Palaeocene Eocene Transition Research Articles

Dinoflagellate cysts from the Shillong Plateau, Meghalaya (India): Palynological signature during the late Palaeocene–early Eocene Transition

AbstractThe paper presents a new section of the late Palaeocene‐early Eocene, palynological assemblages and stable carbon isotopes from the Lakadong sandstone member of the East Khasi Hills of Meghalaya (India). The Palaeocene‐Eocene transition (PET) is marked by stratigraphic markers of dinoflagellate cysts (taxa of Apectodinium augustum, now Axiodinium augustum) and negative carbon isotope excursion. The palynofloral assemblage indicates the sequence represents warm, humid tropical to subtropical conditions with heavy rainfall. The depositional environment of the Lakadong Sandstone Member is interpreted to be neritic. The new insights of this study in this section suggest the PET with the occurrence of Apectodinium acme consisting of A. augustum at CS5‐15a.

Clay mineralogical evidence of near-equatorial Palaeocene–Eocene Thermal Maximum in Barmer Basin, India

Abstract The Palaeocene–Eocene Thermal Maximum (PETM) was a global extreme climatic event, but it is relatively unknown from lower latitudes or equatorial regions in comparison to mid- and high latitudes. The present study provides the first clay mineralogical evidence of the PETM and subsequent hyperthermal events in a near-equatorial region represented by the Akli Formation in the Barmer Basin, India. The 32 m-thick succession of the Akli Formation shows abrupt changes in smectite and kaolin abundances preceding, during and succeeding the PETM event. Within the studied section, the kaolin content increases from 5–8% pre-PETM to 30–35% during the PETM, and then again decreases to 5–6% during the post-PETM period. The smectite, however, is marked by a corresponding decrease and its transformation into kaolin in acid weathering conditions. The transformation of the smectite is first marked by hydroxy interlayering and then transformation into kaolin during the PETM. The transformation of smectite into kaolin also resulted in extensive precipitation of iron oxide in sediments. The clay mineralogical changes in the Palaeocene–Eocene transition sediments of the Akli Formation were caused by 3–5°C warming and a 25–50% increase in rainfall during the hyperthermal events. Unusually high charcoal (~20%) fragments during the Palaeocene–Eocene transition also suggest warming and widespread biomass burning during the PETM in the lower latitudes.

A new Palaeogene elasmobranch fauna (Tebessa region, eastern Algeria) and the importance of Algerian-Tunisian phosphates for the North African fossil record

During the Palaeocene-Eocene transition, the southern Tethys margin is characterized by several African phosphate deposits with many fossil teeth of elasmobranchs. Contrary to the rich Moroccan fossil record, fossil elasmobranchs from the area that includes today the Algerian-Tunisian border (e.g. Metlaoui-Gafsa-Onk Basin) have received few attentation since the last century of exploration. New collecting in the vicinity of Tebessa, Eastern Algeria (Jebel El Onk mine) allowed to report a new elasmobranch fauna in the so-called “Upper Thanetian” level. It consists of 28 taxa including a new species of a galeocerdid, Physogaleus onkensis sp. nov., which is characterized by a possible crushing adaptability of their teeth. The majority of the reported species are known in coeval phosphate levels enabling preliminary conclusions about the depositional time and correlations to the related faunas of the region. The faunal from the Jebel El Onk mine is considered as late Thanetian–early Ypresian in age.

The origin of modern patterns of continental diversity in Mauritiinae palms: the Neotropical museum and the Afrotropical graveyard.

While the latitudinal diversity gradient has received much attention, biodiversity and species richness also vary between continents across similar latitudes. Fossil information can be used to understand the evolutionary mechanisms that generated such variation between continents of similar latitudes. We integrated fossil data into a phylogenetic analysis of the Mauritiinae palms, whose extant diversity is restricted to the Neotropics, but extended across Africa and India during most of the Cenozoic. Mauritiinae diverged from its sister lineage Raphiinae ca 106 Ma. Using ancestral state estimation and a lineage through time analysis, we found that diversity arose globally during the late Cretaceous and Palaeocene across South America, Africa and India. The Palaeocene-Eocene transition (ca 56 Ma) marked the end of global Mauritiinae expansion, and the beginning of their decline in both Africa and India. Mauritiinae disappeared from the Indian subcontinent and Africa at the end of the Eocene and the Miocene, respectively. By contrast, Neotropical diversity steadily increased over the last 80 Myr. Taken together, our results suggest that the Neotropics functioned as a continental-scale refuge for Mauritiinae palms, where lineages survived and diversified while global climatic changes that drastically reduced rainforests led to their demise on other continents.

3D seismic geomorphology of Early Cenozoic incised channels, Gippsland Basin, SE Australia: Evidence for submarine origin

The Latrobe Group in the Gippsland Basin consists of well-developed, stacked shoreface and coastal plain deposits, cut by large, incised channel systems up to 500 m deep. These large channels are conspicuous on seismic intersections and have previously been interpreted as the result of fluvial incision associated with basin inversion/compressional tectonics. Here we have used 3D seismic, well log, and core to re-evaluate the origin of these channel systems. We interpret three major phases of channel incision-infilling; Tuna Channel 1, Tuna Channel 2 and the Marlin Channel. Biostratigraphic data shows that the channels range in age from the Palaeocene-Eocene transition to the Late Eocene. These ages indicate channel formation occurred prior to the onset of compressional tectonics in the Gippsland Basin, which began at the Eocene-Oligocene transition.Correlation of these channels with coeval palaeoshoreface systems reveals that the channels are located seaward of, and in close proximity to these shorelines. Well data indicates that the channel fill sediments are of marine origin, consisting of glauconite, dinoflagellates, foraminifera, and marine macro fossils. We do not observe evidence for a regional unconformity which would correlate with over 500 m of subaerial channel incision. These channels are therefore interpreted as submarine canyons, rather than channels of fluvial origin. They are interpreted as shelf-incising, with canyon heads located close to coeval palaeoshorelines where they received sediment via longshore/littoral processes. The erroneous identification of submarine canyons as incised valleys in sedimentary basins has significant implications for tectonic and eustatic histories globally.

Calcareous nannofossil bioevents at the Paleocene/Eocene boundary in Kharga Oasis, Western Desert of Egypt

Two upper Palaeocene – lower Eocene stratigraphic sequences at the Kharga Oasis (Umm El Ghanayim and Naqb Assiut sections) were studied biostratigraphically on the basis of their calcareous nannofossil content. The investigated interval includes the upper part of the Tarawan Formation, the Tarawan Chalk, and the Esna formations. A total number of sixty-seven different taxa have been identified. The lowest occurrence (LO) of Discoaster araneus was used to place the base of the NP9b Subzone (base of Eocene) at the Gabal Umm El Ghanayim section. The lowest occurrences (LOs) of Rhomboaster bitrifida, Discoaster araneus and D. anartios are used to define the NP9a/NP9b subzonal boundary at the Gabal Naqb Assiut section. In this section,the P/E boundary is marked by a minor lithologic hiatus as indicated by the absence of the basal part of the Dababiya Member.At the studied two sections, a major turnover in calcareous nannofossil assemblages across the P/E transition was documented. The abundance of warm water Ericsonia subpertusa, Fasculithusspp., Coccolithus eopelagicus, Discoaster spp., Rhomboaster bitrifida and Tribrachiatus bramlettei characterize the Palaeocene-Eocene transition and suggest global warming and the Palaeocene – Eocene Thermal Maximum (PETM).

Microfacies analysis of larger benthic foraminifera-dominated Middle Eocene carbonates: a palaeoenvironmental case study from Meghalaya, N-E India (Eastern Tethys)

Larger benthic foraminifera (LBF) show significant abundance and diversity in the Palaeogene carbonate sediments of Meghalaya, N-E India, but have previously received less attention from the palaeoenvironmental perspective. LBF are important contributors to recent as well as fossil shallow marine, tropical carbonate settings. They find wide application in biostratigraphy and palaeoenvironmental reconstructions. The larger foraminiferal turnover (LFT) during the Palaeocene-Eocene transition is very important with respect to their evolution in several parts of the world including the Eastern Tethys. The present microfacies analysis documents the status of LBF in the Middle Eocene sediments from the Prang Formation of the Sylhet Limestone Group in Meghalaya, N-E India. Five major facies types (MFTs)—miliolid grainstone-packstones, alveolinid-rotaliid grainstone-packstones, nummulitid-alveolinid grainstone-packstones, coralline algal-nummulitid packstone-wackestones and coralline algal wackestones have been recorded in the current study. Evaluation of the palaeoenvironmental parameters aids in understanding the seascape of this Eastern Tethyan domain. It is suggested that an oligotrophic nutrient regime supported the rapid evolution and dominance of the LBF. Most notable is the prolific augmentation in Alveolina and Nummulites populations. High surface water temperatures during the Late Palaeocene-Early Eocene global warming episode possibly persisted to a certain level during the Middle Eocene and continued to favour the larger foraminifera as the major carbonate producers instead of the vulnerable corals.

Palaeocene-Eocene evolution of beta diversity among ungulate mammals in North America

Aim The Palaeocene–late Eocene transition in North America marks a critical interval in the evolution and diversification of land mammals, including adaptive radiation in the Palaeocene, and repeated waves of immigration over habitat bridges at the Palaeocene–Eocene boundary. We investigate the fossil record of ungulate mammals over this period to understand the effects of immigration and faunal exchange on local (alpha), regional (gamma) and between-site (beta) diversity. Location North America. Methods We use Palaeocene and Eocene records of North American ungulate mammals taken from the Paleobiology Database (PBDB), and calculate beta diversity among families and genera within the seven stages of the Cenozoic. We reconstruct geographic ranges sizes for studied taxa, and test trends in these ranges against null models used to control for sampling biases. Finally, we use Mantel tests to quantify the relationship between geographic distance and faunal dissimilarity within each time slice, in order to visualize changes in the spatial complexity of mammal communities. Results Gamma diversity increases over the studied interval, with varying contributions from alpha and beta diversity. Beta diversity increases from the Palaeocene to Eocene, reflected in decreasing range size and increased correlation between reconstructed distance and faunal similarity. Increase in beta diversity over the Palaeocene–Eocene transition is driven by smaller geographic ranges among putatively invasive ‘immigrant’ and secondarily endemic taxa; range contraction among these groups in the middle–late Eocene leads to a Bartonian peak in beta diversity. Main conclusions High gamma diversity in the Eocene was driven by high beta diversity rather than alpha diversity, indicating that range contraction in both immigrant and secondarily endemic taxa restructured the spatial organization of mammal communities. These parallel trends suggest that factors such as tectonic uplift or climate change were responsible, as opposed to ecological differences. Increase in beta diversity over the Palaeocene–Eocene boundary suggests that over longer time-scales, mass immigration events can lead to greater overall richness and greater heterogeneity, rather than homogeneity, within regional assemblages.

A new terrestrial palynoflora from the Palaeocene/Eocene boundary in the northwestern Tethyan realm (St. Pankraz, Austria)

Inner neritic marly claystone of the South-Helvetic thrust unit (Eastern Alps) at St. Pankraz (Salzburg, Austria) yields high percentages of the dinoflagellate genus Apectodinium including the species Apectodinium augustum. The range of this species is almost exclusively restricted to the negative carbon isotope excursion (CIE) at the base of the Eocene. The associated terrestrial palynoflora consists of common Normapolles s.l. and post- Normapolles types with accessory mesothermal and megathermal families such as Anacardiaceae, Arecaceae, Euphorbiaceae s.l., Hamamelidaceae, Icacinaceae, Malvaceae (subfamilies of Helicteroideae, Sterculoideae, Tiloideae), Rutaceae, Sapotaceae and Schizaeales. This composition is similar to the Upper Thanetian palynological record of the same sedimentary succession. It suggests a warm and humid climate in the northwestern Tethyan realm during the Late Thanetian and Early Ypresian. Three new taxa probably have their lowermost occurrence in the basal Eocene. However, neither a major floral change nor the establishment of fully tropical conditions are indicated for the Palaeocene–Eocene transition.

COMPARISONS BETWEEN PALAEOCENE–EOCENE PARATROPICAL SWAMP AND MARGINAL MARINE POLLEN FLORAS FROM ALABAMA AND MISSISSIPPI, USA

Abstract: Climate warming at the Palaeocene/Eocene boundary (c. 55.8 Ma) had significant permanent affects on paratropical and warm‐adapted vegetation types. Pollen and spore records which document vegetation turnover from the eastern US Gulf Coast have all been taken from sediments of marginal marine depositional environments. Pollen and spores (sporomorphs) are preserved excellently in these marginal marine depositional environments but these assemblages contain grains transported from many different vegetation types and over huge geographic distances. Currently it is unclear whether the turnover from important paratropical areas like the US Gulf Coast is a reflection on actual vegetation change in the local region or from source areas far away in the continental interior. Sporomorph data from 20 former swamps (lignites) from the Nanafalia, Tuscahoma and Hatchetigbee formations in Mississippi and Alabama, USA, are used to test the fidelity of the marine sporomorph record across the Palaeocene–Eocene transition. Data show that extinction is noted in the swamp record (≥7 per cent of Palaeocene taxa) and that swamps were susceptible to immigration in the Early Eocene with the first occurrences of Brosipollis spp. (Burseraceae), Dicolpopollis spp. (Palmae), Nuxpollenites psilatus (Loranthaceae) and Platycarya spp. (Juglandaceae). Swamps have higher within‐sample diversity in the Eocene but higher among‐sample diversity in latest Palaeocene–earliest Eocene samples, which parallels exactly diversity trends estimated from marine sporomorph assemblages. Palms also increase in abundance in the Eocene. The swamp data demonstrate that the flora growing in these ancient paratropical forests was diverse (c. 120 taxonomic groups) but incorporated an unusual admixture of plants with modern tropical affinities together with those that now live in modern temperate to subtropical North America.

Thermal modelling of magmatic intrusions in the Gjallar Ridge, Norwegian Sea: implications for vitrinite reflectance and hydrocarbon maturation

ABSTRACTExtensive magmatic activity took place in the Vøring Basin, offshore Norway, related to the Early Cenozoic rifting. The break‐up of the North‐Atlantic at the Palaeocene–Eocene transition induced strong volcanism. There are numerous magmatic sills below 3 km depth in the area. They are predominantly layer parallel and thin compared with their lateral extent. Igneous intrusions, sills and dykes affected the temperature history, and thus need to be taken into account in petroleum prospect analysis. We have calculated the temperature and maturity effects in the sedimentary layers in the Gjallar area associated with the emplacement of single sill and sill complexes. A 120‐m‐thick sill produces a theoretical vitrinite reflectance (%R0) 0.8% higher than normal at a distance of 100 m from the sill. Vitrinite reflectance changes caused by a swarm of seven sills varying from 8 to 80 m in thickness were calculated. It is shown that the calculated thermal profile can account for the observed shift in vitrinite reflectance in the well. A two‐dimensional section crossing the Gjallar Ridge, consisting of numerous magmatic intrusions, is also modelled. The modelled geological development and temperature history over the profile show that there are significant maturation effects in the interval under investigation. Based on this work, the sill swarm observed in the area could more than double the fraction of the kerogen that has been transformed to petroleum at the (present) depth of 4 km.

An Ailuravine Rodent from the Lower Eocene Cambay Formation at Vastan, Western India, and Its Palaeobiogeographic Implications

A new ailuravine rodent, Meldimys musak sp. nov. (Mammalia: Rodentia, Ischyromyidae), is recorded from the lower Eocene lignites of western India. It is the oldest record of Rodentia from India. M. musak is more derived than the earliest Eocene ailuravine Euromys cardosoi from Portugal and more generalized than late early Eocene E. inexpectatus and Ailuravus michauxi from France. Its dental morphology closely corresponds to the middle early Eocene species M. louisi, which lived about 52 Ma in Western Europe. Meldimys was previously known only from Europe, and ailuravines were previously reported only from Europe and North America. Its occurrence in India allows the first direct correlation between the early Eocene land mammal horizons of Europe and India, and raises the possibility of a terrestrial faunal exchange between India and Eurasia close to the Palaeocene—Eocene transition.

The morphology of intrusion-related vent structures and their implications for constraining the timing of intrusive events along the NE Atlantic margin

Intrusion-related vent structures found within Palaeocene sediments and near the Palaeocene–Eocene transition in basins along the NE Atlantic margin have been studied in detail using 3D seismic data. The vents formed at the palaeo-seabed as a result of sill intrusion and the vent fill ranges in composition from entirely remobilized sedimentary to dominantly magmatic. The vents are commonly developed above sill edges and crests in sills to which they are linked by pipe- and diatreme-like structures. The vents also develop above the upper tips of deep-seated faults and at fault intersections. The vents can be used to constrain the approximate timing of igneous sill intrusion and duration of hydrothermal activity. It is estimated that using the seismically constrained stratigraphic context of these vents to establish the timing of sill emplacement is associated with an uncertainty of >100 ka and up to as much as 800 ka. Interpretation of the vents indicates that sill intrusion took place during a number of discrete phases within the Palaeocene and earliest Eocene. These structures and their timing of formation have important implications for climate change studies, basin-scale processes including fluid flow and diagenesis, as well as hydrocarbon exploration.

Early Eocene climatic, volcanic, and biotic events in the northwestern Tethyan Untersberg section, Austria

The 40 m thick Untersberg section (Salzburg, Austria) of the Northern Calcareous Alps comprises the Palaeocene–Eocene transition and spans the upper part of calcareous nannoplankton zone NP9 and the lower part of zone NP10 (sub-zone NP10a). These zones are equivalent to planktonic foraminifera zone P5 and the lower part of zone P6 (sub-zone P6a). The succession was deposited in a lower bathyal slope environment at a palaeodepth of about 2000 m. Within the dominantly marlstone succession, a 5.5-m-thick intercalation of red and green claystone and marly claystone represents the global negative carbon isotope excursion (CIE) which is used to recognize the Palaeocene–Eocene boundary. The CIE was associated with a shallowing of the calcite compensation depth by at least 1 km. Throughout the section, clay mineral assemblages are dominated by smectite, indicating a seasonal climate with alternating wet and dry conditions. A 49% increase in detrital quartz and feldspar within the CIE-interval suggests enhanced continental run-off. This was probably the result of the establishment of a monsoonal setting, in which vegetation was sparse, while periodic high rainfall caused pronounced sediment transport. The increased terrestrially derived input is associated with abundant radiolarian casts indicating high primary productivity. This suggests that seasonal nutrient pulses resulting from intensified precipitation during the wet season have caused high surface-water fertility. The benthic foraminifera faunas of the samples rich in siliceous plankton are strongly dominated by Glomospira spp., Nuttalides truempyii, Abyssamina poagi, Anomalinoides praeacutus, Anomalinoides nobilis, and Oridorsalis spp. We assume that the Glomospira–Nuttalides fauna consists of opportunistic species which quickly react to seasonally varying amounts of food. The calcareous nannoplankton assemblage of the CIE-interval is characterized by the first occurrences of the genus Rhomboaster and of Discoaster araneus and Discoaster mahmoudii, whereas Scapholithus apertus become extinct at the Palaeocene–Eocene boundary . Within nannoplankton sub-zone NP10a, a series of primarily basaltic ashes give evidence for a major episode of explosive volcanism which can be correlated with the positive ash-series of the Fur-Formation in northern Denmark. The wide dispersal distance of the tephras implies Plinian-scale eruptions and multiple ejections of large volumes of pyroclastic material.

Fruits and seeds from the Tienen Formation at Dormaal, Palaeocene–Eocene transition in eastern Belgium

The Belgian locality of Dormaal is famous for the diversity of its vertebrate faunas that illustrate part of the biota at the Palaeocene–Eocene transition in northwest Europe, 55 million years ago. This paper completes the palaeoenvironmental information with the description of fruits and seeds collected at Dormaal in the same layers as the vertebrates. Fleshy fruits, drupes and berries produced by climbing plants, especially woody lianas, (Menispermaceae, Vitaceae and Icacinaceae), are well represented. The assemblage includes also aquatic plants (Lythraceae) and trees or shrubs (Nyssaceae, ?Theaceae and ?Ericaceae). Reconstruction of the local environment confirms the analysis made from the vertebrates, and indicates the presence of a channel in a densely wooded area with a warm–humid to subtropical climate.

Astronomically-tuned chronology for the Palaeocene—Eocene transition

Astronomically-tuned chronology for the Palaeocene—Eocene transition

Distinguishing climatic and tectonic forcing of turbidite sedimentation, and the bearing on turbidite bed scaling: Palaeocene-Eocene of northern Spain

Mineral composition and carbon isotope signals of pelagic limestones and hemipelagic marlstones reveal the driving processes of interbedded turbidites. The Palaeocene to lower Eocene lower bathyal Zumaia series in northern Spain between Zumaia and Getaria (W of San Sebastian) offers this opportunity. This deep-marine series records the transition from a carbonate system (Palaeocene) to a siliciclastic system (early Eocene), mainly controlled by the initiation of Pyrenean uplift in the latest Palaeocene. During the tectonically quiet Palaeocene, varying carbonate turbidite deposition was controlled by climate-dependent production of (foramol association) carbonate debris on the carbonate shelves bordering the basin. The late Palaeocene period was characterized by a cycle of increasing and then decreasing turbidite sedimentation. Increased carbonate production was driven by comparably cool/dry climates in the late Palaeocene Atlantic region, and global marked temperature gradients which enhanced wind-driven Ekman-upwelling of nutrients. In contrast, during warm/perennially humid periods (early Palaeocene and the Palaeocene-Eocene transition) the dynamics of the carbonate turbidite deposition was sluggish, due to decreased carbonate production. In the carbonate system, frequency-size statistics of bed thicknesses show that turbidite generation occurred non-scale invariant. From the earliest Eocene, increasing siliciclastic input from the rising and west advancing Pyrenean chain is observed. After a transitional period, the highly dynamic lower Eocene siliciclastic system evolved on a prograding deep-sea fan under a perennially humid and seasonally wet climate. Several periods of increased tectonic activity and sediment input are recognized by clay mineral assemblages in interturbidite beds. Turbidite bed frequency-size statistics show a power-law distribution, implying that during such periods (particularly NP 12), the depositional system temporarily reached a self-organized critical state. The evolution of the system to critical state appears to be mainly driven by siliciclastic sediment input.

Fossil plants record an atmospheric 12 CO 2 and temperature spike across the Palaeocene-Eocene transition in NW Europe

The large negative excursion of carbon-isotope composition (δ 13 C) recorded from foraminifera and bulk carbonates indicates a major anomaly in the operation of the global carbon cycle across the Palaeocene-Eocene boundary. Therefore, we sought terrestrial evidence for the transfer of isotopically light carbon ( 12 CO 2 ) from the ocean to the atmosphere by making systematic δ 13 C measurements or well-dated sequences of fossil pollen from NW Europe. The results indicate an atmospheric 12 CO 2 spike of c. 2 % between 58 and 55 Ma coincident with the ocean isotopic anomalies. Pollen spectra from these sequences suggest a marked shift in dominance from mixed mesophytic to paratropical forests synchronous with the terrestrial isotope excursion.

Palaeogene volcanism: the sedimentary record in Denmark

Summary Approximately 200 volcanic ash layers are known from Palaeocene and Eocene marine clays in Denmark. The oldest layers are present in the upper part of the Upper Palaeocene and are sporadic, thin and acidic in composition. The main volcanic phase took place at the Palaeocene-Eocene transition. During the main phase, a supply from the N to NE is indicated, while a few layers probably had a source to the NW or W. A later volcanic phase is represented by thin and more sporadic ashes in the Lower to Middle Eocene. These are almost totally transformed to smectite. In the Upper Palaeocene, and partly in the Lower Eocene, smectite is a highly dominant clay mineral in the interbedded clays. Zeolites of the heulandite-clinoptilolite type are also present, while cristobalite is sporadically present in the lower part. A major supply of smectite from the N Atlantic may be indicated. Below the ash-bearing sequence the only evidence for volcanic activity is the presence of very smectite-rich, zeolitic clays with scattered opal-CT and slightly silicified horizons. Calculated chemical compositions of smectites from both ash layers and clay layers between ash layers and below the ash-bearing sequence are almost identical, indicating a volcanic source for the smectite.