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| Titel |
Large volcanic eruptions and the PETM: Geochemistry from the Fur Formation, Denmark |
| VerfasserIn |
Morgan Jones, Henrik Svensen, Christian Tegner, Sverre Planke, Pi Willumsen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110833
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| Publikation (Nr.) |
 EGU/EGU2015-10873.pdf |
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| Zusammenfassung |
| The opening of the North Atlantic Ocean during the early Cenozoic was accompanied by
substantial volcanism that resulted in the deposition of numerous ash layers over much of
northern Europe. This volcanism was contemporaneous with the extreme greenhouse climate
of the Palaeocene-Eocene Thermal Maximum (PETM), and is therefore of particular
interest for volcanism-climate interactions. The island of Fur, northern Denmark,
contains abundant outcrops of volcanic ash layers deposited in a shallow marine
environment. Over 179 distinct ash horizons (those greater than ~1 cm are numbered #-39
to #+140) are found within the ~60 m thick Fur Formation. The ash layers are
predominantly black and composed of volcanic glass particles ranging from silt to
sand in size. Each bed is normally graded and lacks any evidence of significant
reworking. There were no volcanoes in the vicinity of Fur during this time, and the
outcrops are >700 km from the break-up axis, indicating that at least some of the ash
layers were formed during very large eruptions and transported a long way from the
source volcanoes. A few thick grey ash layers (e.g. #-33 and #+19) are believed to
have originated from volcanoes in East Greenland. Here we present geochemical
data from two key sections within the Fur Formation, a beach section at Stolleklint
where ashes #-34 to #-31 are exposed, and a quarry section at Jenshøj that covers
ashes #+17 to #+35. The #-33 and #+19 ashes are both prominent marker horizons
around 15-20 cm thick. The Stolleklint section is clay rich while the quarry section is
dominated by diatomite. At Stolleklint, bulk rock total organic carbon (TOC) δ13C
values throughout a 1.5 m section are relatively steady at -30.7 to -31.7 o typical
of the carbon isotope excursion values of the PETM at Fur. Just above ash layer
#-33, δ13C = -27.9 o characteristic of post-PETM values. The bulk rock TOC is
high, 1.5 to 4 wt. %. The post-PETM quarry section is much poorer in organic
material (0-0.5 wt. % TOC). Values of δ13C are more varied than at Stolleklint, scatter
around -28.0 ‰ in the lower 0.5 m. A small negative δ13C excursion occurs just
above the thick #+19 ash layer, followed by a slow recovery to less negative values
up section. This suggests a possible causal relation between the ash deposition
and the carbon isotope record, as diminished primary productivity is typified by
negative δ13C TOC values. These results indicate that North-Atlantic volcanism had
significant repercussions and could have played a role in the termination of the PETM. |
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