Greenhouse conditions in lower Eocene coastal wetlands?-Lessons from Schöningen, Northern Germany.

Olaf K Lenz,Volker Wilde,Walter Riegel,Borja Cascales-Miñana

doi:10.1371/journal.pone.0232861

Olaf K Lenz, Volker Wilde + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0232861

Copy DOI

Abstract

The Paleogene succession of the Helmstedt Lignite Mining District in Northern Germany includes coastal peat mire records from the latest Paleocene to the middle Eocene at the southern edge of the Proto-North Sea. Therefore, it covers the different long- and short-term climate perturbations of the Paleogene greenhouse. 56 samples from three individual sections of a lower Eocene seam in the record capture the typical succession of the vegetation in a coastal wetland during a period that was not affected by climate perturbation. This allows facies-dependent vegetational changes to be distinguished from those that were climate induced. Cluster analyses and NMDS of well-preserved palynomorph assemblages reveal four successional stages in the vegetation during peat accumulation: (1) a coastal vegetation, (2) an initial mire, (3) a transitional mire, and (4) a terminal mire. Biodiversity measures show that plant diversity decreased significantly in the successive stages. The highly diverse vegetation at the coast and in the adjacent initial mire was replaced by low diversity communities adapted to wet acidic environments and nutrient deficiency. The palynomorph assemblages are dominated by elements such as Alnus (Betulaceae) or Sphagnum (Sphagnaceae). Typical tropical elements which are characteristic for the middle Eocene part of the succession are missing. This indicates that a more warm-temperate climate prevailed in northwestern Germany during the early lower Eocene.

Highlights

The long-term warming trend of the early Paleogene greenhouse climate culminated in the Early Eocene Climatic Optimum (EECO) between c. 52 and 50 Ma before present (BP) [1]
It was interrupted by short-term warming events, the most prominent being the PaleoceneEocene Thermal Maximum (PETM or ETM-1, e.g., [2,3,4]), which is associated with rapid temperature increases at the transition between the Paleocene and Eocene, which is estimated to have lasted about 170 (± 30) kyr [5,6,7]
Statistical scrutiny by means of Cluster analyses and Non-metric multidimensional scaling (NMDS) shows that 5 different pollen zones (PZs) occurring in vertical succession can be clearly distinguished in the three sections of Seam 1 despite local differences between them

Summary

Introduction

The long-term warming trend of the early Paleogene greenhouse climate culminated in the Early Eocene Climatic Optimum (EECO) between c. 52 and 50 Ma before present (BP) [1]. 52 and 50 Ma before present (BP) [1] It was interrupted by short-term warming events, the most prominent being the PaleoceneEocene Thermal Maximum (PETM or ETM-1, e.g., [2,3,4]), which is associated with rapid temperature increases at the transition between the Paleocene and Eocene, which is estimated to have lasted about 170 (± 30) kyr [5,6,7]. Lower Eocene coastal wetlands of Northern Germany Recognition of these thermal events has originally been based on carbon isotope excursions (CIE) observed in deep sea cores (e.g., [2, 8, 10, 12,13,14,15]) and considered to result from massive release of light carbon (C13) to the atmosphere (e.g., [16, 17]). In order to develop a more coherent picture of the effects of climate in general and thermal events on the early Eocene vegetation, additional case studies are needed

Methods

Results

Discussion

Conclusion