Abstract. The early Paleogene is marked by multiple negative carbon isotope excursions
(CIEs) that reflect massive short-term carbon cycle perturbations that
coincide with significant warming during a high-pCO2 world, affecting
both marine and terrestrial ecosystems. Records of such hyperthermals from
the marine–terrestrial interface (e.g., estuarine swamps and mire deposits)
are therefore of great interest as their present-day counterparts are
highly vulnerable to future climate and sea level change. Here, we assess
paleoenvironmental changes of midlatitudinal late Paleocene–early Eocene
peat mire records along the paleo-North Sea coast. We provide carbon isotope
data of bulk organic matter (δ13CTOC), organic carbon
content (%TOC), and palynological data from an extensive peat mire
deposited at a midlatitudinal (ca. 41∘ N) coastal site
(Schöningen, Germany). The δ13CTOC data show a carbon
isotope excursion of −1.3 ‰ (mean decrease in δ13CTOC; −1.7 ‰ at the onset of CIE) coeval
with a conspicuous Apectodinium acme. Due to the exceptionally large stratigraphic
thickness of the CIE at Schöningen (10 m of section) we established a
detailed palynological record that indicates only minor changes in
paleovegetation leading into and during this event. Instead, paleovegetation
changes mostly follow natural successions in response to changes along the
marine–terrestrial interface. The available age constraints for the
Schöningen Formation hamper a solid assignment of the detected CIE to a
particular hyperthermal such as the Paleocene–Eocene Thermal Maximum
(PETM) or any succeeding hyperthermal event such as the Eocene Thermal
Maximum 2 (ETM2). Compared to other nearby peat mire records (Cobham, UK; Vasterival, F) it
appears that wetland deposits around the Paleogene North Sea have a
consistent CIE magnitude of ca. −1.3 ‰ in δ13CTOC. Moreover, the Schöningen record shares major
characteristics with the Cobham Lignite PETM record, including evidence for
increased fire activity prior to the CIE, minor plant species change during
the hyperthermal, a reduced CIE in δ13CTOC, and drowning
of the mire (marine ingressions) during much of the Schöningen CIE
event. This suggests that either the Schöningen CIE reflects the PETM or
that early Paleogene hyperthermals similarly affected paleoenvironmental
conditions of a major segment of the paleo-North Sea coast.