Stratigraphic and sedimentological aspects of the worldwide distribution of Apectodinium in Paleocene/Eocene Thermal Maximum deposits

Abstract

The Paleocene/Eocene Thermal Maximum (PETM) is characterized by pronounced global warming and associated environmental changes. In the more-or-less two decades since prior regional syntheses of Apectodinium distribution at the PETM, extensive biological and geochemical datasets have elucidated the effect of rising world temperatures on climate and the biome. A Carbon Isotope Excursion (CIE) that marks the Paleocene/Eocene Boundary (PEB) is associated with an acme of marine dinocysts of the genus Apectodinium in many locations. Distinctive foraminiferal and calcareous nannofossil populations may also be present.For this up-dated, dinocyst-oriented view of the PETM, data from worldwide locations have been evaluated with an emphasis on stratigraphic and sedimentological context. What has emerged is that a change in lithology is common, often to a distinctive siltstone or claystone unit, which contrasts with underlying and overlying lithotypes. This change, present in shallow marine/coastal settings and in deepwater turbidite deposits, is attributed to radical modifications of precipitation and erosional processes. An abrupt boundary carries the implication that some time (of unknowable duration) is potentially missing, which then requires caution in the interpretation of the pacing of events in relation to that boundary. In most instances an ‘abrupt’ or ‘rapid’ CIE onset can be attributed to a data gap at a hiatus, particularly in shallow shelf settings where transgression resulted from sea-level rise associated with the PETM. Truly gradational lower boundaries of the PETM interval are quite unusual, and if present, are poorly known so far. Gradational upper boundaries are more common, but erosional upper boundaries have been reported.Taxonomic changes have been made to clarify identification issues that have adversely impacted some biostratigraphic interpretations. Apectodinium hyperacanthum has been retained in Wetzeliella, its original genus. The majority of specimens previously assigned to Apectodinium hyperacanthum or Wetzeliella (Apectodinium) hyperacanthum have been re-assigned to an informal species, Apectodinium sp. 1. Dracodinium astra has been retained in its original genus as Wetzeliella astra, and is emended.

Early Eocene carbon isotope excursions in a lignite-bearing succession at the southern edge of the proto-North Sea (Schöningen, Germany)

“…Similar transitions from terrestrial to brackish deposits in conjunction with the PETM at the southern edge of the North Sea Basin were also reported from other sites, such as Cobham in southeastern England (Collinson et al, 2003) and the Oise region in France (Cavagnetto, 2000;Nel et al, 1999;Dupuy et al, 2014). Therefore, our carbon isotope record is consistent with peat formation during the onset of the PETM and widespread inundation of coastal lowlands due to sea level rise during a later stage of the PETM (see, e.g., Denison, 2021).…”

“…Most likely, admixture of marine organic matter more depleted in 13 C compared to terrestrial organic matter prevented the full recovery to δ 13 C TOC values as high as those recorded in the purely terrestrial organic matter of the Main Seam. However, the shift from the negative peak of δ 13 C TOC values at the top of the Main Seam to increasing values in the interbed at or near the lithological boundary has to be treated with caution since the PETM-driven transgression in this coastal setting may have led to a hiatus at the top of the Main Seam (Denison, 2021) that obscured an even more negative shift of δ 13 C TOC values.…”

Stratigraphic expression of the Paleocene-Eocene Thermal Maximum climate event during long-lived transient uplift—An example from a shallow to deep-marine clastic system in the Norwegian Sea

“…Jolley et al (2021) demonstrated that the PETM predated subaerial exposure and the formation of the Flett unconformity in the FSB in the same way as the PETM predates the Y1 subaerial unconformity in the Froan Basin. Since the PETM is considered a regional datum (Denison, 2021), this comparison shows that there was no delayed transient uplift in the Froan Basin compared to the FSB. Within the resolution of biostratigraphic data, it appears that maximum uplift and subaerial exposure was broadly time equivalent across the region.…”

Carbon isotope chemostratigraphy, geochemistry, and biostratigraphy of the Paleocene–Eocene Thermal Maximum, deepwater Wilcox Group, Gulf of Mexico (USA)

“…The marine biotic response to the climatic warming event of the PETM is well documented in localities worldwide (e.g., Thomas and Shakleton, 1996;Kahn and Aubry, 2004;Crouch et al, 2001;Sluijs et al, 2007a;Denison, 2021) and in the GOM, where it is reflected in assemblage changes or turnover in specific groups of single-celled planktonic organisms, most notably marine dinoflagellates, benthic foraminifera, and calcareous nannoplankton. Interpreting the deepwater GOM record at any single location may be complicated by a limited recovery of calcareous microfossils, but distinct trends noted in wells across the basin and in the Anchor 3 core suggest that multiple factors played a role in calcareous and organic fossil abundances.…”