuh-e sephid section (eastern of Ramhormoz) Masterthesis Faculty of earth science Shahid beheshti Univer-sity 178 pp

Backman J 1986 Accumulation patterns of Tertiary cal-careous nannofossils around extinctions GeologischeRundschau 75 185ndash196

Bahrami M Parvanehnezhad Shirazi M 2010 Microfa-cies and sedimentary environments of Gurpi and PabdehFormations and the type of MesozoicndashCenozoic bound-ary in Fars province Iran Journal of Applied Geology 5330ndash335

Barrera E Savin S M 1999 Evolution of late Campan-ianndashMaastrichtian marine climates and oceans In Bar-rera E Johnson C C (Eds) Evolution of the Creta-ceous Ocean-Climate System Geological Society ofAmerica Special Paper 332 245ndash282

Batenburg S J Sprovieri M Gale A S Hilgen F JHuumlsing S Laskar J Liebrand D Lirer F Orue-Etxe-barria X Pelosi N Smit J 2012 Cyclostratigraphyand astronomical tuning of the Late Maastrichtian at Zu-maia (Basque country Northern Spain) Earth and Plane-tary Science Letters 359ndash360 264ndash278

Beiranvand B Ghasemi-Nejad E Kamali M R 2013Palynomorphsrsquo response to sea-level fluctuations a casestudy from Late CretaceousndashPaleocene Gurpi Forma-tion SW Iran Journal of Geopersia 3 11ndash24

Birkelund T Hancock J M Hart M B Rawson P RRemane J Robaszynski E Schmid R Surlyk F1984 Cretaceous stage boundaries ndash Proposals Bulletinof the Geological Society of Denmark 33(1ndash2) 3ndash20

Bown P R (Ed) 1998 Calcareous Nannofossil Biostratig-raphy British Micropaleontology Society Publication Se-ries Chapman and HallKluwer Academic London317 pp

Bown P R Young J R 1998 Techniques In Bown P R(Ed) Calcareous Nannofossil Biostratigraphy BritishMicropaleontology Society Publication Series Chapmanand HallKluwer Academic London pp 16ndash28

Burnett J A 1998 Upper Cretaceous In Bown P R(Ed) Calcareous Nannofossil Biostratigraphy British


Micropaleontology Society Publication Series Chapmanand HallKluwer Academic London p 132ndash199

Clarke L J Jenkyns H C 1999 New oxygen isotope evidence for long-term Cretaceous climatic change in theSouthern Hemisphere Geology 27 699ndash702

Cogneacute J P Humler E 2004 Temporal variations ofoceanic spreading and crustal production rates during thelast 180 My Earth and Planetary Science Letters 227 39ndash427

Cramer B S Toggweiler J R Wright J D Katz M EMiller K G 2009 Ocean overturning since the LateCretaceous Inferences from a new benthic foraminiferalisotope compilation Paleoceanography 24 doi1010292008PA001683

Etemad M Vaziri-Moghadam H Amiri Bakhtiar HRahmani A 2008 Biostratigraphy and Bathymetry ofthe Gurpi Formation in Lar Area (Kuh-e-Gach) Based onPlanktonic Foraminifera Esfahan University ResearchJournal (Science) 1 57ndash68

Gale A S Hancock J M Kennedy W J Petrizzo M RLees J A Walaszczyk I Wray D S 2008 An inte-grated study (geochemistry stable oxygen and carbonisotopes nannofossils planktonic foraminifera inoce-ramid bivalves ammonites and crinoids) of the Waxa-hachie Dam Spillway section north Texas a possibleboundary stratotype for the base of the Campanian StageCretaceous Research 29 131ndash167

Gardin S Galbrun B Thibault N Coccioni R Premoli-Silva I 2012 Bio-magnetochronology for the upperCampanian ndash Maastrichtian from the Gubbio area Italynew results from the Contessa Highway and Bottaccionesections Newsletters on Stratigraphy 45 75ndash103

Ghasemi-Nejad E Hobbi M H Schioslashler P 2006 Di-noflagellate and foraminiferal biostratigraphy of theGurpi Formation (upper Santonian ndash upper Maastricht-ian) Zagros Mountains Iran Cretaceous research 27828ndash835

Gradstein F M Ogg J G Smith A G (Eds) 2004 A Geologic Time Scale 2004 New York Cambridge UKCambridge University Press 599 pp

Grossman E L 2012 Chapter 10 ndash Oxygen IsotopeStratigraphy In Gradstein et al (Eds) The GeologicTime Scale 2012 Elsevier Boston p 181ndash206

Hadavi F Khosru Tehrani Kh Senemari S 2007 Bio -stratigraphy of Calcareous Nannofossils of Gurpi Forma-tion in North Gachsaran Journal of Earth Science 16 14ndash23

Hadavi F Rasa Ezadi M M 2008 Nannostratigraphy ofGurpi Formation in Dare-Shahr section (SW Ilam) Jour-nal of Applied Geology 4 299ndash308

Hampton M J Bailey H W Gallagher L T MortimoreR N Wood C J 2007 The biostratigraphy of SeafordHead Sussex southern England an international refer-ence section for the basal boundaries for the Santonianand Campanian Stages in chalk facies Cretaceous Re-search 28 46ndash60

Hemmati Nasab M 2008 Microbiostratigraphy and Se-quence Stratigraphy of the Gurpi Formation in Kaaver

Section South of Kabir-kuh Master thesis Faculty ofscience Tehran University 177 pp

Hemmati-Nasab M Ghasemi-Nejad E Darvishzad B2008 Paleobathymetry of the Gurpi Formation based on benthic and planktonic foraminifera in SouthwesternIran Journal of Sciences Islamic Republic of Iran 34157ndash173

Hosseini B 2006 Lithostratigraphy and nannostratigraphyof Gurpi Formation in Mongasht anticline section andKamestan anticline section (Izeh area) Master thesisFaculty of earth science Shahid beheshti University195 pp

James G A Wynd J G 1965 Stratigraphic Nomenclatureof Iranian Oil Consortium Agreement Area AAPG Bul-letin 49 2182ndash2245

Jenkyns H C Gale A S Corfield R M 1994 Carbon-and oxygen-isotope stratigraphy of the English Chalk andItalian Scaglia and its paleoclimatic significance Geo-logical Magazine 131 1ndash34

Jarvis I Mabrouk A Moody R T J de Cabrera S 2002Late Cretaceous (Campanian) carbon isotope events sea-level change and correlation of the Tethyan and BorealRealms Palaeogeography Palaeoclimatolology Palaeo -ecology 188 215ndash248

Jarvis I Gale A S Jenkyns H C Pearce M A 2006Secular variation in Late Cretaceous carbon isotopes anew δ13C reference curve for the CenomanianndashCampan-ian (996ndash706 Ma) Geological Magazine 143 561ndash608

Kennedy W J 1984 Ammonite faunas and the lsquostandardzonesrsquo of the Cenomanian to Maastrictian Stages in theirtype areas with some proposals for the definition of thestage boundaries by ammonites Bulletin of the Geologi-cal Society of Denmark 33(1ndash2) 147ndash162

Lamolda M A Paul C R C 2007 Carbon and Oxygenstable isotopes across the ConiacianSantonian boundaryat Olazagutia northern Spain Cretaceous Research 2837ndash45

Lamolda M A Hancock J M et al 1996 The SantonianStage and substages In Rawson P F et al (Eds) Pro-ceedings ldquoSecond International Symposium on Creta-ceous Stage Boundariesrdquo Brussels September 1995Bulletin de lrsquoInstitut Royal des Sciences Naturelles deBelgique Sciences de la Terre 66 (Supplement) 95ndash102

Martini E 1971 Standard Tertiary and Quaternary cal-careous nannoplankton zonation In Farinacci A (Ed)Proceedings of the II Planktonic Conference Roma1970 Edizioni Tecnoscienza Roma p 739ndash785

Melinte M C Lamolda M A 2007 Calcareous nanno-fossil biostratigraphy of the ConiacianSantonian bound-ary interval in Romania and comparison with other Euro-pean regions Cretaceous Research 28 119ndash127

Melinte-Dobrinescu M C Bojar A-V 2010 Late Creta-ceous carbon- and oxygen isotope stratigraphy nanno-fossil events and paleoclimate fluctuations in the Hategarea (SW Romania) Palaeogeography Palaeoclimatol-ogy Palaeoecology 293 295ndash305

Mitchell S F Ball J D Crowley S F Marshall J DPaul C R C Veltkamp C J Samir A 1997 Isotope


data from Cretaceous chalks and foraminifera Environ-mental or diagenetic signals Geology 25 691ndash694

Molnar M 2006 Tertiary Development of the ZagrosMountains Geol 418 ndash Earth History 21 pp httpwwwuwecedujolhmStudent_ResearchMolnarreportszagrospdf

Montgomery P Hailwood E A Gale A S Burnett J A1998 The magnetostratigraphy of Coniacian-Late Cam-panian chalk sequences in southern England Earth andPlanetary Science Letters 156 209ndash224

Moradi M 2010 Biostratigraphy and paleoecology ofGurpi Formation in Farhad Abad section in the west ofDarreh-shahr Master thesis Faculty of science TehranUniversity 130 pp

Mortimore R N Wood C J Gallois R W 2001 BritishUpper Cretaceous Stratigraphy In Geological Conserva-tion Review Series No 23 Joint Nature ConservationCommittee Peterborough 558 pp

Motiei H (Ed) 1994 Geology of Iran Stratigraphy of Zagros Geological Survey of Iran 536 pp

Nabavi M H (Ed) 1976 An introduction to the geology ofIran Geological Survey of Iran (In Farsi) 110 pp

Nabavi F 2008 Nannostratigraphy of Gurpi Formation inKharameh area (Shiraz) and Burkh mountain (southernLar) Master thesis Faculty of earth science Shahid be-heshti University 165 pp

Ogg J G Hinnov L A Huang C 2012 Chapter 27 ndashCretaceous In Gradstein F et al (Eds) The GeologicTime Scale 2012 Elsevier Boston p 793ndash853

Paul C R C Lamolda M A 2009 Testing the precisionof bioevents Geological Magazine 146(5) 625ndash637

Perch-Nielsen K (1979) Calcareous nannofossils from theCretaceous between the North Sea and the Mediterra -nean IUGS Series A v 6 223ndash272

Perch-Nielsen K 1985 Mesozoic Calcareous Nannofos-sils In Bolli H M Saunders J B Perch-Nielsen K(Eds) Plankton Stratigraphy Cambridge Earth SciencesSeries Cambridge University Press p 329ndash426

Pettijohn F J Potter P E Siever R (Eds) 1975 Sedi-mentary Rocks Harper and Row New-York 628 pp

Rabani R Ghasemi-Nejad A Amini A 2009 Palinostra -tigraphy and sequence stratigraphy of Gurpi Formation invalley Shahr section southeastern of Ilam Iranian Journalof Geology 10 3ndash13

Raffi I 1999 Precision and accuracy of nannofossil bio -stratigraphic correlation Philosophical Transactions ofthe Royal Society of London A 357 1975ndash1993

Roth P H 1978 Cretaceous nannoplankton biostratigra-phy and oceanography of the northwestern AtlanticOcean In Benson W E Sheridan R E et al (Eds) Ini-tial Reports of the Deep Sea Drilling Project 44 731ndash759

Schoumlnfeld J Schulz M-G Arthur M A Burnett JGale A S Hambach U Hansen H J Kennedy W JRasmussen K L Thirlwall M F Wray D S 1996New results on biostratigraphy paleomagnetism geo-chemistry and correlation from the standard section forthe Upper Cretaceous white chalk of northern Germany

(Laumlgerdorf-Kronsmoor-Hemmoor) Mitteilungen des Geologisch-Palaumlontologischen Institutes der UniversitaumltHamburg 77 545ndash575

Schulz M-G Ernst G Ernst H Schmid F 1984 Co-niacian to Maastrichtian stage boundaries in the standardsection for the Upper Cretaceous white chalk of NW Ger-many (Laumlgerdorf-Kronsmoor-Henmoor) Definitions andproposals Bulletin of the Geological Society of Denmark33(1ndash2) 203ndash215

Sepehr M Cosgrove J W 2005 Role of the KazerunFault Zone in the formation and deformation of the Za-gros Fold-Thrust Belt Iran Tectonics 24 doi1010292004TC001725

Shamrock J L Watkins D K 2009 Evolution of the Cretaceous calcareous nannofossil genus Eiffellithus andits biostratigraphic significance Cretaceous Research 301083ndash1102

Sina M A Aghanabati A Kani A L Bahadori A R2010 Biostratigraphy study of Gurpi Formation inPoldokhtar section (Kuh-Soltan anticline) based on cal-careous nannofossils Journal of Earth Science 79 183ndash188

Sissingh W 1977 Biostratigraphy of Cretaceous calcare-ous nannoplankton Geologie Mijnbouw 56 37ndash65

Sprovieri M Sabatino N Pelosi N Batenburg S JCoccioni R Iavarone M Mazzola S 2013 Late Cre-taceous orbitally-paced carbon isotope stratigraphy fromthe Bottaccione Gorge (Italy) Palaeogeography Palaeo-climatology Palaeoecology 379ndash380 81ndash94

Stocklin J Setudehnia A 1970 Stratigraphic Lexicon ofIran Geological Survey of Iran Tehran 18 409

Stoll H M Schrag D P 2000 High-resolution stable iso-tope records from the Upper Cretaceous rocks of Italy andSpain Glacial episodes in a greenhouse planet Geolog-ical Society of America Bulletin 112 308ndash319

Setudehnia A 1972 Stratigraphic Lexicon of Iran UnionInternationale des Sciences Geologiques 315 pp

Takin M 1972 Iranian geology and continental drift in theMiddle East Nature 235 147ndash150

Talbot C J Alavi M 1996 The past of a future syntaxisacross the Zagros in Salt Tectonics Geol Soc SpecPubl 100 89ndash110

Thibault N Gardin S 2007 The late Maastrichtian nanno-fossil record of climate change in the South Atlantic DSDPHole 525A Marine Micropaleontology 65 163ndash184

Thibault N Gardin S 2010 The calcareous nannofossilresponse to the end-Cretaceous warm event in the Tropi-cal Pacific Palaeogeography Palaeoclimatology Palaeo -ecology 291 239ndash252

Thibault N Harlou R Schovsbo N Schioslashler P Mino-letti F Galbrun B Lauridsen B W Sheldon E Stem-merik L Surlyk F 2012a Upper CampanianndashMaas-trichtian nannofossil biostratigraphy and high-resolutioncarbon-isotope stratigraphy of the Danish Basin Towardsa standard δ13C curve for the Boreal Realm CretaceousResearch 33 72ndash90

Thibault N Husson D Harlou R Gardin S GalbrunB Huret E Minoletti F 2012b Astronomical calibra-


tion of upper CampanianndashMaastrichtian carbon isotopeevents and calcareous plankton biostratigraphy in the In-dian Ocean (ODP Hole 762C) Implication for the age ofthe CampanianndashMaastrichtian boundary Palaeogeogra-phy Palaeoclimatology Palaeoecology 337ndash338 52ndash71

Voigt S Friedrich O Norris R D Schoumlnfeld J 2010CampanianndashMaastrichtian carbon isotope stratigraphyshelf-ocean correlation between the European shelf seaand the tropical Pacific Ocean Newsletters on Stratigra-phy 44 57ndash72

Voigt S Gale A S Jung C Jenkyns H C 2012 Glob-al correlation of Upper CampanianndashMaastrichtian suc-cessions using carbon-isotope stratigraphy development

of a new Maastrichtian timescale Newsletters on Strati -graphy 45 25ndash53

Wendler I 2013 A critical evaluation of carbon isotopestratigraphy and biostratigraphic implications for LateCretaceous global correlation Earth-Science Reviews126 116ndash146

Wynd J G 1965 Biofacies of the Iranian Oil ConsortiumAgreement area Iranian Oil Operating Companies Geo-logical and Exploration Division Report 1082 89 pp

Manuscript received December 19 2013 rev version ac-cepted April 15 2014


Samples Height δ13C δ18O CaCO3

(m) permil permil Bernard (PDB) (PDB) method

[]

MB_Pa2 25790 ndash133 ndash353 646MB_Pa1 25691 ndash128 ndash378 768MB_G133 25539 ndash054 ndash422 737MB_G132 25497 ndash050 ndash422 80MB_G131 25290 ndash032 ndash489 645MB_G130 25081 ndash021 ndash452 566MB_G129 24897 ndash040 ndash451 688MB_G128 24730 ndash006 ndash497 606MB_G127 24427 ndash021 ndash473 657MB_G126 24279 ndash112 ndash463 843MB_G125 24070 ndash159 ndash412 826MB_G124 23844 ndash158 ndash421 86MB_G123 23643 ndash161 ndash433 846MB_G122 23400 ndash141 ndash452 794MB_G121 23106 ndash158 ndash433 82MB_G120 22870 ndash151 ndash438 857MB_G119 22575 ndash165 ndash445 671MB_G118 22360 ndash151 ndash464 788MB_G117 22218 ndash163 ndash441 857MB_G116 21980 ndash172 ndash430 894MB_G115 21748 ndash164 ndash436 914MB_G114 21468 ndash153 ndash426 894MB_G113 21215 ndash155 ndash440 891MB_G112 21030 ndash155 ndash397 828MB_G111 20840 ndash138 ndash453 874MB_G110 20661 ndash118 ndash438 868MB_G109 20410 ndash139 ndash394 968MB_G108 20275 ndash119 ndash434 946



[]

MB_G107 20030 142 ndash423 908MB_G106 19762 128 ndash400 828MB_G105 19514 139 ndash412 808MB_G104 19203 135 ndash448 851MB_G103 18890 136 ndash437 783MB_G102 18620 123 ndash439 928MB_G101 18336 131 ndash410 691MB_G100 18109 129 ndash420 897MB_G099 17840 128 ndash442 868MB_G098 17646 148 ndash453 897MB_G097 17375 166 ndash444 897MB_G096 17087 131 ndash447 743MB_G095 16890 160 ndash448 794MB_G094 16699 179 ndash436 791MB_G093 16514 193 ndash424 774MB_G092 16390 182 ndash414 811MB_G091 16193 175 ndash414 80MB_G090 15992 160 ndash422 846MB_G089 15740 165 ndash449 851MB_G088 15561 161 ndash460 883MB_G087 15351 137 ndash414 938MB_G086 15112 168 ndash442 771MB_G085 14930 174 ndash429 814MB_G084 14744 145 ndash454 846MB_G083 14524 150 ndash448 777MB_G082 14314 170 ndash450 843MB_G081 14063 156 ndash441 828MB_G080 13842 161 ndash480 874

Appendix 1 CaCO3 content Bulk carbon and oxygen stable isotopes at Shahneshin section



[]

MB_G079 13613 149 ndash481 76MB_G078 13520 178 ndash447 837MB_G077 13341 169 ndash473 746MB_G076 13138 182 ndash405 828MB_G075 12945 162 ndash444 877MB_G074 12829 172 ndash467 768MB_G073 12644 166 ndash455 897MB_G072 12513 171 ndash472 82MB_G071 12294 177 ndash467 694MB_G070 12028 164 ndash500 854MB_G069 11857 174 ndash501 786MB_G068 11630 167 ndash505 954MB_G067 11397 169 ndash493 826MB_G066 11167 194 ndash497 828MB_G065 10897 180 ndash498 843MB_G064 10688 177 ndash503 908MB_G063 10531 166 ndash490 874MB_G062 10322 168 ndash478 886MB_G061 10080 177 ndash478 754MB_G060 9877 160 ndash487 803MB_G059 9468 157 ndash497 811MB_G058 9461 178 ndash507 794MB_G057 9263 189 ndash445 82MB_G056 9088 177 ndash477 717MB_G055 8883 152 ndash493 68MB_G054 8690 149 ndash503 711MB_G053 8479 156 ndash492 788MB_G052 8233 146 ndash493 771MB_G051 8099 167 ndash506 697MB_G050 7912 149 ndash476 78MB_G049 7743 149 ndash507 766MB_G048 7590 166 ndash521 771MB_G047 7414 137 ndash482 794MB_G046 7180 146 ndash412 708MB_G045 6976 149 ndash493 694MB_G044 6778 111 ndash495 771MB_G043 6580 116 ndash449 788MB_G042 6350 163 ndash500 786MB_G041 6110 163 ndash493 76MB_G040 5977 147 ndash468 76



[]

MB_G039 5860 148 ndash511 777MB_G038 5744 145 ndash495 728MB_G037 5500 146 ndash504 817MB_G036 5272 135 ndash544 823MB_G035 5015 135 ndash492 763MB_G034 4800 145 ndash501 726MB_G033 4492 129 ndash484 728MB_G032 4308 132 ndash483 763MB_G031 4158 120 ndash452 791MB_G030 3890 127 ndash494 648MB_G029 3738 104 ndash518 823MB_G028 3450 151 ndash489 771MB_G027 3346 126 ndash486 848MB_G026 3190 105 ndash465 748MB_G025 2976 112 ndash519 70MB_G024 2770 139 ndash499 803MB_G023 2517 133 ndash505 826MB_G022 2438 155 ndash480 868MB_G021 2241 147 ndash494 831MB_G020 2079 162 ndash491 748MB_G019 1903 170 ndash559 791MB_G018 1720 145 ndash470 906MB_G017 1573 140 ndash488 954MB_G016 1460 103 ndash488 905MB_G015 1274 105 ndash498 863MB_G014 1154 104 ndash518 871MB_G013 951 124 ndash538 723MB_G012 815 131 ndash506 786MB_G011 680 117 ndash521 868MB_G010 584 133 ndash497 797MB_G009 470 149 ndash488 657MB_G008 367 146 ndash514 76MB_G007 290 136 ndash506 751MB_G006 207 147 ndash499 748MB_G005 156 147 ndash515 794MB_G004 086 141 ndash514 906MB_G003 058 147 ndash494 817MB_G002 030 147 ndash491 934MB_G001 000 144 ndash498 837


Appendix 1 Continued

1 Introduction

The Cretaceous of Iran is characterised by a large di-versity of rocks and facies (Nabavi 1976) There are 27 different formations in the Mesozoic of the Zagrosarea 17 of those belong to the Cretaceous (Motiei1994) Sediments from the Cretaceous are well ex-posed in the Zagros basin southwest of Iran with anoverall good continuity and high sedimentation ratesFor a variety of reasons such as oil and gas reservoirsin Mesozoic and Cenozoic deposits numerous studieshave been focused on the formation of the basin (Mol-nar 2006 Talbot and Alavi 1996 Sepehr and Cosgrove2005) The Gurpi Formation which spans the LateCretaceous (SantonianndashMaastrichtian) to Paleocenein the west and southwestern part of the Zagros basinpredominantly consists of shales and marls (Stocklinand Setudehnia 1970) The Gurpi Formation is highlyfossiliferous and for this reason has been extensivelystudied for different biostratigraphical aspects Nu-

merous studies in the Zagros folded zone reveal sig-nificant lateral changes in the thickness age and litho-logical composition of the Gurpi Formation (Ghasemi-Nejad 2006 Hosseini 2006 Nabavi 2008 Asleshirin2011) The present study focuses on the Shahneshinsection of the Gurpi Formation in the west of the Za-gros Basin (Fig 1) The aim of the study is to establisha solid stratigraphic framework of the Shahneshin sec-tion based on calcareous nannofossils and bulk carbonstable isotopes and to provide correlations to other areas and oceanic basins spanning the same interval(Fig 2) The Late Cretaceous of this area remains apoorly known part of the Tethyan Realm and can im-prove the knowledge on calcareous nannofossil andstable isotope stratigraphy for the considered time in-terval which is mostly well-documented from Euro-pean and North American sections (Jenkyns et al1994 Jarvis et al 2002 2006 Sprovieri et al 2013Thibault et al 2012a Voigt et al 2010 2012) Strati-graphic correlations to other reference sections for this


Fig 1 Location and geological map of the studied area After the Geological map of Kazerun at 1100000









3 Methods





32 Stable isotopes





4 Results

































5 Discussion













Fig

6

Cor

rela

tion

of th

e C

onia

cian

to e

arly

Cam

pani

an δ

13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

of th

e E

nglis

h ch

alk

(1)

A p

ossi

ble

re-

vise

d in

terp

reta

tion

of t

he m

agne

tost

ratig

raph

y of

Mon

tgom

ery

et a

l (1

998)

is

prop

osed

her

e fo

r th

e E

nglis

h ch

alk

base

d on

the

cor

rela

tion

of t

he S

CB

E t

o th

e G

ubbi

ore

cord


Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns































6 Conclusions













References























































































[]




[]





[]




[]












3 Methods





32 Stable isotopes





4 Results

































5 Discussion













Fig

6

Cor

rela

tion

of th

e C

onia

cian

to e

arly

Cam

pani

an δ

13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

of th

e E

nglis

h ch

alk

(1)

A p

ossi

ble

re-

vise

d in

terp

reta

tion

of t

he m

agne

tost

ratig

raph

y of

Mon

tgom

ery

et a

l (1

998)

is

prop

osed

her

e fo

r th

e E

nglis

h ch

alk

base

d on

the

cor

rela

tion

of t

he S

CB

E t

o th

e G

ubbi

ore

cord


Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns































6 Conclusions













References























































































[]




[]





[]




[]




32 Stable isotopes





4 Results

































5 Discussion













Fig

6

Cor

rela

tion

of th

e C

onia

cian

to e

arly

Cam

pani

an δ

13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

of th

e E

nglis

h ch

alk

(1)

A p

ossi

ble

re-

vise

d in

terp

reta

tion

of t

he m

agne

tost

ratig

raph

y of

Mon

tgom

ery

et a

l (1

998)

is

prop

osed

her

e fo

r th

e E

nglis

h ch

alk

base

d on

the

cor

rela

tion

of t

he S

CB

E t

o th

e G

ubbi

ore

cord


Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns































6 Conclusions













References























































































[]




[]





[]




[]




























5 Discussion













Fig

6

Cor

rela

tion

of th

e C

onia

cian

to e

arly

Cam

pani

an δ

13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

of th

e E

nglis

h ch

alk

(1)

A p

ossi

ble

re-

vise

d in

terp

reta

tion

of t

he m

agne

tost

ratig

raph

y of

Mon

tgom

ery

et a

l (1

998)

is

prop

osed

her

e fo

r th

e E

nglis

h ch

alk

base

d on

the

cor

rela

tion

of t

he S

CB

E t

o th

e G

ubbi

ore

cord


Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns































6 Conclusions













References























































































[]




[]





[]




[]












Fig

6

Cor

rela

tion

of th

e C

onia

cian

to e

arly

Cam

pani

an δ

13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

of th

e E

nglis

h ch

alk

(1)

A p

ossi

ble

re-

vise

d in

terp

reta

tion

of t

he m

agne

tost

ratig

raph

y of

Mon

tgom

ery

et a

l (1

998)

is

prop

osed

her

e fo

r th

e E

nglis

h ch

alk

base

d on

the

cor

rela

tion

of t

he S

CB

E t

o th

e G

ubbi

ore

cord


Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns































6 Conclusions













References























































































[]




[]





[]




[]





Fig

7

Cor

rela

tion

of th

e C

onia

cian

ndashM

aast

rich

tian

δ13C

cur

ve a

t Sha

hnes

hin

with

ref

eren

ce r

ecor

ds f

or th

e L

ate

Cre

tace

ous

at G

ubbi

o (I

taly

) an

d in

the

Ger

man

cha

lk

and

with

the

rece

nt c

ompi

led

stac

k of

Wen

dler

(20

13)

(1)

The

Cre

tace

ous

CC

bio

zona

tion

is th

at o

f Si

ssin

gh (

1977

) m

odif

ied

by P

erch

-Nie

lsen

(19

85)

The

UC

bio

zona

-tio

n is

fro

m B

urne

tt (1

998)

and

the

sub

zona

tion

corr

espo

nds

to t

he s

chem

e fo

r th

e Te

thya

n re

alm

(T

P) (

2) I

n th

e G

erm

an c

halk

the

cal

care

ous

nann

ofos

sil

bioz

onat

ion

used

is th

e U

C s

chem

e fo

r th

e B

orea

l rea

lm (

BP)

fro

m B

urne

tt (1

998)

(3)

Det

aile

d B

orea

l mac

rofo

ssil

zone

s ca

n be

fou

nd in

Sch

ulz

et a

l (1

984)

(4)

The

LO

of

Ee

xim

-iu

sat

Gub

bio

corr

espo

nds

here

to th

e le

vel i

dent

ifie

d in

the

Bot

tacc

ione

sec

tion

by G

ardi

n et

al

(201

2) s

ituat

ed ~

11m

bel

ow th

e L

O o

f pl

ankt

ic f

oram

inif

er R

cal

cara

-ta

and

proj

ecte

d at

a s

imila

r he

ight

on

the

Con

tess

a re

cord

ass

umin

g si

mila

r se

dim

enta

tion

rate

s be

twee

n th

e tw

o se

ctio

ns































6 Conclusions













References























































































[]




[]





[]




[]


































6 Conclusions













References























































































[]




[]





[]




[]












References























































































[]




[]





[]




[]













































































[]




[]





[]




[]






[]




[]




Coniacian-Maastrichtian calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy in...

Documents

Transcript of Coniacian-Maastrichtian calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy in...