Abstract

The Earth’s climate was marked by a pronounced warming at the onset of the Eocene Epoch, followed by successive short-lived warmings in the later part of the early Eocene. The carbon isotope (δ13C) excursions, the fingerprints of the Eocene hyperthermal events, have been established in the geological sections in India that lay across the equator in the early Eocene. The present study examines how shallow-marine foraminifera responded to the thermal events. The hyperthermal events, identified in sections of Kutch and Cambay basins corresponding to Shallow Benthic Zones (SBZs) between SBZ 5/6 to SBZ 11, have been examined for their foraminiferal assemblages, which indicate a shallow-marine environment. A significant change in the foraminiferal assemblage occurs from SBZ 5/6 to SBZ 11. The SBZ 5/6 to SBZ 10 interval (corresponding to Paleocene–Eocene Thermal Maximum, Eocene Thermal Maximum 2 and Eocene Thermal Maximum 3) is characterized by (i) low diversity and dwarfed foraminifera, (ii) rectilinear benthic foraminifera, and (iii) biserial and triserial planktic foraminifera that are known to survive in areas of high runoff, upwelling or otherwise eutrophic conditions. The stressed environments of the SBZ 5/6 to SBZ 10 appear to have ameliorated in SBZ 11 (corresponding to Early Eocene Climatic Optimum) with significant increase in abundance and diversity of foraminifera, dominance of K- strategists, and a switch from eutrophic to oligotrophic environments.

INTRODUCTION

The Paleogene successions have attracted global attention as they represent a critical interval during which the Earth’s climate regime switched from “greenhouse” to “icehouse”. The long-term cooling trend was interrupted by the short-term warming events identified as Paleocene–Eocene Thermal Maximum (PETM), Eocene Thermal Maximum 2 (ETM 2), Eocene Thermal Maximum 3 (ETM 3) and Early Eocene Climatic Optimum (EECO). The majority of the research on Eocene hyperthermal events have been reported from high latitude sites (Kelly et al., 1996, 1998; Thomas & Shackelton, 1996; Arenillas et al., 1999; Giusberti et al., 2009; Alegret et al., 2010; Stassen et al., 2012; Fig. 1). The widespread reports of greenhouse world conditions in the late Paleocene–early Eocene, however, prompted studies in low latitude sites (Jaramillo, 2002; Jaramillo et al., 2006, 2010; Zamagni et al., 2012; Khozyem et al., 2013) to determine the warmth of the tropical regions.

Foraminiferal assemblages exhibited significant changes in response to the climatic fluctuations in the Eocene. In the deep sea, the benthic extinction event recorded at the Paleocene–Eocene transition resulted in the extinction of approximately 40% of all smaller benthic foraminifera whereas in marginal seas, smaller benthic foraminifera underwent fewer turnovers (Speijer et al., 1996; Thomas, 1998). Benthic foraminifera at all depths exhibited low diversity and high dominance, and were composed of small, thin-walled or agglutinated species during the PETM (Thomas, 2007). The larger benthic foraminifera exhibited more resistance to high temperatures and the group diversified and proliferated during the early and middle Eocene, giving rise to major carbonate platforms in shallow tropical seas (Hottinger, 1998; Scheibner et al., 2005; Scheibner & Speijer, 2008; Whidden & Jones, 2012).

The Indian subcontinent was positioned along the equator during the early Eocene. The early Eocene sections in western India have recently received wide attention with recognition of evidence for hyperthermal events, including PETM, ETM 2 and EECO, using δ13C and other proxies (Clementz et al., 2011; Samanta et al., 2013; Saraswati et al., 2013). However, much less work has been done to describe the responses of the larger and smaller benthic or planktic foraminifera from these early Eocene sections of western India. The well-preserved foraminifera in the sections (Samanta, 1970; Saraswati et al., 2012, Punekar & Saraswati, 2010) provided the opportunity to investigate the paleo-environmental conditions and response of foraminiferal assemblages to the hyperthermal events in tropical India.

Geology and Stratigraphy

The Kutch basin (Fig. 2A) evolved as a pericratonic rift basin during the Jurassic and transformed to a passive-margin basin in the Cenozoic. The Cenozoic succession overlies the Deccan basalt and comprises trap-pebble conglomerate, pyroclastics and laterite at the base. These terrestrial deposits constitute the Matanomadh Formation of probable Paleocene age (Biswas, 1992). The Matanomadh Formation is overlain by a sequence of shale and limestone referred to the Naredi Formation. It is subdivided into three members: i) the Gypsiferous Shale Member consisting of glauconitic shales with intercalated gypsum layers, ii) the Assilina Limestone Member consisting of bedded limestone with yellow-grey marls rich in Assilina daviesi and Assilina spinosa, and iii) the Ferruginous Claystone Member. The Naredi Formation spans the Shallow Benthic Zones SBZ 5/6 to SBZ 11 of the early Eocene in the borehole (Fig. 3A) and SBZ 8 to SBZ 11 in the outcrop section (Fig. 3B), as previously noted by Saraswati et al. (2012). The strontium isotope data indicate that the early Eocene section of Kutch ranges in age from 54.9 ±1.5 Ma to 49.9 ± 1.5 Ma (Anwar et al., 2013). The sediments were deposited in a shallow-marine environment with water depths ranging from 10 to 30 m (Sarkar et al., 2012). The Naredi Formation is overlain unconformably by the middle Eocene Harudi Formation and the contact between the two formations is characterized by lateritized paleosol with abundant rootlets.

The Cambay rift basin lies to the south of Kutch basin (Fig. 2B). The Vastan lignite mine is a part of the Cambay rift basin. The shale and associated lignite in the mine are extensions of Cambay Shale, the source rock of hydrocarbon in the Cambay basin (Sahni et al., 2006). The Cambay Shale consists of two main lignite seams that vary in thickness from approximately 3–8 m. The sequence consists of alternating lignite bands and grey shales (Fig. 3C). The foraminifera are found in the shale part of the sequence. The upper part of the mine section is assigned to SBZ 10 on the basis of the occurrence of Nummulites burdigalensis burdigalensis (Punekar & Saraswati, 2010). Garg et al. (2008) assigned the section to the upper SBZ 7 to lower SBZ 10 based on dinoflagellates. The succession was deposited in a low-energy, shallow bay, which was flanked by marshes (Prasad et al., 2013). Stratigraphically, the Kutch basin has a more extended section of early Eocene compared with that of the Cambay basin.

The studied sections have been previously investigated for carbon isotope (δ13C) stratigraphy. The major excursions are recorded in undifferentiated SBZ5/6 (sensu Scheibner & Speijer, 2009), SBZ 8 and SBZ 10 – SBZ 11 (Samanta et al., 2013; Saraswati et al., 2013). The precise positions of the Eocene hyperthermal events are constrained elsewhere by biostratigraphy integrated with magnetostratigraphy (Agnini et al., 2009; Galeotti et al., 2010; Zachos et al., 2010; Whidden & Jones, 2012). The planktic foraminifera are few and long-ranging in the studied sections of Kutch and Cambay. We therefore follow Whidden & Jones (2012) who calibrated the Eocene hyperthermal events with Shallow Benthic Zones and accordingly referred the PETM to SBZ 5, ETM 2 to SBZ 8 and the EECO to SBZ 10–SBZ 11. The three events are recorded in the Kutch basin (Saraswati et al., 2013). In the Vastan section of Cambay basin, Samanta et al. (2013) incorrectly referred the isotopic excursion above the occurrence of Nummulites burdigalensis burdigalensis (SBZ10, Punekar & Saraswati, 2010) to ETM 2. We disagree with placing an older hyperthermal event to a younger foraminiferal zone and suggest that it best corresponds to EECO (an extended warming from SBZ 10 to SBZ 11).

MATERIALS AND METHODS

For extraction of foraminifera, shales and mudstones were disaggregated by soaking 60 g of each sample in Na2CO3 solution and gently heating for 30 minutes. The residue was washed over 44 μm (325 ASTM) and 500 μm (35 ASTM) sieves. The washed residue was then dried at 60°C in an oven. Quantitative analysis of smaller benthic, larger benthic and planktic foraminifera was performed on 19 samples from Borehole B/3/4, 15 samples from the Naredi Cliff section, and 14 samples from the Vastan lignite section. The following size fractions were studied from the residues and have been grouped as follows: i) very fine fraction (<63 μm), ii) fine fraction (63 μm–150 μm), iii) coarse fraction (150 μm–250 μm), and iv) very coarse fraction (>250 μm).

More than 300 specimens were picked and counted from each of the washed residues, upon which relative abundances of taxa were calculated. The most representative taxa were photographed using a Scanning Electron Microscope. Fisher (α) and Shannon-Weaver (H) indices were calculated using PAST analytical software (Hammer et al., 2001). The planktic foraminifera were few, owing to the shallow-marine depositional setting (paleobathymetry ~10–30 m; Sarkar et al., 2012) and, if present, were long ranging taxa and thus did not provide useful biostratigraphic control. We have therefore assigned the sections to Shallow Benthic Zones following Saraswati et al. (2012) for the Naredi Cliff and borehole and Punekar & Saraswati (2010) for the Vastan lignite mine.

For the identification of smaller benthic foraminifera, we followed Murray & Wright (1974) and Loeblich & Tappan (1987). Foraminiferal morphogroups have been widely used to determine paleo-depositional conditions based on the morphology of smaller benthic foraminifera (Nagy, 1992; Preece et al., 1999; Nigam et al., 2007; Reolid et al., 2008). We divided the smaller benthic foraminifera from our samples into the morphogroups as follows: i) Rectilinear Benthic Foraminifera (RBF): comprising genera with biserial, triserial or uniserial chamber arrangement, or ii) Rounded Benthic Foraminifera (RoBF): comprising genera with trochospiral or planispiral chamber arrangements.

RESULTS

The foraminifera are well-preserved across the section. The larger benthic foraminifera at several levels are almost glassy in appearance. Some samples in the lower part are chalky. The foraminiferal tests are not fragmented, abraded or dissolved. The tests in the uppermost limestone samples show signs of diagenesis, including infilling of chambers by sparry calcite.

The distribution and frequency of foraminiferal taxa and morphotypes in the examined sections are given in Figures 4A, 4B and 5. We report below the assemblages by biostratigraphically constrained Shallow Benthic Zones (Serra-Kiel et al., 1998). Representative taxa have been illustrated in Figure 6, and a species list is provided in Appendix 1.

Assemblage 1 (SBZ 5/6)

The foraminiferal assemblage includes planktic, larger benthic and smaller benthic representatives. The planktic foraminifera are small (<63 μm), rare and mostly comprised of biserial Chiloguembelina trinitatensis (Fig. 6.1) and triserial Jenkinsina columbiana (Fig. 6.12). The larger benthic Nummulites are abundant, although represented by relatively few species [N. fraasi (Fig 6.4), N. solitarius (Fig 6.5), and N. burdigalensis kuepperi], and confined to certain layers (Fig. 4A). Nummulites are small in size (609 ± 105 μm) and mostly represented by asexually-formed megalospheric specimens (Table 1). Cibicides alleni (Fig. 6.20), Cibicides lobatulus (Fig. 6.17), Rotalia sp. (Fig 6.3), Pararotalia curryi (Fig 6.6), and Bulimina cf. thanetensis (Fig 6.2), commonly occur in the finer fraction (63–150 μm). The relative abundance of the RBF morphotype varies from 10–40%. The Fisher alpha (α) diversity in this interval varies from 2–4 while the Shannon-Weaver (H) values vary from 1–2 (Fig. 7A). The α vs. H plot is indicative of marsh-brackish-marginal marine and normal marine-hypersaline lagoon depositional environments (Fig. 8).

Assemblage 2 (SBZ 7?)

Assemblage 2 is a poorly fossiliferous interval characterized by rare specimens (<1%) of Cibicides alleni, Pararotalia curryi (Fig. 4A), and Nummulites sp. The α and H values are <1 (Fig. 7A).

Assemblage 3 (SBZ 8)

Assemblage 3 is recorded both in the borehole and the Naredi Cliff section. The planktic foraminifera are represented by Jenkinsina columbiana and Chiloguembelina crinita (Fig. 6.16) in the very fine (<63 μm) fraction. The smaller benthic foraminifera found in the finer fraction (63–150 μm) consist of Asterigerina bartoniana (Fig. 6.13), Asterigerina abertyswythi, Pararotalia curryi, Nonionella spissa (Fig. 6.19), Florilus sp.(Fig. 6.18), Bulimina cf. thanetensis, and Rosalina sp. The coarser fraction (150–250 μm) includes taxa such as Cibicides alleni, Cibicides lobatulus, and Rotalia sp. The larger benthic foraminiferal assemblage consists of a few small-sized species (Table 1) of Nummulites [N. globulus nanus (Fig. 6.10) and N. burdigalensis kuepperi]. The RBF morphotype ranges from 10–35% of the assemblage (Fig. 4A, B). The α diversity ranges from 3–5 and H varies from 1–3 (Fig. 7A, B). The α vs. H plot is indicative of a normal marine-hypersaline lagoon-shelf depositional environment (Fig. 8).

Assemblage 4 (SBZ 9–10)

The biozones SBZ 9–SBZ 10 could not be resolved in Kutch sections but SBZ 10 is distinctly demarcated in the Vastan mine section. The larger benthic foraminifera consist of Nummulites burdigalensis burdigalensis and N. burdigalensis kuepperi. This interval in Kutch is characterized by very low diversity (α~1; H<1; Fig. 7A, B) and low abundance of foraminifera, including Asterigerina bartoniana, A. abertyswythi, Nonion applinae (Fig. 6.9), Cibicides lobatulus, C. alleni, Bulimina cf. thanetensis and Rotalia sp. found in the 63–150 μm fraction. Planktic foraminifera are few, with only Chiloguembelina crinita found in the <63 μm fraction. In Vastan lignite mine section, planktic foraminifera are absent and the assemblage is dominated by the RBF morphogroup. Praebulimina spp. (Fig. 6.7), Buliminella pupa (Fig. 6.11), Buliminella flexa, Bulimina cf. thanetensis, Nonion applinae, Florilus sp., Cibicidoides spp., Asterigerina spp., Pararotalia curryi, Rotalia sp., Rosalina sp. (Fig. 6.8), and rare specimens of Fursenkoina sp. are also found in the 63–150 μm fraction. The RBF morphogroup comprises 50–70% of the total assemblage (Fig. 5). The assemblage is characterized by low diversity (α = 1–3; H = 1–2; Fig. 7C). The α vs. H plot (Fig. 8) is indicative of normal marine-hypersaline lagoonal depositional environments.

Assemblage 5 (SBZ 11)

Foraminifera indicating SBZ11 are present only in Kutch sections. The foraminiferal assemblage is characterized by much higher diversity (α = 10–11, H = 3.5–4), the highest that we recorded (Fig. 7A, B). The assemblage is distinctly dominated by larger benthic foraminifera, Nummulites burdigalensis cantabricus (Fig 6.14), Assilina spp. (Fig. 6.15), Lockhartia spp., and Operculina spp., all of which attained large size (see Table 1 for N. burdiaglensis lineage) and are represented by both microspheric and megalospheric generations. The smaller benthic foraminifera include C. alleni, C. lobatulus, Quinqueloculina contorta (Fig. 6.21), Spiroloculina sp. (Fig. 6.23), and Rotalia sp. found in the 150–250 μm fraction. Other smaller benthics, including Lagena sp. (Fig. 6.22), Sagrina spp., Fursenkoina sp., Nonion applinae, Pijpersia coronaeformis (Fig. 6.24), Bulimina cf. thanetensis, Praebulimina spp., Nonionella spissa, and Florilus sp., were found in both fine and coarse fractions (63–250 μm). The RBF morphogroup comprised only 10–20%, markedly lower than the other assemblages (Fig. 7A, B). The α vs. H plot is indicative of a shelf depositional environment (Fig. 8).

DISCUSSION

Responses to Paleoclimate

Organisms respond differently to climate change. The global warming at the close of the Paleocene led to extinction of 30–50% of the benthic foraminiferal species in the deep sea (Thomas & Shackelton, 1996). On the contrary, there was a rapid increase in diversity, shell size and adult dimorphism in the shallow-dwelling, larger benthic foraminifera (Hottinger, 1998). The diversification was so intense that these foraminifera, along with corals, became the major producers of carbonates in several parts of the world, including India. A synthesis of reports of early Paleogene carbonate platforms on the margin of the Tethys has recognized three stages of their development (Schiebner & Speijer, 2008). Stage 1 (late Paleocene, SBZ 3) was dominated by coral-algal reefs in mid paleolatitudes and by larger foraminifera in low paleolatitudes. Stage 2 (late Paleocene, SBZ 4) also was dominated by coral-algal reefs in mid paleolatitudes and by the larger foraminifera, Ranikothalia, Miscellanea and Assilina, in low paleolatitudes. Stage 3 commenced with a “Larger foraminifera turnover” at the Paleocene–Eocene boundary (Scheibner & Speijer, 2008) and was dominated by species of Nummulites, Alveolina and Orbitolites in both low and mid paleolatitudes. Stages 1 and 2 are not found in the Kutch basin. The earliest marine record is of early Eocene age. The late Paleocene is also absent in offshore Kutch, as the lowermost sediments overlying the Deccan basalt are referred to the N. deserti-Miscellanea miscella assemblage (Mehrotra, 1989).

India lay at the equator (Chatterjee et al., 2013) when the Earth was passing through a phase of major warming and the enormous release of methane during the PETM. The carbonate platforms of this time, which developed at several places on the margins of the Indian craton, had larger benthic foraminifera as major constituents. The present-day representatives of these foraminifera are known to thrive in clear, warm waters of oligotrophic seas and require a minimum temperature of 18°C for reproduction (Nemkov, 1960). The palynofloral records of the northern Himalaya (Mathur, 1984), Barmer (Tripathi et al., 2009), Kutch (Saxena & Ranhotra, 2009) and Vastan (Mandal & Guleria, 2006) further suggest hot and humid climates in late Paleocene–early Eocene. The biomarkers of the resins of Vastan are indicative of Dipteocarpacea vegetation in the early Eocene, which is common in the tropical rainforests of Asia (Dutta et al., 2011). The sea-surface temperature is believed to have been consistently high in lower latitudes during the early Paleogene. The δ18O and TEX86 index from Tanzania indicate temperatures in excess of 30°C (Pearson et al., 2006). The seawater temperature estimated by δ18O of Nummulites from Kutch is about 32°C in the Early Eocene (Saraswati et al., 1993). The geological records in India unequivocally suggest prevalence of a warm and humid climate, presence of rainforests and mangroves, and seawater temperatures above 30°C in the early Eocene.

The Kutch and Vastan sections together provide a complete record of early Eocene hyperthermal events in shallow-marine to marginal-marine environments, revealing how foraminiferal assemblages responded through the warming events. The ecological characteristics of foraminifera through this interval are discussed below.

Responses of Foraminiferal Populations and Assemblages

The “Lilliput effect” or decrease in size is found in many organisms (Urbanek, 1993) associated with high-stress environments such as greenhouse warming (Abramovich & Keller, 2003), volcanism (Keller, 2005; Keller et al, 2007), restricted basins, shallow marginal settings and also aftermaths of extinction events (Twitchett, 1999, 2006; Twitchett et al., 2001). Smaller organisms tend to have early sexual maturity and faster reproductive rates, which maximizes their chance for survival in highly stressed environments (MacLeod, 1990; MacLeod et al., 2000). Dwarfing affects both K- and r-strategist species (Abramovich & Keller, 2003). Dwarfism is observed in C. alleni, C. lobatulus and Rotalia sp. from the SBZ 5/6 of Kutch in which the PETM is recorded. The SBZ 11 interval is marked with a significant increase in size of specimens. In larger benthics, the N. burdigalensis lineage shows a 2.5 times increase in diameter of A-forms between SBZ 5/6 and SBZ 11 (Table 1). Overall foraminiferal species increased in size by the end of SBZ 11 (EECO), indicating return of favorable conditions for the growth of foraminifera.

Diversity reduction is another response to stressed environments (Abramovich et al., 2003). The α-diversity of foraminifera during the biozones SBZ 5/6 to SBZ 10, corresponding to thermal events PETM, ETM 2 and ETM 3(?), remained <4, while H values were <2.5. Diversity increased considerably in the SBZ 11, reaching to α values of 11 and H values of 3.5–4, indicating favorable environmental conditions for diversification of the foraminiferal community. Moreover, for every biozone corresponding to a hyperthermal event, diversity declined considerably, approaching zero (Fig. 7A–C).

The triserial and biserial planktic foraminifera, Jenkinsina and Chiloguembelina, are the generalist/opportunist eutrophic-index species, which are associated with extreme climatic conditions such as Cretaceous oceanic anoxic events (Nederbragt et al., 1998), the KT boundary (Koutsoukos, 1994; Keller & Pardo, 2004; Pardo & Keller, 2008), the PETM, and the Middle Eocene Climatic Optimum (Luciani et al., 2007, 2010; D’haenens et al., 2012), during which they are found to increase in relative abundance. Both genera occur abundantly in SBZ 5/6 and SBZ 8 (PETM and ETM 2). Jenkinsina is morphologically comparable to recent triserial planktic Galitellia, which live in unstable environments with possibly high runoff or upwelling conditions (e.g., Kroon & Nederbragt, 1990; Ghosh et al., 2008; Kimoto et al., 2009). The biserial forms are considered to be tolerant of low oxygen conditions (Kroon & Nederbragt, 1990; Nederbragt, 1991). The moderate abundance of their representatives Chiloguembelina trinitatensis (~40%) in SBZ 5/6 and Jenkinsina columbiana (~20%) in SBZ 8 is further indicative of low oxygen, meso-eutrophic conditions during the PETM and ETM 2.

The Rectilinear Benthic Foraminifera (RBF) morphogroup varies from 10–40% in SBZ 5/6, and from 10–35% in SBZ 8. The RBF increase to ~50–70% during SBZ 10, decreasing thereafter to 10–20% in SBZ 11. The RBF are tolerant of low oxygen conditions and constitute more than 40% of the total foraminiferal assemblage in the oxygen-minimum zone of the Arabian Sea (Nigam et al., 2007). The maximum abundance of RBF in Kutch and Cambay basins are recorded in SBZ 10. These low oxygen tolerant taxa declined markedly in SBZ 11.

The larger benthic foraminifera are considered to be K-strategists, that is, they are characterized by a long individual life and low reproductive potential that are advantageous in stable and oligotrophic environments where organisms compete by specialization and habitat partitioning (Hallock et al., 1991; Hottinger, 1998). The abundance and diversity of larger foraminifera increased markedly during the EECO (Assilina spp., Lockhartia spp., Nummulites spp., Operculina spp.) and they dominate the assemblage in SBZ 11 compared to SBZ 10, SBZ 8, or SBZ 5/6, suggesting environmental stability and low nutrient flux during the SBZ 11. The SBZ 5/6 and SBZ 8 were dominated by eutrophic-indicator, biserial benthics such as Bulimina sp., Praebulimina spp., Brizalina sp., and Buliminella spp., which are opportunists (Jones & Charnock, 1985; Bernhard, 1986; Nagy, 1992; Sen Gupta, 1993; Preece et al., 1999; Reolid et al., 2008). A switch from opportunist-dominated to K-strategist-dominated foraminiferal assemblages is typically recorded from the SBZ 5/6 to SBZ 11.

CONCLUSIONS

  1. The SBZ 5/6 assemblage, which corresponds to the PETM, is characterized by a low diversity assemblage of dwarfed foraminifera. The opportunistic, triserial-planktic foraminifera and biserial-benthic foraminifera occurred in moderate to high abundance, indicative of eutrophic conditions.

  2. The SBZ 8 assemblage, corresponding to ETM 2, had relatively higher abundance and diversity of foraminifera compared with SBZ 5/6. The species of Nummulites are comparatively larger in size but other characteristics of the foraminiferal assemblage remain similar to those of the SBZ 5/6.

  3. The interval between SBZ 5/6 and SBZ 11 has several barren to poorly fossiliferous levels, often containing solitary specimens of Nummulites spp., Pararotalia sp., or Rotalia sp., possibly due to repeatedly stressful conditions. The high abundance of RBF in some intervals suggests pulses of low oxygen conditions.

  4. The abundance and diversity of foraminifera increased significantly in SBZ 11, corresponding with EECO. The nummulitids attained normal size. The population of K-strategists increased and they became dominant producers of early Eocene carbonates in western India. The SBZ 5/6 to SBZ 11 marked a switch from eutrophic to oligotrophic shelf environments.

ACKNOWLEDGEMENTS

We are thankful to University Grants Commission for providing a research fellowship to SK to carry out this work. We thank Dr. N. L. Sharma, Director, GMRDS (Gandhinagar), for providing borehole samples of Kutch. We gratefully acknowledge Dr. Pamela Hallock Muller for the initial reading of the manuscript, and the two anonymous reviewers for their constructive suggestions to improve the text.

APPENDIX 1

List of species from early Eocene sections of the study area.

Planktics

Chiloguembelina trinitatensis (Cushman and Renz)

Chiloguembelina crinita (Glaessner)

Jenkinsina columbiana (Howe)

Turborotalita sp. Blow and Banner

Smaller Benthics

Rotalia sp. Lamarck

Rosalina spp. d’Orbigny

Quinqueloculina contorta d’Orbigny

Spiroloculina sp. d’Orbigny

Bulimina cf thanetensis Cushman and Parker

Brizalina oligocaenica (Spandel)

Buliminella pupa Cushman and Parker

Fursenkoina sp. Lobelich and Tappan

Sagrina selesyensis (Heron-Allen and Earland)

Praebulimina sp. Hofker

Lagena sp. Walker and Jacob

Asterigerina abertyswythi Haynes

Asterigerina bartoniana (Ten Dam)

Nonionella spissa Cushman

Florilus sp. de Montfort

Nonion applinae Howe and Wallace

Pijpersia coroneformis (Pijpers)

Pararotalia curryi Lobelich and Tappan

Cibicides lobatulus (Walker and Jacob)

Cibicides succedens Brotzen

Cibicides alleni (Plummer)

Buliminella flexa Cushman and Parker

Pararotalia spinigera (Le Calvez)

Asterigerina spp. d’Orbigny

Cibicidoides sp. Thalmann

Valvulineria scrobiculata (Schwager)

Gyroidinoides sp. Brotzen

Larger Benthics

Assilina daviesi de Cizancourt

Assilina spinosa Davies and Pinfold

Assilina spp. d’Orbigny

Lockhartia spp. Davies

Nummulites fraasi de la Harpe

Nummulites solitarius (Schaub)

Nummulites globulus nanus Schaub

Nummulites burdigalensis burdigalensis (Schaub)

Nummulites burdigalensis cantabricus (Schaub)

Nummulites burdigalensis kuepperi (Schaub)