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| Titel |
The benthic fauna from the lower Maastrichtian chalk of Kronsmoor (Saturn quarry, northern Germany): composition and palaeoecologic implications |
| VerfasserIn |
Julia Engelke, Christian Linnert, Jörg Mutterlose, Markus Wilmsen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146014
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| Publikation (Nr.) |
 EGU/EGU2017-10002.pdf |
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| Zusammenfassung |
| The Saturn quarry near Kronsmoor (northern Germany) offers an undisturbed section of
upper Campanian to lower Maastrichtian chalks. The target interval of the DFG project
“Biodiversity and plankton-benthos coupling: an integrated ecosystem analysis
from the Late Cretaceous Chalk” is focused on the lower Maastrichtian Belemnella
obtusa Zone to mid-Belemnella sumensis Zone, i.e. to the uppermost Kronsmoor
and lowermost Hemmoor formations. In this interval, a conspicuous increase in
macrofossil abundance without apparent lithofacies changes has been observed and
the project intends to integrate planktic, benthic and geochemical proxies for a
comprehensive understanding of the Chalk Sea ecosystem. The aim of this study is the
analysis of the benthic community. In a first step, the benthic body fossils of the c.
25-m-thick section were semi-quantitatively studied based on a collection of more than
1,000 specimens. Two successive benthic macrofossil assemblages were recognised:
the lower interval (upper part of the Kronsmoor Formation, B. obtusa Zone) is
characterized by low abundances, only about 100 macroinvertebrates were collected, mostly
irregular and regular echinoids, brachiopods and crinoids. The upper interval (B.
sumensis Zone) shows an eight times higher macroinvertebrate abundance and a
conspicuous dominance of brachiopods, increasing from only 30 to over 500 specimens.
In order to quantify the observed qualitative palaeoecological changes, 33 bulk
samples of about 6 kg each were retrieved in a distance of c. 0.75 m. The bulk
samples were frozen and thawed, washed and sieved in different sizes. The fraction
500 μm–1 mm and >1 mm were picked, sorted and counted. A diverse assemblage of
bryozoans, foraminifers, shell fragments of brachiopods and bivalves, spines and test
fragments of different echinoid taxa, parts of asteroids and ophiuroids, sponge debris,
crinoids and small serpulids, is present. Reduced abundances in the lower part and
generally higher abundances in the upper part are recognised. The palaeoecological
analysis of both datasets indicates different guilds, of which epifaunal suspension
feeders (fixo-sessile and libero-sessile guilds), comprising c. 50 % of the fauna in the
lower interval, increase to a dominance of c. 80 % in the upper interval, including a
considerable proportion of rhynchonelliform brachiopods. The palaeoecological data of
benthic communities at Kronsmoor are indicative of increased nutrient availability
during the early Maastrichtian. However, in the absence of any evidence of increased
productivity in the overlying photic zone (calcareous nannofossil data), a lateral input
(upwelling) of nutrient-rich waters onto the shelf to fuel the benthic ecosystem has to be
considered. This view is supported by records of contemporaneous changes in latest
Cretaceous ocean circulation that followed the latest Campanian cooling event,
inclusive of a southward spread of waters of intermediate depth from high-latitudes. |
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