In:
Geological Journal, Wiley, Vol. 56, No. 2 ( 2021-02), p. 768-785
Abstract:
Brown coal deposits of the Lower Rhine Basin, northwest Germany, cover the late Burdigalian to Serravallian and most of the Tortonian enabling access to observations of vegetation dynamics during the Miocene Climatic Optimum and Late Miocene Cooling. Based on a total of 500 microfloras sampled from brown coal seams in the Bergheim and Inden open cast mines, structural changes in the vegetation are studied in comparatively stable environments of persisting coastal mires. In order to minimize the impact of local edaphic conditions in the peat bog, the palynomorph record is characterized as diversity using plant functional types (PFTs). In total, 41 herbaceous and arboreal PFTs are assigned to pollen and spores types based on their botanical affinity.The diversity spectra reveal a variable proportion of herbaceous and shrubby PFTs attaining a mean of 30%, in both the middle and late Miocene sample sets. With ca. 70% of the total diversity attributable to arboreal functional types, the peat‐forming vegetation of the studied Miocene strata classifies as a swamp forest. The composition of the arboreal fraction shows a long‐term declining trend in the proportions of thermophilous evergreen types among broadleaved PFTs following the overall climate cooling throughout the studied time. Conifers became more diverse during the Langhian (ca. 15%, at a mean) and attained a high diversity level of ca. 20% of the total PFT diversity in the Tortonian. The diversity proportions of conifer PFTs among other arboreal components and the composition of the broadleaved angiosperm PFT fraction display a pointed short‐term variability that could probably be related to eccentricity cycles when considering the available independent stratigraphic framework. Our results suggest a distinct coupling of the structure of the peat‐forming vegetation and continental climate variability in the study area.
Type of Medium:
Online Resource
ISSN:
0072-1050
,
1099-1034
Language:
English
Publisher:
Wiley
Publication Date:
2021
detail.hit.zdb_id:
1479201-1
SSG:
13
