Cenomanian-Turonian sea-level transgression and OAE2 deposition in the Western Narmada Basin, India
Introduction
The Narmada Basin in India is an intracratonic rift basin of intense interest because of its tectonic history and northward journey after the breakup of Gondwana in the Early Cretaceous ~130 Ma (Tandon, 2000; Chatterjee et al., 2013; Kumari et al., 2020). Madagascar separated from India during the Turonian to Santonian transition and from the Seychelles during the Campanian to early Maastrichtian. Highlights of this journey are recorded in the Bagh Group exposed in disconnected outcrops along the edges of the Deccan basalt, and overlie Precambrian rocks from Madhya Pradesh to Gujarat (Tandon, 2000; Tripathi, 2006; Tripathi, 2005; Kumari et al., 2020) (Fig. 1).
Sediment deposition in the Narmada Basin occurred in a tectonic graben that was largely controlled by uplift, block faulting, volcanic activity, erosion and sea level transgressions (Biswas, 1987; Kumar et al., 1999; Tandon, 2000; Tripathi, 2006; Bansal et al., 2020; review in Kumari et al., 2020). Clues to this history can be found in the Late Cretaceous sediments roughly parallel to the present course of the Narmada River. In both eastern and western parts of the Narmada Basin, the Nimar Sandstone overlies the Archean crystalline basement rocks in a westerly sloping basin (Tripathi, 2006). However, the overlying sedimentary sequences vary.
In the eastern (upper) Narmada Basin of Madhya Pradesh, the fossiliferous marine transgression of the Bagh Group consists of Nodular Limestone, Chirakhan marl and Coralline Limestone topped by glauconite and overlain by the Maastrichtian Lameta Formation (Chiplonkar, 1982; Bansal et al., 2020). The eastern Bagh Group has been extensively studied based on ammonoids, ostracods, echinoids, bryozoan, marine algae and planktic foraminifera with ages attributed to the Turonian-Coniacian (Jain, 1975; Chiplonkar, 1982; Nayak, 1987; Chaudhary and Nagori, 2019). A recent study of ammonites and inoceramids in the Nodular Limestone revealed early, middle and late Turonian deposition (Kumar et al., 2018). These deposits mark the eastward-reach of a sea-level transgression during the Turonian (Tandon, 2000; Tripathi, 2006; Bansal et al., 2020; Kumari et al., 2020) and unconformably overlie the predominantly continental Nimar Sandstone.
In the western Narmada Basin of Gujarat, the Turonian-Coniacian limestone units of the Bagh Group from Madhya Pradesh are not present, likely because of tectonic activity, uplift, erosion and non-deposition (Tripathi, 2006). Instead, the estuarine facies of the Nimar Sandstone underlie in ascending order, a micritic sandstone, oyster beds and limestone with oysters, revealing the first major sea-level transgression into the western Narmada Basin (Tandon, 2000; Tripathi, 2006). The depositional age was determined as Late Cenomanian to Early Turonian based on ostracods and calcareous algae (Kundal and Sanganwar, 1998; Chaudhary et al., 2017a).
The focus of this study is the first sea-level transgression into the western Narmada Basin in Gujarat during the late Cenomanian that originated central India's Narmada Seaway, which reached about 800 km across India by the end of the Maastrichtian (Keller et al., 2009). We explore whether this sea-level transgression could be linked to the global transgression that occurred during the late Cenomanian-early Turonian Oceanic Anoxic Event 2 (OAE2) based on two outcrops in Gujarat near the villages of Bilthana and Bhundmariya (Fig. 1A, B). We focus on four objectives: (1) improve biostratigraphy and age control; (2) determine the paleoenvironment and onset of the sea-level transgression; (3) identify the link between the sea-level transgression and the OAE2; and (4) test the potential link between volcanism, LIPs, and Hg toxicity during this time.
Our investigations focus on biostratigraphy of planktic foraminifera and ostracods for age control, the nature of sediment deposition and characteristic fossil life for paleoenvironmental reconstructions, carbon isotopes for the identification of the OAE2, oxygen isotopes for paleoclimate and fresh water influx reconstructions, and mercury concentrations in sediments for assessing the potential influence (toxicity, warming) of large volcanic eruptions.
Section snippets
Materials and methods
We analyzed Bhundmariya and Bilthana localities from Gujarat in the western Narmada Basin. The Bilthana section is located near the village of Bilthana, along the Men River (N 21° 57′; E 73° 39′) (Fig. 1A, C). The Bhundmariya section, is located near the village of Bhundmariya, also along the Men River (N 21° 59′; E 73° 59′) (Fig. 1B, C). In both sections, the Nimar Sandstone followed by the Micritic Sandstone mark the base of the Bagh Group and disconformably overlie crystalline Archaean
Age and biostratigraphy
The Nimar and Micritic Sandstones are the oldest sediments overlying the Archean crystalline rocks in this area and the age was previously attributed to the Cenomanian based on ostracods and calcareous algae (Kundal and Sanganwar, 1998; Chaudhary et al., 2019). Planktic foraminifera are rare to few, small, long-ranging and stress tolerant species but not age diagnostic (Muricohedbergella, Planoheterohelix, Heterohelix). Benthic foraminifera are generally long-ranging and not useful age
Carbon and oxygen stable isotopes
We analyze carbon and oxygen stable isotopes of the Bhundmariya and Bilthana sections from Gujarat (Fig. 4, Fig. 5) to evaluate nutrient and salinity trends in shallow neritic environments during the OAE2. We compare the Gujarat δ13C record with similar shallow marine sequences in the Tethys Ocean from the Sinai, Egypt, to Morocco and Pueblo, Colorado, USA Western Interior Seaway (Fig. 6). The OAE2 has a 2‰ to 3‰ positive δ13C excursion, prolonged plateau and gradual decrease across the
Mercury
Mercury anomalies in sediments worldwide have been identified as potential proxy for Large Igneous Province (LIP) volcanism associated with all five major mass extinctions in Earth's history (e.g., Grasby et al., 2016; Gong et al., 2017; Jones et al., 2017; Percival et al., 2017; Thibodeau and Bergquist, 2017; Bond and Grasby, 2020; review in Grasby et al., 2019; Keller et al., 2020). Similarly, three submarine LIPs have been identified as active during the Cretaceous Oceanic Anoxic Events
Discussion
This study began with a single objective: a routine biostratigraphic age analysis based on planktic foraminifera of the Bilthana section in Gujarat. It turned out to be a high-stress nearly monospecific assemblage in an estuarine to subtidal environment of late Cenomanian age. We confirmed this observation by collecting and analyzing a second locality, Bhundmariya located ~25 km to the east (Fig. 1C). Results showed deposition at Bhundmariya occurred in slightly deeper subtidal waters with
Conclusions
- (1)
We report the first evidence of the late Cenomanian-early Turonian OAE2 in the western Narmada Basin associated with the largest sea-level transgression of the Cretaceous that initiated the western Narmada Seaway, which by the end of the Turonian reached from Gujarat through Madhya Pradesh. At times this seaway may have connected to the Godavari Seaway via the Narmada-Tpati rift forming a Trans-India Seaway to Rajahmundry.
- (2)
The characteristic OAE2 gradual onset of the δ13C excursion began with
Author Contributions
Gerta Keller: Conceptualization; Data curation; Formal analysis; Funding acquisition; Investigation; Methodology; Project administration; Resources; Supervision; Validation; Visualization; Writing - original draft; Writing - review & editing. Madan Nagori: Funding acquisition; Investigation; Methodology; Resources; Writing - review & editing. Maya Chaudhary: Investigation; Methodology; Resources; Writing - review & editing. Nallapa A. Reddy: Investigation; Methodology; Resources; Writing -
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
We thank the four anonymous reviewers for their very helpful comments that helped improve this study. We thank Professor Jahnavi Punekar (Department of Earth Sciences, IIT Bombay) for discussions and her graduate student, Mr. Sooraj C.P., for processing samples. Partial funding for analytical studies was provided by Princeton University through the Geosciences Department's Tuttle and Scott funds. MLN and MC are thankful to the coordinator (SAP) in the Department of Geology, Mohanlal Sukhadia
References (88)
Regional tectonic framework structure and evolution of western marginal basins of India
Tectonophysics
(1987)- et al.
The expression of the Cenomanian–Turonian oceanic anoxic event in Tibet
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2013) - et al.
High-resolution stratigraphy of the Cenomanian-Turonian boundary interval at Pueblo (USA) and Wadi Bahloul (Tunisia): stable isotope and bio-events correlation
Geobios
(2006) - et al.
The longest voyage: Tectonic, magmatic, and paleoclimatic evolution of the Indian plate during its northward flight from Gondwana to Asia
Gondwana Res.
(2013) - et al.
On the ages of flood basalt events
Compt. Rendus Geosci.
(2003) - et al.
Stratigraphy of the Cenomanian-Turonian Oceanic Anoxic Event OAE2 in shallow shelf sequences of NE Egypt
Cretac. Res.
(2011) - et al.
Palaeoclimate and palaeovegetation in Central India during the Upper cretaceous based on stable isotopic composition of the palaeosol carbonates
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1995) - et al.
Mercury as a proxy for volcanic emissions in the geologic record
Earth Sci. Rev.
(2019) Cretaceous eustasy revisited
Glob. Planet. Chang.
(2014)Biotic effects of volcanism and impacts
Earth Planet. Sci. Lett.
(2003)