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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

Pujalte, V.; Baceta, J. I. and Schmitz, Birger LU (2015) In Climate of the Past 11(12). p.1653-1672
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Climate of the Past
volume
11
issue
12
pages
1653 - 1672
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • wos:000367351500005
  • scopus:84949812905
ISSN
1814-9332
DOI
10.5194/cp-11-1653-2015
language
English
LU publication?
yes
id
c9b99568-a741-4923-9916-23df7d484a78 (old id 8767674)
date added to LUP
2016-02-22 10:47:04
date last changed
2017-10-22 03:20:53
@article{c9b99568-a741-4923-9916-23df7d484a78,
  abstract     = {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.},
  author       = {Pujalte, V. and Baceta, J. I. and Schmitz, Birger},
  issn         = {1814-9332},
  language     = {eng},
  number       = {12},
  pages        = {1653--1672},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Climate of the Past},
  title        = {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},
  url          = {http://dx.doi.org/10.5194/cp-11-1653-2015},
  volume       = {11},
  year         = {2015},
}