期刊
SEDIMENTARY GEOLOGY
卷 241, 期 1-4, 页码 40-51出版社
ELSEVIER
DOI: 10.1016/j.sedgeo.2011.09.010
关键词
Ichnofossils; Salinity; Oxygenation; Mud; Holocene; Baltic Sea
类别
资金
- European Community [217246]
- Academy of Finland
- Bundesministerium fur Bildung und Forschung (BMBF) [03F0496A]
- Russian Foundation for Basic Research (RFBR) [08-05-92420]
- BONUS
Late Holocene sediments in the Baltic Sea provide an opportunity to study lateral changes in the assemblages of identifiable biogenic sedimentary structures (ichnofossils) in a large, high-latitude semi-enclosed sea with instrumentally determined gradients in biodiversity and environmental factors such as salinity and oxygen availability. Integrated sedimentological and ichnological analysis is carried out on 6 long cores collected along an open-sea, declining salinity transect across the basin. Muddy sediments in euhaline (Kattegat) and polyhaline (Mecklenburg Bight) sites are characterized by the archetypal Cruziana Ichnofacies, portrayed by subsurface deposit-feeding structures (Scolicia and Planolites), surface deposit-feeding structures (Skolithos), and structures that reflect both these feeding strategies (Palaeophycus, Arenicolites/Polykladichnus and unnamed biodeformational structures produced by bivalves). The ichnofossils are tiered to 3 levels. The Cruziana Ichnofacies is impoverished in the higher mesohaline Arkona Basin and even more so with declining salinity farther inland. The deepest, oxygen-restricted study sites (Gotland Deep and the western Gulf of Finland) below a permanent halocline are characterized by very small and shallow deposit-feeding structures (Planolites and rare flat Arenicolites/Polykladichnus), and poorly developed tiering. The nearly freshwater eastern Gulf of Finland is characterized by the Cenozoic archetypal Mermia Ichnofacies, dominated by narrow and shallow subsurface and surface deposit-feeding structures (Planolites and flat Arenicolites/Polykladichnus). Large Planolites (3-7 mm in diameter) at this site are untypical of Mermia Ichnofacies assemblages. These results confirm the earlier observations that marine forms dominate brackish-water ichnoassemblages, with the ichnofossil size and diversity decreasing with declining salinity. The results also confirm the predicted decreases in the ichnofossil size and vertical extent at low-oxygen levels. Poorly developed tiering is a particularly useful indicator of oxygen stress in the salinity-restricted system. (C) 2011 Elsevier B.V. All rights reserved.
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