Cretaceous Research 91 (2018) 312e340

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Integrated bio- and carbon-isotope stratigraphy of the Upper Cretaceous Gurpi Formation (Iran): A new reference for the eastern Tethys and its implications for large-scale correlation of stage boundaries Mohammad J. Razmjooei a, b, *, Nicolas Thibault b, Anoshiravan Kani a, at d, Samira Shahriari a, Wiesława Radmacher e,
s-Turell c, Emmanuelle Puce Jaume Dinare f ophile Cocquerez d Amir Mohammad Jamali , Clemens V. Ullmann g, Silke Voigt h, The a

Department of Geology, Faculty of Earth Science, Shahid Beheshti University, Tehran, Iran Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark c Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, I-00143 Rome, Italy d Biog eosciences, UMR 6282, CNRS, University of Burgundy Franche-Comt e, 6 boulevard Gabriel, Dijon F-21000, France e Institute of Geological Sciences, Polish Academy of Sciences, Research Centre in Cracow, St. Senacka No. 1, PL-31002, Poland f National Iranian Oil Company, Exploration Directorate, Tehran, Iran g Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Penryn, TR10 9FE, UK h €ferallee 1, 60438 Frankfurt, Germany Institute of Geosciences, Goethe University Frankfurt, Altenho b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 17 November 2017 Received in revised form 6 April 2018 Accepted in revised form 4 July 2018 Available online 7 July 2018

A high-resolution stratigraphic analysis of the Upper Cretaceous Gurpi Formation has been undertaken in the Shahneshin section (Zagros Basin, Iran). New results on calcareous nannofossils, planktic foraminifers, dinoflagellate cysts and high-resolution carbon and oxygen stable isotopes form the basis of a reference section for the eastern Tethys that spans the upper Coniacian to the late Danian. Carbonisotope correlation to Gubbio, Italy and the NW German chalk allows for the identification of many isotopic events as well as for the definition of new events in the Campanian and Maastrichtian. Our results allow for a review of the accurate position of the Coniacian/Santonian, Santonian/Campanian, and Campanian/Maastrichtian stage boundaries relative to carbon isotopes and plankton bioevents. The reliability of Coniacian to Maastrichtian planktic foraminifer, dinoflagellate cysts and calcareous nannofossil biohorizons is assessed. © 2018 Elsevier Ltd. All rights reserved.

Keywords: ConiacianeMaastrichtian Calcareous nannofossils Planktic foraminifera Dinoflagellate cysts Carbon isotopes Tethyan realm Zagros

1. Introduction Numerous studies have been performed that integrate the biostratigraphy, magnetostratigraphy, and carbon-isotope stratigraphy of various Upper Cretaceous deep-sea sites, as well as shallower European and American sections. These studies have considerably improved local stratigraphy as well as provided reliable data and ages for the Geologic Time Scale (Li and Keller, 1998a; Jarvis et al., 2002, 2006; Lamolda et al., 2007; Friedrich et al., 2009,

* Corresponding author. E-mail addresses: [email protected], [email protected] (M.J. Razmjooei). https://doi.org/10.1016/j.cretres.2018.07.002 0195-6671/© 2018 Elsevier Ltd. All rights reserved.

2012; Voigt et al., 2010, 2012; Husson et al., 2011, 2012, 2014; Batenburg et al., 2012, 2014; Gardin et al., 2012; Thibault et al., 2012a, 2012b, 2015, 2016a, 2016b, 2016c; Sprovieri et al., 2013;
s-Turell et al., 2013; Joo Surlyk et al., 2013; Wendler, 2013; Dinare and Sageman, 2014; Lamolda et al., 2014; Coccioni and PremoliSilva, 2015; Boussaha et al., 2016; Chenot et al., 2016, 2018; Larina et al., 2016; Perdiou et al., 2015; Dubicka et al., 2017). However, the Late Cretaceous of the eastern Tethyan realm is still poorly documented as compared to its western counterparts. In western to southwestern Iran, the sediments of the Zagros Basin outcrop extensively. Despite numerous biostratigraphic studies performed in this area by oil companies as well as by various research institutes and investigators on different fossil groups (e.g.,

M.J. Razmjooei et al. / Cretaceous Research 91 (2018) 312e340

foraminifers: Etemad et al., 2008 and Hemmati-Nasab et al., 2008; calcareous nannofossils: Hadavi and Rasa Ezadi, 2008; and Sina et al., 2010; palynomorphs: Ghasemi-Nejad et al., 2006; Abrari et al., 2011 and Beiranvand et al., 2013), few published studies have calibrated the biostratigraphy of different fossil groups on the same sections (Ghasemi-Nejad et al., 2006; Senemari et al., 2010) or integrated the biostratigraphy with carbon-isotope stratigraphy (Razmjooei et al., 2014). Such studies are, however, necessary as a number of calcareous nannofossil and planktic foraminifer biohorizons have been demonstrated to be time-transgressive across different latitudes and oceanic basins, particularly during the CampanianeMaastrichtian (Nelson et al., 1991; Huber and Watkins, 1992; Barrera, 1994; Chauris et al., 1998; Thibault and Gardin, 2010; Thibault et al., 2010, 2012a, 2012b, 2015; Gardin et al., 2012; Farouk, 2014; Guerra et al., 2016; Farouk et al., 2018; Sabatino et al., 2018). The standard Late Cretaceous scheme has been largely developed on the basis of central Tethyan deposits in Italy (Coccioni and Premoli-Silva, 2015, and references therein). To test the applicability of that scheme to deposits of the eastern Tethys, it is necessary to conduct integrated stratigraphic studies in the eastern parts of the region as well. The Gurpi Formation constitutes a good candidate for such studies, as it is very well exposed, expanded and chronostratigraphically covers the upper Coniacian to Maastrichtian stages with substantial continuity, although macroinvertebrate fossils are only recorded in limited areas and stratigraphic intervals (Senemari and Azizi, 2012; Razmjooei et al., 2014). A previous attempt to calibrate calcareous nannofossil biostratigraphy with carbon-isotope stratigraphy of the Gurpi Formation was undertaken by Razmjooei et al. (2014) using the Shahneshin Section. Additionally, large-scale correlations between Zagros and other reference sections in Europe were proposed. However, this preliminary study lacked a detailed lithological description of the studied section, the biostratigraphy was limited solely to calcareous nannofossils and the resolution of the carbon isotope curve was not as high as the resolution of the reference sections in NW Europe.

313

In this study, we present a new detailed lithological description of the Shahneshin Section, along with a higher resolution carbon stable isotope profile and new biostratigraphic data on calcareous nannofossils, dinoflagellate cysts and planktic foraminifera to establish a solid stratigraphic framework of the Gurpi Formation that allows large-scale correlations.

2. Geological setting The Shahneshin Section is situated on the southern flank of the Shahneshin Anticline north to northwest of Abul Hayat Gorge (western Fars Province, located northeast of Kazerun). A new section logging and sampling campaign was conducted in 2016 and our first and last samples were collected at the following coordinates: N29
440 4700 ; E51
460 3100 and N29
440 40.6900 ; E51
460 26.8700, respectively (Fig. 1). The Shahneshin section was selected for study as a potential reference for the Gurpi Formation for the following reasons: 1. The section presents a continuous exposure from the upper Coniacian to the end of the Maastrichtian with spectacular carbonate cycles (Fig. 2). 2. Outcrop conditions are excellent with no parts of the section covered and no evidence of major faulting. 3. The section consists of fossiliferous marls and marly limestones containing various microfossils, such as nannofossils, benthic and planktic foraminifera as well as dinoflagellate cysts (Fig. 3). 4. The lower and the upper boundaries of the Gurpi Formation are readily identified by clear lithostratigraphic markers and are not covered. 5. The section is easily accessible as it is close to an inhabited area and an asphalt road passes through the base of the section. The overlying Paleogene Pabdeh and Oligocene-Miocene Asmari formations are also suitable outcrops of the Cenozoic strata in this

Fig. 1. The Campanian paleogeography of the Middle East (on the left, after Barrier et al., 2008) and the location and modern geological map of the studied area (on the right).

314

Ridge L

SE

Ridge O

O

338

75

75

N 321 o

/

SW

39

Ri

Ridge H

ge CSW

SE

ge B

Rid

Rid

SW

NW

dg

M 291

eK

Shahneshin section

L

271

Gurpi Formation

K

Gurpi F. Ilam F.

J

259

238 o

I 221

30 W/

H

G

201

186

5S

F

E

171

154

o

7

75

/ SW

30

o

70

S

2 W/

9

D 133

C 108 o

B

91

/ 27

SW

7

Maastrichtian

/ 25 o

75 S

Campanian

A

o

W 5S

Santonian

36

9 W/ 1

Road

75

11

Coniacian

Fig. 2. The outcrop at Shahneshin with main ridges (A to O). Numbers correspond to meters in section. The strike and dip are indicated for various bed ridges.

o

80 SW

/15

Ilam tion a Form

M.J. Razmjooei et al. / Cretaceous Research 91 (2018) 312e340

349

e h on o b d ati 1 a /4 P orm W S F

SW

SW

UC 19 U C20

b

C33N

Gurpi

G. ventricosa

T. variecalamum

bloom of bentic foraminifera such as Gavelinella spp., Lenticulina spp., Marssonella spp. and Gyroidinoides spp.

X. ceratioides P. australinum + C. diebelii

244 m bloom of bentic foraminifera 232 m such as Gavelinella spp. and Neoflabelina spp.

G

180

Purple shale

C. verbeekii R. anthophorus U. gothicus B.hayi C. aculeus

Dark gray marl with intercalation of dark gray argillaceous limestone Pale gray marl with intercalation of light yellow argillaceous limestone Dark gray argillaceous limestone with intercalation of dark gray marl

G. ventricosa

C. verbeekii

limestone

D 120

C 100

H. hexalithus M. furcatus B. parca constricta B. hayi M. coronata B. parca parca D. asymetrica R. levis Globotruncana spp. G. elevata

60

Fe

Fe

Dark gray marl with greenish background Iron oxide nodules

Fe

O. operculata

54 m 50 m

A

40

LEGEND

Light yellow argillaceous limestone with intercalation of pale gray marl

C. plummerae

A.cymbiformis

140

D. asymetrica

CC 20

H

200

80

UC 11c - UC 13

bloom of Marssonella spp. and Nodosarella spp. bentic foraminifera

C. obscurus L. cayeuxi

20

D. asymetrica

a-b

UC 11

CC 15

287 m

U. sissinghii

B

c

C. reticulata

B. parca parca

I

220

E

G. elevata

UC 14

b-c

CC 17

CC 18

J

160

UC 14d UC 15a

CC 19

lower

Santonian

a

C. contusa R. fructicosa

P. palpebra M B. parca constricta G. gansseri + G. aegyptica U. trifidus G. havanensis L Curved spine G. falsostuari K E. eximius U. trifidus R. cf. R. L. grillii calcarata Curved spine

F

CC 16

Coniac.

260

c

c

a

280

240

b

M. praemurus T. orionatus

d-e

a

A. mayaroensis

L. quadratus + M. murus Z. bicrescenticus R. levis

300

?R. calcarata G. gansseri integrated zone

UC17

C. kamptneri

N

-

UC 15

CC 21

CC22

Lithology

Samples

A. m oe ay ns ar is -

CC 25a CC26a

b

a

O

320

n co C. sa u t CC 24 UC18

CC 23 upper

b

P. cf. P. hantkerinoides P. hariaensis

340

aensis

Palynomorph Biohorizons

M.J. Razmjooei et al. / Cretaceous Research 91 (2018) 312e340

Campanian

d P. hari-

c

UC 16

Maastrichtian upper lower

CC25c

M. prinsii

Pa

NP 3 CC26b

Thickness (m)

bd

eh

Formation

Foraminifer Zonation

Nannofossil Zonation

Stage

NP 4 Danian

Foraminifer Biohorizons

Nannofossil Biohorizons

360

Ilam

Fe

Fe

Fe

Fig. 3. Log and description of the Shahneshin stratigraphic section. Main biohorizons for Calcareous nannofossils (CN), Planktic foraminifera (PF) and Dinoflagellate cysts (DC) are indicated.

315

D. conca -vata ?

0

316

M.J. Razmjooei et al. / Cretaceous Research 91 (2018) 312e340

Fig. 4. Calcareous nannofossils of the Gurpi Formation in the Shahneshin section. A. Watznaueria barnesae (XPL), sample 10; B. Micula staurophora (XPL), sample 10; C. Cribrosphaerella ehrenbergii (XPL), sample 2498; D. Microrhabdulus undosus (XPL), sample 2498; E. Retecapsa angustiforata (XPL), sample 928; F. Lucianorhabdus cayeuxii (XPL), sample 142; G. Calculites obscurus (XPL), sample 2418; H. Marthasterites furcatus (PPL), sample 10; I. Broinsonia parca parca (XPL), sample 1008; J. Broinsonia parca constricta (XPL), sample 1008; K & L. Ceratolithoides aculeus (K: XPL, L: PPL), sample 2300; M & N. Eiffellithus eximius (XPL, N: rotated), sample 535; O. Uniplanarius trifidus (XPL), sample 2418; P. Tranolithus orionatus (XPL), sample 2418; Q. Reinhardtites levis (XPL), sample 745; R. Zeugrhabdotus bicrescenticus, sample 10; S. Lithraphidites quadratus, sample 3160; T. Micula prinsii, sample 3291.

M.J. Razmjooei et al. / Cretaceous Research 91 (2018) 312e340

area (see, Rahmani et al., 2012; Jafar Nezhad et al., 2015; Taheri et al., 2017).

317

Table 1 Main recorded biohorizons for the ConiacianeMaastrichtian of the Shahneshin section.

3. Methods

Horizons

3.1. Sampling

K-Pg transition 345.7 FO T. operculata (CN) and FO P. cf. 345.25 P. hantkeninoides (PF) FO M. prinsii (CN) 343.95 FO P. hariaensis (PF) 333 FO C. kamptneri (CN) 324 FO L. quadratus (CN) and 320 FO M. murus (CN) FO A. mayaroensis (PF) 317 FO M. praemurus (CN) and 315 M. premolisilvae (CN) LO G. linneiana (PF) 317 FO C. amplector (CN) 311 LO C. reticulata (DC) 310 LO Z. bicrescenticus (CN) 308.5 FO C. contusa (PF) 301 LO R. levis (CN) 303 FO R. fructicosa (PF) 296 LO T. orionatus (CN) 299 FO P. palpebra (CN) 291 LO B. parca constricta (CN) 295 FO T. scotti (PF) 290 FO M. cf. M. swastica (CN) 284.4 FO R. hexacamerata (PF) 284 LO U. sissinghii (CN) and 283 LCO U. trifidus (CN) LO U. gothicus (CN) 283 CampanianeMaastrichtian boundary level FO G. gansseri (PF) and G. aegyptiaca (PF) 274 FO C. indiensis (CN) 276.4 LO T. variecalamum (DC) 275 FO G. havanensis (PF) 262 LO X. ceratioides (DC) 265 LO curved spine (CN) 260.2 LCO E. eximius (CN) 254 FO/LO R. cf. R. calcarata (PF) 245 FO C. diebelii (DC) 245 FO U. trifidus (CN) 246 LO L. grillii (CN) 246 FO curved spine (CN) 243 LO R. anthophorus (CN) 236.2 LO G. elevata (PF) 232 LO B. parca parca (CN) 228 FO U. sissinghii (CN) 206 LO C. verbeekii (CN) 200 FO U. gothicus (CN) 195.7 LCO B. hayi (CN) 174 FO C. plummerae (PF) 160 FO C. aculeus (CN) 162 FO A. cymbiformis (CN) 146 FO G. ventricosa (PF) 130 FO C. verbeekii (CN) 132.9 LO H. hexalithus (CN) 122 LO M. furcatus (CN) 113 FO B. parca constricta (CN) 107 LO C. operculata (DC) 100 FO B. hayi (CN) 98 LO M. coronata (PF) 94 SantonianeCampanian boundary level LO D. asymetrica (PF) 88 FO G. linneiana (PF) 81 FO B. parca parca (CN) 83.7 FO R. levis (CN) 79 LO W. baltica (PF) 76 FO G. elevata (PF) 54 FO C. obscurus (CN) 22 ConiacianeSantonian boundary level FO L. cayeuxii (CN) 18 FO H. hexalithus (CN) 7 FO D. asymetrica (CN) 0.1

The Shahneshin Section was carefully measured and logged using a Jacob's staff. In order to get the least altered material, each sample was taken after digging a few centimeters (up to 15 cm) orthogonally to the strata. A total of 353 samples (1 sample/meter) were selected for analysis of carbon and oxygen isotopes on bulk carbonates, 170 samples were selected for calcareous nannofossil biostratigraphy (with ae2 m resolution), 69 samples were selected for foraminifer biostratigraphy (5e6 m resolution) and 30 samples were selected for dinoflagellate cyst biostratigraphy. The variation in sampling density is a function of the ease and expensive of sample preparation. 3.2. Calcareous nannofossil assemblages For calcareous nannofossil analysis, the samples were prepared by Bown and Young's (1998) smear slide technique at the Nannofossil Laboratory, Faculty of Earth Sciences, Shahid Beheshti University (Tehran, Iran) where slides are deposited and stored, and where they were studied with a binocular microscope (Eclipse E200 pol) at 1000 magnification (Fig. 4). The CC biozonation of Sissingh (1977) modified by Perch-Nielsen (1985) and the UCTP (Tethyan Province) of Burnett (1998) were applied, using the taxonomic concepts of Perch-Nielsen (1985) and Young and Bown (1997). The taxonomic concepts of Shamrock and Watkins (2009) were considered for the genus Eiffellithus. The calcareous nannofossil zonations are based on first (FO) and last occurrences (LO) and in some cases last consistent occurrence (LCO) of significant taxa (Table 1, range chart available in Appendix 1). The concept of LCO applied in this study corresponds to the stratigraphic level above which taxa become inconsistently recorded in overlying samples and with distinctively lower abundances. 3.3. Planktic foraminifer assemblages For foraminifer analysis, 69 washed samples and 5 thin sections with an average sample spacing of ~5 m were studied. The samples were processed at the Sedimentology Laboratory, Faculty of Earth Sciences, Shahid Beheshti University (Tehran, Iran). Approximately 100 g of each sample was put in a metal container and submerged in water with a few drops of acetic acid with 0.5% concentration. The samples were then soaked in water for several days and disintegrated into smaller pieces through the freeze/thaw process. The resulting disaggregated samples were washed through a