Geochemical indications for the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals in terrestrial sediments of the Canadian Arctic

During the late Paleocene to early Eocene, clastic fluvial sediments and coals were deposited in northern high latitudes as part of the Marga­ret Formation at Stenkul Fiord (Ellesmere Island, Nunavut, Canada). Syn-sedimentary tectonic movements of the Eurekan deformation continu­ously affected these terrestrial sediments. Different volcanic ash layers occur, and unconformities subdivide the deposits into four sedimentary units. Rare vertebrate fossils indicate an early Eocene (Graybullian) age for the upper part of the Stenkul Fiord outcrop. Here, we present carbon isotope data of bulk coal, related organic-rich mud and siltstones, a plant leaf wax-derived alkane, and additional plant remains. These data provide a complete carbon isotope record of one stratigraphic section with defined unconformity positions and in relation to other Eurekan deformation features. A previously dated ash layer MA-1 provided a U-Pb zircon age of 53.7 Ma and is used as a stratigraphic tie point, together with a discrete negative carbon isotope excursion found above MA-1 in a closely sampled coal seam. The excursion is identified as the likely expression of the I-1 hyperthermal event. Based on our isotope data that reflect the early Eocene dynamics of the carbon cycle, this tie point, and previous paleontological constraints from vertebrate fossils, the locations of the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals and their extent along the complete section are herein identified. Within the intervals of the PETM and ETM-2 hyperthermal events, increasing amounts of clastic sediments reached the site toward the respective end of the event. This is interpreted as a response of the fluvial depositional system to an intensified hydrological system during the hyperthermal events. Our study establishes an enhanced stratigraphic framework allowing for the calcula­tion of average sedimentation rates of different intervals and considerations on the completeness of the stratigraphic record. As one of the few high-latitude outcrops of early Eocene terrestrial sediments, the Stenkul Fiord location offers further possibilities to study the effects of extreme warming events in the Paleogene.

Paleoenvironmental Conditions during the Paleocene–Eocene Transition Imprinted within the Glauconitic Giral Member of the Barmer Basin, India

The roughly 6 m thick limestone–green shale alternation within the lignite-bearing Giral Member of the Barmer Basin corresponds to a marine flooding event immediately after the Paleocene–Eocene transition. A detailed characterization of the glauconite using Electron Probe Micro Analyzer (EPMA), X-Ray Diffraction (XRD), Mössbauer and Field Emission Gun-Scanning Electron Microscope (FEG-SEM) reveals its origin in the backdrop of prevailing warm climatic conditions. The glauconite pellets vary from fine silt-sized to coarse sand-sized pellets, often reaching ~60% of the rock by volume. Mineralogical investigation reveals a ‘nascent’ to ‘slightly evolved’ character of the marginal marine-originated glauconite showing considerable interstratification. The chemical composition of the glauconite is unusual with a high Al2O3 (>10 wt%) and moderately high Fe2O3(total) contents (>15 wt%). While the K2O content of these glauconites is low, the interlayer sites are atypically rich in Na2O, frequently occupying ~33% of the total interlayer sites. The Mössbauer spectrum indicates 10% of the total iron is in ferrous form. High tetrahedral Al3+ of these glauconites suggests a high-alumina substrate that transformed to glauconite by octahedral Al-for-Fe substitution followed by the addition of K into the interlayer structure. The unusually high Na2O suggests the possibility of a soda-rich pore water formed by the dissolution of alkaline volcanic minerals. The Giral glauconite formation could have been a part of the major contributors in the Fe-sequestration cycle in the Early Eocene shelves. Warm climate during the Early Eocene time favored the glauconitization because of the enhanced supply of Fe, Al, and Si and proliferation of an oxygen-depleted depositional environment.

Paleoenvironmental analysis of early Eocene marl and limestone alternations from Mead Stream, New Zealand

<p>This study integrates paleonotology and geochemistry to provide a paleoclimatic analysis of cyclic sedimentation in the Lower Marl at Mead Stream in Marlborough, Aotearoa/New Zealand. The alternating marl and limestone bedding in this outcrop coincide with the warmest period in the Paleogene, the Early Eocene Climatic Optimum (EECO). An acetic acid leaching method was refined and used successfully to extract microfossils from the indurated limestones and marls from two intervals of the Lower Marl. The technique resulted in foraminiferal tests with improved surface ornament in comparison with samples that were processed using standard washing methodology. The resulting paleontological assessment of leached foraminiferal and radiolarian assemblages coupled with XRF and stable isotope analysis revised the position and detailed the faunal response to the J hyperthermal at the initiation of the EECO. Microfossil assemblages and carbon isotopic data suggest that the J carbon isotopic excursion (CIE) may be a two-stage event. A new L-3 CIE and possible hyperthermal event was identified within the body of the EECO. Both the J and L-3 events contained acmes where Morozovella made up a quarter of the planktic foraminiferal specimens, suggesting the southern expansion of subtropical waters. Fluctuations of Acarinina and Subbotina foraminifera coinciding with the marl and limestone alternations may indicate climate cycles within these hyperthermals.</p>

Early Eocene Palynology from Mead Stream, New Zealand

<p>This study documents the first detailed palynological analysis of early Eocene strata from the Lower Marl unit at Mead Stream, southern Marlborough, New Zealand. Examination of marine palynomorph assemblages and palynofacies analysis were used to improve biostratigraphic resolution and investigate paleoclimate across the Early Eocene Climatic Optimum (EECO; ~53–49 Ma)—a period characterised by the highest temperatures of the Paleogene. Early Eocene New Zealand dinocyst zones from NZE2–NZE4, and the Charlesdowniea coleothrypta zone are established across the Lower Marl for the first time in this study. Marine palynomorph assemblages originating in outer-neritic conditions and deposited on the upper slope represent low energy transport along the margin of a terrestrial discharge plume. Palynomorph assemblages do not provide insight into sea surface temperature (SST) trends. Palynomorph assemblages may reflect extremely low surface productivity. Cycles in organic matter between marine-dominant limestones to terrestrial-dominant marls, controlled by changes in temperature and seasonal precipitation, may represent orbital forcing by way of precession cycles; however the limited range of high resolution data from this study cannot statistically confirm this. An overall increase of allochthonous organic matter across the Lower Marl is likely representative of long-term background warming, culminating in peak EECO temperatures. The base of a hyperthermal, represented by carbon isotope excursion (CIE) previously identified at Mead Stream has been redefined in this study. High abundances of warm water, extreme salinity taxa coincide with the onset of this warming event.</p>

Early Eocene Palynology from Mead Stream, New Zealand

<p>This study documents the first detailed palynological analysis of early Eocene strata from the Lower Marl unit at Mead Stream, southern Marlborough, New Zealand. Examination of marine palynomorph assemblages and palynofacies analysis were used to improve biostratigraphic resolution and investigate paleoclimate across the Early Eocene Climatic Optimum (EECO; ~53–49 Ma)—a period characterised by the highest temperatures of the Paleogene. Early Eocene New Zealand dinocyst zones from NZE2–NZE4, and the Charlesdowniea coleothrypta zone are established across the Lower Marl for the first time in this study. Marine palynomorph assemblages originating in outer-neritic conditions and deposited on the upper slope represent low energy transport along the margin of a terrestrial discharge plume. Palynomorph assemblages do not provide insight into sea surface temperature (SST) trends. Palynomorph assemblages may reflect extremely low surface productivity. Cycles in organic matter between marine-dominant limestones to terrestrial-dominant marls, controlled by changes in temperature and seasonal precipitation, may represent orbital forcing by way of precession cycles; however the limited range of high resolution data from this study cannot statistically confirm this. An overall increase of allochthonous organic matter across the Lower Marl is likely representative of long-term background warming, culminating in peak EECO temperatures. The base of a hyperthermal, represented by carbon isotope excursion (CIE) previously identified at Mead Stream has been redefined in this study. High abundances of warm water, extreme salinity taxa coincide with the onset of this warming event.</p>

Paleoenvironmental analysis of early Eocene marl and limestone alternations from Mead Stream, New Zealand

<p>This study integrates paleonotology and geochemistry to provide a paleoclimatic analysis of cyclic sedimentation in the Lower Marl at Mead Stream in Marlborough, Aotearoa/New Zealand. The alternating marl and limestone bedding in this outcrop coincide with the warmest period in the Paleogene, the Early Eocene Climatic Optimum (EECO). An acetic acid leaching method was refined and used successfully to extract microfossils from the indurated limestones and marls from two intervals of the Lower Marl. The technique resulted in foraminiferal tests with improved surface ornament in comparison with samples that were processed using standard washing methodology. The resulting paleontological assessment of leached foraminiferal and radiolarian assemblages coupled with XRF and stable isotope analysis revised the position and detailed the faunal response to the J hyperthermal at the initiation of the EECO. Microfossil assemblages and carbon isotopic data suggest that the J carbon isotopic excursion (CIE) may be a two-stage event. A new L-3 CIE and possible hyperthermal event was identified within the body of the EECO. Both the J and L-3 events contained acmes where Morozovella made up a quarter of the planktic foraminiferal specimens, suggesting the southern expansion of subtropical waters. Fluctuations of Acarinina and Subbotina foraminifera coinciding with the marl and limestone alternations may indicate climate cycles within these hyperthermals.</p>

Climate and ecology in the Rocky Mountain interior after the early Eocene Climatic Optimum

As atmospheric carbon dioxide (CO2) and temperatures increase with modern climate change, ancient hothouse periods become a focal point for understanding ecosystem function under similar conditions. The early Eocene exhibited high temperatures, high CO2 levels, and similar tectonic plate configuration as today, so it has been invoked as an analog to modern climate change. During the early Eocene, the greater Green River Basin (GGRB) of southwestern Wyoming was covered by an ancient hypersaline lake (Lake Gosiute; Green River Formation) and associated fluvial and floodplain systems (Wasatch and Bridger formations). The volcaniclastic Bridger Formation was deposited by an inland delta that drained from the northwest into freshwater Lake Gosiute and is known for its vast paleontological assemblages. Using this well-preserved basin deposited during a period of tectonic and paleoclimatic interest, we employ multiple proxies to study trends in provenance, parent material, weathering, and climate throughout 1 million years. The Blue Rim escarpment exposes approximately 100 m of the lower Bridger Formation, which includes plant and mammal fossils, solitary paleosol profiles, and organic remains suitable for geochemical analyses, as well as ash beds and volcaniclastic sandstone beds suitable for radioisotopic dating. New 40Ar / 39Ar ages from the middle and top of the Blue Rim escarpment constrain the age of its strata to ∼ 49.5–48.5 Myr ago during the “falling limb” of the early Eocene Climatic Optimum. We used several geochemical tools to study provenance and parent material in both the paleosols and the associated sediments and found no change in sediment input source despite significant variation in sedimentary facies and organic carbon burial. We also reconstructed environmental conditions, including temperature, precipitation (both from paleosols), and the isotopic composition of atmospheric CO2 from plants found in the floral assemblages. Results from paleosol-based reconstructions were compared to semi-co-temporal reconstructions made using leaf physiognomic techniques and marine proxies. The paleosol-based reconstructions (near the base of the section) of precipitation (608–1167 mm yr−1) and temperature (10.4 to 12.0 ∘C) were within error of, although lower than, those based on floral assemblages, which were stratigraphically higher in the section and represented a highly preserved event later in time. Geochemistry and detrital feldspar geochronology indicate a consistent provenance for Blue Rim sediments, sourcing predominantly from the Idaho paleoriver, which drained the active Challis volcanic field. Thus, because there was neither significant climatic change nor significant provenance change, variation in sedimentary facies and organic carbon burial likely reflected localized geomorphic controls and the relative height of the water table. The ecosystem can be characterized as a wet, subtropical-like forest (i.e., paratropical) throughout the interval based upon the floral humidity province and Holdridge life zone schemes. Given the mid-paleolatitude position of the Blue Rim escarpment, those results are consistent with marine proxies that indicate that globally warm climatic conditions continued beyond the peak warm conditions of the early Eocene Climatic Optimum. The reconstructed atmospheric δ13C value (−5.3 ‰ to −5.8 ‰) closely matches the independently reconstructed value from marine microfossils (−5.4 ‰), which provides confidence in this reconstruction. Likewise, the isotopic composition reconstructed matches the mantle most closely (−5.4 ‰), agreeing with other postulations that warming was maintained by volcanic outgassing rather than a much more isotopically depleted source, such as methane hydrates.

First record of a homolid crab (Crustacea: Decapoda: Homoloidea) from the early Eocene of the Iberian Peninsula

We describe a new species of homolid crab from the Ypresian (early Eocene) Roda Formation of Huesca province (Aragon, Spain). In spite of the fragmentary condition of the sole specimen, some preserved frontal elements, and in particular the complete left cheliped, allow inclusion it within the genus Paromola Wood-Mason in Wood-Mason and Alcock, 1891, based on morphological similarities with the extant species of this genus. Direct comparison with specimens of the extant Paromola cuvieri (Risso, 1815) confirms this systematic assignment. Paromola bretoni n. sp. is the first homolid reported in the Cenozoic of the Iberian Peninsula, and expands the rich decapod fossil record of the Eocene basins of southern Pyrenees.

New data on the age of the Emine Formation (East Balkan, Bulgaria)

The study represents new data about chronostratigraphic range of the Emine flysch Formation in its type section at the Black Sea coast near the “Irakli” touristic resort. In the highest stratigraphic levels, calcareous nannofossils of NP 10 Rhomboaster bramlettei zone have been documented, supporting early Eocene age for the formation. These new finds will shed light on the timing of cessation of the turbiditic sedimentation in East Balkan, as well as on the specific expression of the global event – the Paleocene–Eocene Thermal Maximum (PETM) in deep-water environment.