Marine and terrestrial environmental changes in NW Europe preceding carbon release at the Paleocene–Eocene transition

Sev Kender,Michael H Stephenson,James B Riding,Melanie J Leng,Robert W.O’B Knox,Victoria L Peck,Christopher P Kendrick,Michael A Ellis,Christopher H Vane,Rachel Jamieson

doi:10.1016/j.epsl.2012.08.011

Abstract

Environmental changes associated with the Paleocene–Eocene thermal maximum (PETM, ∼56Ma) have not yet been documented in detail from the North Sea Basin. Located within proximity to the North Atlantic igneous province (NAIP), the Kilda Basin, and the northern rain belt (paleolatitude 54°N) during the PETM, this is a critical region for testing proposed triggers of atmospheric carbon release that may have caused the global negative carbon isotope excursion (CIE) in marine and terrestrial environments. The CIE onset is identified from organic matter δ13C in exceptional detail within a highly expanded sedimentary sequence. Pollen and spore assemblages analysed in the same samples for the first time allow a reconstruction of possible changes to vegetation on the surrounding landmass. Multiproxy palynological, geochemical, and sedimentologic records demonstrate enhanced halocline stratification and terrigenous deposition well before (103yrs) the CIE, interpreted as due to either tectonic uplift possibly from a nearby magmatic intrusion, or increased precipitation and fluvial runoff possibly from an enhanced hydrologic cycle. Stratification and terrigenous deposition increased further at the onset and within the earliest CIE which, coupled with evidence for sea level rise, may be interpreted as resulting from an increase in precipitation over NW Europe consistent with an enhanced hydrologic cycle in response to global warming during the PETM. Palynological evidence indicates a flora dominated by pollen from coastal swamp conifers before the CIE was abruptly replaced with a more diverse assemblage of generalist species including pollen similar to modern alder, fern, and fungal spores. This may have resulted from flooding of coastal areas due to relative sea level rise, and/or ecologic changes forced by climate. A shift towards more diverse angiosperm and pteridophyte vegetation within the early CIE, including pollen similar to modern hickory, documents a long term change to regional vegetation.

Highlights

The PETM was a period of geologically-rapid global warming that punctuated a warming Eocene climate 55.8 Ma ago (Charles et al, 2011), and saw sea surface temperatures rise by 5–8 1C from background levels (Zachos et al, 2005; Sluijs et al, 2007)
In this study we focus on paleoenvironmental signals from a high resolution marine core collected from the central North Sea (Fig. 1), in order to understand changes to precipitation, ocean stratification, productivity and vegetation over the onset of the PETM
Our results provide the first evidence that the North Sea became stratified from 103 yrs before the carbon isotope excursion (CIE) onset

Summary

Introduction

The PETM was a period of geologically-rapid global warming that punctuated a warming Eocene climate 55.8 Ma ago (Charles et al, 2011), and saw sea surface temperatures rise by 5–8 1C from background levels (Zachos et al, 2005; Sluijs et al, 2007) It was associated with a substantial injection of d13C-depleted carbon into the ocean-atmosphere system (see Pagani et al, 2006a) over o20 ka (Cui et al, 2011), causing a negative carbon isotope excursion (CIE) between À 2 and À 7% in marine and terrestrial sediments (see overview in Schouten et al, 2007). Kender et al / Earth and Planetary Science Letters 353–354 (2012) 108–120

Methods

Results

Conclusion