Early Eocene Climatic Optimum

The Eocene Green River Formation and associated fluvial strata host a large variety of widely distributed and laterally extensive synsedimentary to early post-depositional deformation features. Although mostly overlooked in past studies, these structures provide insight into the rheology of the sediments and hydrodynamic conditions at the time of deformation. They also have implications about basin configuration and bottom topography, as well as the structural history of the region.
In the Uinta and Piceance Creek Basins of Utah and Colorado, deformed intervals are present in littoral (sand-dominated) to profundal (oil shale) lacustrine deposits, as well as fluvial facies. Deformation structures exhibit a wide range of morphology, size, and style, ranging from ductile (convolution, folding, load and pinch-and-swell structures) to brittle (microfaults, breccias), to sedimentary injection into fissures and cracks forming dikes, to various mass transport deposits. In most cases, these layers are bound above and below by undisturbed beds of similar facies with horizontal bedding planes, which implies short-lived but recurring events that affected only sediments with a susceptible rheological state. Deformation typically occurred intrastratally, i.e. under shallow burial. The variations in deformation style, size, morphology, and areal extent are related to differences in grain size and type, water content, cementation, organic content, thickness of susceptible material, lateral facies variation, and the nature of the driving force. Some of the sedimentary injection features overprint each other, indicating multiple events affecting a single interval.
We interpret most of these features as seismically induced (‘seismites’) based on: (1) the tectonic setting of the basin; (2) the sedimentary environment and sedimentological characteristics of the host succession; (3) the lateral extent of deformation structures; (4) their recurrence at different stratigraphic levels; and (5) their similarity to those ascribed to seismically induced deformation elsewhere and reproduced experimentally. They developed as a result of increased pore pressure and a complex combination of extensional, compressive, and shear stresses acting in many directions caused by shaking during strong earthquakes. Mass transport deposits indicate in situ disruption and failure of the imperceptibly dipping lake floor. These ‘seismites’ represent the direct sedimentary record of syndepositional tectonic activity in the Uinta Basin.

This study describes 21 species of Caenogastropoda collected in the Macunköy section from the upper part of the Kırkkavak Formation (Haymana-Polatlı Ba- sin, SW of Ankara). The known stratigraphical range of the studied species is consistent with an earlyYpresian (early Eocene) age of the deposits, indicated by Cerithium puigcercosensis (Cossmann, 1897) n. comb. and Tympanotonos turris (Deshayes, 1833). This result supports previous biostratigraphic studies based on benthic foraminifers. Among the caenogastropods from the Macunköy section, two new species are described: Bellatara ankaraensis n. sp. and Vicinoceri thium seni n. sp. Furthermore, Cerithium puigcercosensis n. comb. is described as a new combination. The gastropod assemblage of the M acunköy section indicates a mangrove-fringed, wet coastal ecosystem with euryhaline conditions, connected to coastal swamps and a delta system.

Estimates of pCO2 for the early Paleogene vary widely, from near modern-day levels to an order of magnitude greater, based on various proxy measures. Resolving the relationship between climate and pCO2 during this globally warm period is a key task in understanding climate dynamics in a warmer world. Here, we use the stomatal frequency of fossil Ginkgo adiantoides from the Okanagan Highlands of British Columbia, Canada to estimate pCO2 during the Early Eocene Climatic Optimum (EECO), the interval of peak warmth in the Cenozoic. We also examine a dataset of modern Ginkgo biloba leaves to critically assess the accuracy and precision of stomatal frequency as a proxy indicator of pCO2. Early Eocene fossil G. adiantoides has significantly lower stomatal frequency than modern G. biloba, suggesting pCO2 levels N2× modern preindustrial values. This result is in contrast to earlier studies using stomatal frequency of Ginkgo that indicated near modern-day levels of pCO2 in the early Paleogene, though not including samples from the EECO. We also find that levels of pCO2 as indicated by stomatal frequency are correlated with trends in climate (mean annual temperature) over time at the Falkland fossil locality, suggesting that climate and pCO2 were coupled during the EECO hyperthermal.

This paper presents the first detailed report on mid-Holocene faunal and artefactual observations from Deurspring 16 (DSP16) shell midden situated on the central West Coast of South Africa. DSP16 also yielded late Holocene material. Until recently, the mid-Holocene record eschewed most but not all research efforts. Likewise, systematic studies on the abundant late-Holocene record of this region suggest a trajectory of hunter-gatherer resource intensification and limited group mobility. DSP16 observations show that mid-Holocene group mobility involved long distances and that visits were either brief and/or undertaken by small groups. People procured large and small terrestrial prey, and shellfish were a dietary complement. Stone tool kits were manufactured on mostly exotic silcrete, with scrapers and backed pieces being dominant among formal tools. Subsequent late-Holocene patterns shifted radically: site visits were probably longer, mobility became increasingly circumscribed to the coast and Sandveld, and subsistence relied heavily on marine resources while small terrestrial prey was also procured. Locally-available quartz and quartzite was favoured over silcrete in stone tool production, and backed pieces were gradually dropped in favour of scrapers among formal tools. These results and those from other sites show that i) the central West Coast was not as uninhabited during the mid-Holocene as previously thought, and that ii) a late-Holocene resource intensifi-cation model adequately accounts for the settlement and subsistence trends in this region.

Wildfire activity in early Paleogene greenhouse conditions can be used as an analogue to gauge the effect of future warming trends on wildfire in the current climate system. Inertinite (fossil charcoal in coal) from 11 autochthonous early Paleogene lignite seams from the Schöningen mine (Germany) was quantified using macerations, in situ pillars and industry standard crushed samples. A new three transect method was developed to quantify in situ charcoal. The combination of in situ pillars and crushed samples accounts for temporal and spatial variation in charcoal through a stratigraphically oriented pillar, whilst maintaining comparability with industry standards and previous work. Charcoal occurs as a range of randomly distributed particle sizes, indicating that fires were burning locally in the Schöningen peat-forming environment and in the surrounding areas, but according to petrological data, not in an episodic or periodic pattern. Although charcoal abundance is low (relative to previous high fire worlds such as the Cretaceous), three quantitative and semi-quantitative methods show increased wildfire activity (relative to the modern world) in the warmest parts of the early Paleogene. As atmospheric oxygen levels stabilised to modern values and precipitation and humidity became the main control on wildfire, increased rainfall followed by drier intervals would have created an environment rich in dry fuel in which wildfires could easily propagate if humidity was low enough. In the later part of the Early Eocene (Ypresian) charcoal abundance fell to levels similar to those found in modern peats. This indicates that the transition to the modern low fire world occurred within the Early Eocene, earlier than previous records suggest.

Following extreme climatic warming events, Eocene Lagerstätten document aquatic and terrestrial vertebrate faunas surprisingly similar to modern counterparts. This transition in marine systems is best documented in the earliest teleost-dominated coral reef assemblage of Pesciara di Bolca, northern Italy, from near the end of the Eocene Climatic Optimum. Its rich fauna shows similarities with that of the modern Great Barrier Reef in niche exploitation by and morphological disparity among teleost primary consumers. However, such paleoecological understanding has not transcended trophic levels above primary consumers, particularly in carcharhiniform sharks. We report an exceptionally preserved fossil school shark (Galeorhinus cuvieri) from Pesciara di Bolca. In addition to the spectacular preservation of soft tissues, including brain, muscles, and claspers, this male juvenile shark has stomach contents clearly identifiable as a sphyraenid acanthomorph (barracuda). This association prov...