Arabian Journal of Geosciences Reconstruction of the Late Cretaceous-Paleocene paleoenvironment (northern Tunisia) from biostratigraphy, geochemistry and clay mineralogy. --Manuscript Draft--
Manuscript Number:
AJGS-D-15-00548R1
Full Title: Article Type:
Original Paper
Corresponding Author:
Moufida BEN M'BAREK JEMAÏ, Assistant Professor Faculty of Sciences of Bizerte Bizerte, TUNISIA
Corresponding Author Secondary Information: Corresponding Author's Institution:
Faculty of Sciences of Bizerte
Corresponding Author's Secondary Institution: First Author:
Moufida BEN M'BAREK JEMAÏ, Assistant Professor
First Author Secondary Information: Order of Authors:
Moufida BEN M'BAREK JEMAÏ, Assistant Professor Narjess Karoui-Yaakoub, Assistant professor Ali Sdiri, Assistant Professor Rim Azouzi, PhD Joelle Duplay, Professor Lassed Ben Aissa, Assistant Professor
Order of Authors Secondary Information: Funding Information: Abstract:
A multidisciplinary approach was adopted for the reconstitution of the depositional environments based on clay minerals distribution, biostratigraphy and geochemical properties of the Late Cretaceous-Paleocene deposits. Evolution of the mineralogical compositions (i.e., clay minerals contents) was ascertained in two main cross sections from the Late Cretaceous and Paleocene belonging to different paleogeographic domains; the Bir M'Cherga (Tunisian Dorsal) and Tajerouine (Northern West of Tunisia) study sites. Chemical analysis of the original clay samples collected in both sites (i.e., Late Cretaceous and Paleocene clays) showed significant amounts of oxides including calcium, silica, alumina and iron. Three distinct mineralogical zones were identified. Clay mineral assemblages of the Late Cretaceous showed the predominance of kaolinite, subordinated by variable proportions of illite and smectite. In contrast, those of Paleocene clearly showed the predominance of smectite to the detriment of kaolinite and illite. The predominance of kaolinite in the Late Cretaceous clay deposits indicated a calm and shallow depositional environment influenced by hot and wet climate, especially in northeastern Tunisia (Bir M'Cherga study site). Kaolinite typically forms under lacustrine environment where appreciable movement of water would be expected, leading to the development of kaolinite. During Paleocene, the smectite enriched mineralogical procession suggested similar climatic conditions with further deepening of the depositional environment in salt lakes. The correlation and regional geodynamic context of the two studied sections showed an important Maastrichtian unconformity with a Paleocene major hiatus extending from the East to the West.
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Paleoenvironmental reconstruction of the Late
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Cretaceous-Paleocene deposition (northern Tunisia)
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based on biostratigraphy, geochemistry and clay
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mineralogy.
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Moufida Ben M’Barek Jemaï (a), Narjess Karoui Yaakoub(a) , Ali Sdiri(b), Rim Azouzi(c), Raja
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Cherni(a), Lassed Ben Aissa (a), Joelle Duplay(d)
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(a) Department of Earth Sciences, University of Sciences of Bizerte, Tunisia Zarzouna 7021.
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(b) Department of Georessources and Environment, National Engineering School, University of Sfax, Sfax 1173-3038, Tunisia.
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(c) Georesources Laboratory, CERTE-University El Manar 43 Address BP-273, Soliman 8023, Tunisia
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(d) EOST, Laboratory of Hydrology and Geochemistry of Strasbourg, 1 St Blessig 67084 Strasbourg cedex, France
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Abstract
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A multidisciplinary approach was adopted for the reconstitution of the depositional
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environments based on clay minerals distribution, biostratigraphy and geochemical properties
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of the Late Cretaceous-Paleocene deposits. Evolution of the mineralogical compositions (i.e.
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clay minerals contents) was ascertained in two main cross sections from the Late Cretaceous
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and Paleocene belonging to different paleogeographic domains; the Bir M’Cherga (Tunisian
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Dorsal) and Tajerouine (Northern West of Tunisia) study sites. Chemical analysis of the
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original clay samples collected in both sites (i.e. Late Cretaceous and Paleocene clays)
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showed significant amounts of oxides including calcium, silica, alumina and iron. Three
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distinct mineralogical zones were identified. Clay mineral assemblages of the Late Cretaceous
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showed the predominance of kaolinite, subordinated by variable proportions of illite and
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smectite. In contrast, those of Paleocene clearly showed the predominance of smectite to the
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detriment of kaolinite and illite.
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The predominance of kaolinite in the Late Cretaceous clay deposits indicated a calm and
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shallow depositional environment influenced by hot and wet climate, especially in
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northeastern Tunisia (Bir M’Cherga study site). Kaolinite typically forms under lacustrine
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environment where appreciable movement of water would be expected, leading to the
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development of kaolinite. During Paleocene, the smectite enriched mineralogical procession
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suggested similar climatic conditions with further deepening of the depositional environment
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in salt lakes. The correlation and regional geodynamic context of the two studied sections
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showed an important Maastrichtian unconformity with a Paleocene major hiatus extending
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from the East to the West.
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Keywords: deposits, mineralogy, clays, geochemistry, biostratigraphy, northern Tunisia.
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1- Introduction
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There are relatively few studies that detail long-term climate and sea-level changes during the
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Late Cretaceous and Paleocene which was generally assumed to have been equally warm.
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Recent studies, however, have revealed that the Maastrichtian global climate was significantly
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cooler than during the earlier Cretaceous (Axelrod 1984; Speijer 1994; Daoudi et al 2002;
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Adatte 1995; Adatte et al 2000; Adatte et al. 2002; Guasti et al. 2005; Cherni 2008; Karoui-
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Yaakoub 2006; Karoui-Yaakoub al. 2011; Srivastava 2013). Strong climate and temperature
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fluctuations mark the Late Campanian and Maastrichtian. The first major global cooling
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occurred between 71 and 73 Ma and decreased intermediate water temperatures by 5-6°C and
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surface temperatures by 4-5°C in middle and high latitudes. Between 68.5 and 70 Ma,
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intermediate waters warmed by 2°C. Global cooling resumed between 68.5 and 65.5 Ma when
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intermediate water temperatures decreased by 3- 4°C and sea surface temperatures decreased
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by 5°C in middle latitudes. About 450-200 ka before the Cretaceous Paleogene (K/Pg)
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boundary rapid global warming increased intermediate and sea surface temperatures by 3-
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4°C, though sea surface temperatures changed little in low latitudes (Li and Keller 1998b).
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Beginning about 200 ka before the end of the Maastrichtian, climate cooled rapidly by 2-3°C
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in both surface and intermediate waters and warmed again during the last 50-100 ka of the
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Maastrichtian (Li and Keller 1998b). In the current study we are interested at the sedimentary
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paleoenvironment study and the global climatic changes in the Late Cretaceous and the
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Paleocene. This study is based on the mineralogical analyses, geochemical of clays, and the
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microfaunal associations. Based on these results we have identified the climatic variations in
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Late Cretaceous and Paleocene in regions of Bir M’Cherga and Tajerouine. At that time a
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change in sea level during on the Late Cretaceous at Paleocene at Tajerouine to the Bir
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M'Cherga is noted.
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In addition, climatic changes inferred from clay mineral contents correlate with sea-level
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changes. Warm or humid climates accompany high sea-levels and cooler or arid climates
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generally accompany low sea-level (Li et al. 2000). The global sea-level fluctuations are
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linked to climatic changes (Li et al. 1999) and inversely correlate with species diversity in
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planktonic foraminifera (e.g. diversity maximum follows maximum cooling at 70.7-70.3 Ma;
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diversity decline follows warming at 65.4-65.2 Ma, Li and Keller 1998a, c).
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Few studies have correlated clay mineral contents to palaenvironmental changes (Adatte et al.
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2002; Chamley 1979; Daoudi et al. 1995; Daoudi and Deconinck 1994; Duffaud 1960).
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Therefore, more detailed information is needed to assess the relationship between the 3
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mineralogical, physicochemical characteristics of clay deposits, and the microfaunal
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associations. In this study, particular attention has been devoted to the assessment of the
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physicochemical characteristics of clays from Late Cretaceous and Paleocene of Bir
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M’Cherga and Tajerouine and their depositional environments. It is to be mentioned that this
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the first study that highlighted the palaeoenvironmental deposition of the Late Cretaceous-
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Paleocene clays of northern Tunisia
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2-Materials and methods
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2-1- Studied material and locations
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More than fifty samples were collected in two reference sections of northern Tunisia (Fig. 1):
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The Bir M’Cherga section located 30km to the south of Tunis and Tajerouine site near the
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Kef town. The Bir M’Cherga section lies between the Oudna archaeological site to the west,
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and the Zaghouan city to the Eastern edge of the Bir M’Cherga (Jauzein 1957 and 1967)
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Coordinates: XA= 363,5; YA= 520,5; XB=364; YB= 522).
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The Tajerouine section, belonging to the Kef district (38km towards Tunisian-Algerian
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borders), is limited by the high reliefs of Thala to the south and those of the Kef to the north
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(Lambert coordinates XA= 382; YA= 383; XB=287; YB= 286, Tajerouine map N°51, 1/50
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000). It consisted of a thick marly series of the Upper Maastrichtian- Paleocene system to the
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south-western flank of Jebel Houdh covered by the Eocene limestone bed (Burollet and
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Sainfeld 1956).
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2-2-Methodology
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To reconstruct the paleoenvironmental deposition of the Late Cretaceous and Paleocene clays,
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we used several techniques:
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Chemical analysis by AAS
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Chemical analysis was carried out by atomic absorption spectroscopy (AAS) using a Perkin-
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Elmer apparatus with peroxide acetylene flame. This analysis allowed the determination of
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the major elements relative percentages (i.e. SiO2, Al2O3, Fe2O3, CaO, K2O, MgO, Na2O, and
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SO4) and loss on ignition.
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Mineralogical analysis by XRD
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Mineralogical analysis of the collected clay samples was determined by X-ray diffraction
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analysis using a Philips PW 1730 diffractometer equipped with Cu-Kα filter. XRD patterns of
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the original clays were obtained for randomly oriented powders (< 40μm sized fraction); those
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of the clay fraction subsamples (< 2μm) were determined on oriented pastes as followings: (1)
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without pretreatment (air dried), (2) saturated with ethylene glycol and (3) heated to 550°C
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for two hours. Percentages of clay species were obtained from the relative height of the 001
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reflection (Ben M’Barek et al. 2002; Baccour et al. 2008; Jeridi et al. 2008) recorded on the
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diffractograms of the oriented pastes (Moore and Reynolds 1989). Recorded on the
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diffractograms of the oriented pastes (Moore and Reynolds 1989).
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Biostratigraphic analysis
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For the biostratigraphic study, collection of foraminifera on 150 and 60µm sieves was
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undertaken using standard washing methods according to Loeblich and Tappan (1988) and
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Toumarkine and Luterbacher (1985).
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3- Geological settings
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The study sections belong to two different paleogeographic and structural domains. The Bir
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M’Cherga area belongs to the Tunisian Trough characterized by NE-SW to N-S anticline
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ranges (Jauzein 1967; Zargouni 1975 and Marzougui et al. 2014). Those features are affected
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by E-W treading major faults (Burolet 1956; Ben Ayed 1993 and Boukadi 1994) associated to
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orthogonal subsiding basins. The structural pattern includes main linear axis parallel to the
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major fault of Tunisian Trough and orthogonal to the NE-SW folding system of the Atlasic
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tectonic phase (Aridhi et al. 2014). On the other hand, the Tajerouine sector belongs to the
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South-Western edge of the Tunisian trough, consisting of a transition zone between the
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central and northern Atlasic system with salt diapirs and subsiding basins (Burolet 1956; Ben
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Ayed 1993). This sector is mainly characterized by folded structures cut by the Kalaa Khasba,
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Rohia and Bou Ghanem subsiding basins (Chihi 1995).
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4. Results
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4.1. Biostratigraphic results
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4.1.1. The Bir M’Cherga section
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The Bir M’Cherga includes an 80 m thick succession of the Upper Maastrichtian, Upper
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Thanetian and Lower Ypresian units. The outcropping series of the Upper Paleocene grey
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marls (i.e. El Haria clays) overlies the grey marls and limestone beds alternations of the Abiod
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Formation (Upper Maastrichtian), all covered by a 20 m thick limestone bar of the Ypresian
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age (Bou Dabbous formation). Relative thickness and lithology allowed to distinguish three
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informal units (Fig. 2).
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Unit 1 (BM3-BM5):
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This unit is a 27m thick succession with dominate limestone intercalations bearing rich
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foraminifera association including Globotruncanita stuarti (Delapparent),
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Globotruncana aegyptica (Nakkady), Globotruncana arca Cushman),
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Globotruncana falsostuarti (Sigal), Globotruncana dupeublei (Cushman),
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Globotruncanella havanensis (Voorwijk), Rugoglobigerina rugosa (Plummer), Rosita
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patelliformis (Gandolfi), Rosita fornicata (Plummer), Rosita walfischensis (Todd),
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Hedbergella monmouthensis (Longoria et Gamper), Hedbergella holmdelensis (Olsson),
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Pseudotextularia elegans (Rzehak) Pseudotextularia nuttali (Voorwijk), Hetrohelix globulosa
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(Ehrenbeg), Planoglobulina multicamerata (Deklasz), Gublerina cuvellieri (Kikoine),
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Pseudoguembelina costulata (Cushman). To the uppermost part (BM5), we note the first
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appearance of Pseudotextularia intermedia.
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Unit 2 (BM6-BM16; 40m):
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In this unit, marly levels showed an increased thickness. The lower part (BM6-BM16), showed
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similar microfaunal association as unit “U1”, but with the appearance of new taxa within
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BM7-BM9: Contusotruncana contusa (Cushman), Planoglobulina acervilinoidess (Egger) and
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Planoglobulina riograndensis (Martin). The upper unit marly level of U2 bears: Rosita
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contuse (Cushman), Planoglobulina acervilinoides (Egger) and Planoglobulina riograndensis
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(Martin).
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Unit 3 (BM16-BM21):
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It is 13m thick succession of limestone dominating beds, bearing the same foraminifera
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association of the upper U2 unit. Gansserina gansseri (Bolli), Globtruncanita stuarti 6
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(Delapparent), Globotruncana aegyptiaca (Nakkady), Globotruncana arca (Cushman),
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Globotruncana falsostuarti (Sigae), Globotruncana dupeublei (Cushman), Globotruncanella
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havanensis (Voorwijk), Globanomalina pseudomenardii (Olsson) Trinitella scotti
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(Bronnimann), Rugoglobigerina rugosa (Plummer), Rugoglobigerina macrocephala
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(Brönnimann), Hedbergella monmouthensis (Longoria and Gamper), Hedbergella
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holmdelensis (Olsson), Contusotruncana contusa (Cushman), Rosita patelliformis (Gandolf),
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Contusotruncana fornicata (Plummer), Rosita walfischensis (Todd), Raecemiguembelina
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fructicosa (Egger), Raecemiguembelina powelli (Smith and Pessagno), Pseudotextularia
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elegans (Rzehak), Pseudotextularia nutalli (Voorwijk), Heterohelix globulosa (Ehrenberg),
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Planoglobulina multicamerata (Deklasz), Planoglobulina riograndensis (Martin),
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Pseudogumbelina palpebra (Bronnimann), Gublerina acuta (Deklasz), Gublerina cuvillieri
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(Kikoine), and Pseudoguembelina costulata (Cushman).
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Unit 4 (BM15-BM20, Fig. 2)
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After a gap of observation (2.75 m), a 16.5 m thick level (unit 4) showed greenish marls
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overlapped by a gray marl alternation and beige limestone, thickening upwards. The under the
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binocular observation showed iron oxide rich samples. Most of the observed microfauna were
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oxidized and badly preserved. The same association recognized in samples BM9 to BM16
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(i.e., below marno-limestones alternation of unit 4). However, in sample BM17, specific
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diversity as well as the number of the individuals significantly decreased.
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This association was represented by rare species of the kind Subbotina and Acarinina. We
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could determine only the species Subbotina velascoensis (Cushman), Morozovella aequa
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(Cushman and Renz), Globanomalina pseudomenardii (Olsson) and Acarinina mckannai
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(white). Towards the top (BM18, BM19 and BM20 samples), the same association of
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planktonic Foraminifera quoted in sample BM10. The foraminifer was abundant, but always
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oxidized and poorly preserved.
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4-1.2 The Tajerouine section
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In the Tajerouine area, the stratigraphic series including Upper Maastrichtian (Abiod
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formation), Upper Thanetian (El Haria formation) and Lower Ypresian (Metlaoui formation)
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levels. Two informal units can be distinguished within the out upping succession (Fig. 3):
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Unit 1 (Te8-Te28):
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It consists of pink-grey dominating marly levels with limestone intercalations bearing the
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following foraminifera assemblage: Globotruncanita stuarti (Delapparent), G. stuartiformis,
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G. aegyptiaca (Nakkady), G. arca (Cushman), G. lineiana (Orbigny), G. mairei (Banner and
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Blow), Contusotruncana fornicata (Plummer), R. patelliformis (Gandolfi), Rugoglobigerina
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rugosa (Plummer), R. hexacamerata (Broennimann), Heterohelix globulosa (Ehrenbeg),
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Pseudoguembelina costulata (Cushman), Pseudotextularia nuttali (Voorwijk).
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Unite 2 (Te2-Te6):
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The uppermost two limestone beds (20m) of the unit 1 are overlain by a thick manly level
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with iron oxide concretion and limestone intercalations. It bears the following taxa:
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Morozovella occlusa (Loeblich and Tappan), M. aequa (Cushman and Renz), Igorina albeari
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(Olsson), Subbotina velascoensis (Cushman), S. patagonica (Todd and Kniker), S.
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triangularis (Blanc), Glodanomalina Pseudomenardii (Olsson) and Acarinina wilcoxensis
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(Cushman and Ponton) (Fig. 3).
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In conclusion, the biostratigraphic study of the bir M’Cherga section showed two biozones:
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(1) Gansserina gansseri (Bolli) zone of Upper Cretaceous overlain by (2) the Glodanomalina
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Pseudomenardii (Olsson) zone of Upper Paleocene (Upper Thanetain) with a lacking Lower
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and Mid-Paleocene. The Tajerouine section showed the differentiation of two biozones
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Gansserina aegyptiaca (Bolli) zone of Upper Cretaceous over and the Glodanomalina
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Pseudomenardii (Olsson) zone of the Upper Thanetain.
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Late Paleocene was unconformably deposited above the Late Maastrichtian bels, as confirmed
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in the Bir M’Cherga and Tajerouine cross sections.
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4.2. Mineralogy analysis
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Clay mineralogical analysis of Upper Cretaceous- Paleocene successions of the two sections
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revealed the predominance of smectite, illite and kaolinite as main clay minerals associated
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with calcite, quartz and dolomite. Kaolinite was the most abundant clay mineral (40-70%) in
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the Upper Cretaceous deposits with minor amounts of smectite and illite (4 and 14%,
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respectively). Surprisingly, smectite was abundant (90%) in the Upper Cretaceous of the Bir
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M'Cherga (BM3) study site probably due to post-depositional burial linked with increased
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tectonic activity thrusting (Burollet 1956). At Bir M'Cherga and Tajeroiune sections, the
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uppermost Maastrichtian (Zone II) sediments are dominated by kaolinite (>65%), but
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gradually increasing smectite contents. Illite was
