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| Titel |
A massive input of coarse-grained siliciclastics in the Pyrenean Basin during the PETM: the missing ingredient in a coeval abrupt change in hydrological regime |
| VerfasserIn |
V. Pujalte, J. I. Baceta, B. Schmitz |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 12 ; Nr. 11, no. 12 (2015-12-11), S.1653-1672 |
| Datensatznummer |
250117488
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| Publikation (Nr.) |
 copernicus.org/cp-11-1653-2015.pdf |
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| Zusammenfassung |
| The Paleocene–Eocene thermal maximum (PETM) is
represented in numerous shallow and deep marine sections of the
south–central and western Pyrenees by a 2–4 m thick unit (locally up to
20 m) of clays or marly clays intercalated within a carbonate-dominated
succession. This unit records a massive input into the Pyrenean Gulf of
fine-grained terrestrial siliciclastics, attributed to an abrupt
hydrological change during the PETM. However, the nature of such a change
remains controversial. Here we show that, in addition to fine-grained
deposits, large volumes of coarse-grained siliciclastics were brought into
the basin and were mostly accumulated in incised valleys and in a long-lived
deep-sea channel. The occurrence of these coarse-grained deposits has been
known for some time, but their correlation with the PETM is reported here
for the first time. The bulk of the incised valley deposits in the PETM
interval are cross-bedded sands and pebbly sands, almost exclusively made of
quartz. The criteria for indicting a relation to the PETM include their
stratigraphic position between upper Thanetian and lower Ilerdian marine
carbonates, organic carbon isotope data, and a high percentage of kaolinite
in the clay matrix. The axially flowing deep-sea channel existed throughout
Paleocene times in the Pyrenean Basin, within which coarse-grained
calciclastic and siliciclastic turbidites were accumulated. This Paleocene
succession is capped by thickly bedded quartz sandstones and pebbly
sandstones, probably deposited by hyperpycnal flows, which are here assigned
to the PETM based on their stratigraphic position and organic carbon
isotopic data. The large and simultaneous increase in coarse- and
fine-grained terrestrial siliciclastics delivered to the Pyrenean Gulf
during the PETM is attributed to an increased intra-annual humidity
gradient. During the PETM a longer and drier summer season facilitated the
erosion of landscapes, whereas a dramatic enhancement of precipitation
extremes during the wet season led to intensified flood events, with rivers
carrying greater volumes of both bed and suspended loads. This scenario
argues against the possibility that PETM kaolinites indicate a coeval warm
and humid climate in northern Spain. Instead, the kaolinite reflects the
erosion of thick Cretaceous lateritic profiles developed on the Hercynian
basement. |
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