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Early Eocene climatic, volcanic, and biotic events in the northwestern Tethyan Untersberg section, Austria

Egger, H; Homayoun, M; Huber, H; Rogl, F and Schmitz, Birger LU (2005) In Palaeogeography, Palaeoclimatology, Palaeoecology 217(3-4). p.243-264
Abstract
The 40 in thick Untersberg section (Salzburg, Austria) of the Northern Calcareous Alps comprises the Palaeocene-Eocene transition and spans the upper part of calcareous nannoplankton zone NP9 and the lower part of zone NP10 (subzone NP10a). These zones are equivalent to planktonic foraminifera zone P5 and the lower part of zone P6 (sub-zone P6a). The succession was deposited in a lower bathyal slope environment at a palaeodepth of about 2000 in. Within the dominantly marlstone succession, a 5.5-m-thick intercalation of red and green claystone and marly claystone represents the global negative carbon isotope excursion (CIE) which is used to recognize the Palaeocene-Eocene boundary. The CIE was associated with a shallowing of the calcite... (More)
The 40 in thick Untersberg section (Salzburg, Austria) of the Northern Calcareous Alps comprises the Palaeocene-Eocene transition and spans the upper part of calcareous nannoplankton zone NP9 and the lower part of zone NP10 (subzone NP10a). These zones are equivalent to planktonic foraminifera zone P5 and the lower part of zone P6 (sub-zone P6a). The succession was deposited in a lower bathyal slope environment at a palaeodepth of about 2000 in. Within the dominantly marlstone succession, a 5.5-m-thick intercalation of red and green claystone and marly claystone represents the global negative carbon isotope excursion (CIE) which is used to recognize the Palaeocene-Eocene boundary. The CIE was associated with a shallowing of the calcite compensation depth by at least 1 km. Throughout the section, clay mineral assemblages are dominated by smectite, indicating a seasonal climate with alternating wet and dry conditions. A 49% increase in detrital quartz and feldspar within the CIE-interval suggests enhanced continental run-off This was probably the result of the establishment of a monsoonal setting, in which vegetation was sparse, while periodic high rainfall caused pronounced sediment transport. The increased terrestrially derived input is associated with abundant radiolarian casts indicating high primary productivity. This suggests that seasonal nutrient pulses resulting from intensified precipitation during the wet season have caused high surface-water fertility. The benthic foraminifera faunas of the samples rich in siliceous plankton are strongly dominated by Glomospira spp., Nuttalides truempyii, Abyssamina poagi, Anomalinoides praeacutus, Anomalinoides nobilis, and Oridorsalis spp. We assume that the Glomospira-Nuttalides fauna consists of opportunistic species which quickly react to seasonally varying amounts of food. The calcareous nannoplankton assemblage of the CIE-interval is characterized by the first occurrences of the genus Rhomboaster and of Discoaster araneus and Discoaster mahmoudii, whereas Scapholithus apertus become extinct at the Palaeocene-Eocene boundary. Within nannoplankton sub-zone NP10a, a series of primarily basaltic ashes give evidence for a major episode of explosive volcanism which can be correlated with the positive ash-series of the Fur-Formation in northern Denmark. The wide dispersal distance of the tephras implies Plinian-scale eruptions and multiple ejections of large volumes of pyroclastic material. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
isotopes, carbon, foraminifera calcareous nannoplankton, palaeogene, volcanism, clay minerals
in
Palaeogeography, Palaeoclimatology, Palaeoecology
volume
217
issue
3-4
pages
243 - 264
publisher
Elsevier
external identifiers
  • wos:000227309900005
  • scopus:13444273126
ISSN
1872-616X
DOI
10.1016/j.palaeo.2004.12.006
language
English
LU publication?
yes
id
0c00d322-d317-42fc-92b8-1a99e7cd0701 (old id 251646)
date added to LUP
2007-08-10 11:49:04
date last changed
2017-10-29 03:24:09
@article{0c00d322-d317-42fc-92b8-1a99e7cd0701,
  abstract     = {The 40 in thick Untersberg section (Salzburg, Austria) of the Northern Calcareous Alps comprises the Palaeocene-Eocene transition and spans the upper part of calcareous nannoplankton zone NP9 and the lower part of zone NP10 (subzone NP10a). These zones are equivalent to planktonic foraminifera zone P5 and the lower part of zone P6 (sub-zone P6a). The succession was deposited in a lower bathyal slope environment at a palaeodepth of about 2000 in. Within the dominantly marlstone succession, a 5.5-m-thick intercalation of red and green claystone and marly claystone represents the global negative carbon isotope excursion (CIE) which is used to recognize the Palaeocene-Eocene boundary. The CIE was associated with a shallowing of the calcite compensation depth by at least 1 km. Throughout the section, clay mineral assemblages are dominated by smectite, indicating a seasonal climate with alternating wet and dry conditions. A 49% increase in detrital quartz and feldspar within the CIE-interval suggests enhanced continental run-off This was probably the result of the establishment of a monsoonal setting, in which vegetation was sparse, while periodic high rainfall caused pronounced sediment transport. The increased terrestrially derived input is associated with abundant radiolarian casts indicating high primary productivity. This suggests that seasonal nutrient pulses resulting from intensified precipitation during the wet season have caused high surface-water fertility. The benthic foraminifera faunas of the samples rich in siliceous plankton are strongly dominated by Glomospira spp., Nuttalides truempyii, Abyssamina poagi, Anomalinoides praeacutus, Anomalinoides nobilis, and Oridorsalis spp. We assume that the Glomospira-Nuttalides fauna consists of opportunistic species which quickly react to seasonally varying amounts of food. The calcareous nannoplankton assemblage of the CIE-interval is characterized by the first occurrences of the genus Rhomboaster and of Discoaster araneus and Discoaster mahmoudii, whereas Scapholithus apertus become extinct at the Palaeocene-Eocene boundary. Within nannoplankton sub-zone NP10a, a series of primarily basaltic ashes give evidence for a major episode of explosive volcanism which can be correlated with the positive ash-series of the Fur-Formation in northern Denmark. The wide dispersal distance of the tephras implies Plinian-scale eruptions and multiple ejections of large volumes of pyroclastic material.},
  author       = {Egger, H and Homayoun, M and Huber, H and Rogl, F and Schmitz, Birger},
  issn         = {1872-616X},
  keyword      = {isotopes,carbon,foraminifera calcareous nannoplankton,palaeogene,volcanism,clay minerals},
  language     = {eng},
  number       = {3-4},
  pages        = {243--264},
  publisher    = {Elsevier},
  series       = {Palaeogeography, Palaeoclimatology, Palaeoecology},
  title        = {Early Eocene climatic, volcanic, and biotic events in the northwestern Tethyan Untersberg section, Austria},
  url          = {http://dx.doi.org/10.1016/j.palaeo.2004.12.006},
  volume       = {217},
  year         = {2005},
}