Towards a new understanding of the genesis of chalk: Diagenetic origin of micarbs confirmed by clumped isotope analysis
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Towards a new understanding of the genesis of chalk : Diagenetic origin of micarbs confirmed by clumped isotope analysis. / Tagliavento, Mattia; John, Cédric M.; Anderskouv, Kresten; Stemmerik, Lars.
In: Sedimentology, Vol. 68, No. 2, 02.2021, p. 513-530.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Towards a new understanding of the genesis of chalk
T2 - Diagenetic origin of micarbs confirmed by clumped isotope analysis
AU - Tagliavento, Mattia
AU - John, Cédric M.
AU - Anderskouv, Kresten
AU - Stemmerik, Lars
PY - 2021/2
Y1 - 2021/2
N2 - Chalk is usually thought to be a homogeneous sediment with a relatively simple early diagenetic history. Here, clumped isotope analyses of samples from a core of Campanian Maastrichtian chalk are presented, indicating that material smaller than 5 µm has a different origin than the coccolith-dominated coarser fraction. The smallest size fraction (1 to 5 µm) of chalk is dominated by calcite particles without a distinct morphology (micarbs). Clumped isotope data of the micarbs reveals formation temperatures of 14 to 18°C which is 8 to 10°C colder than those derived from coeval coccoliths. The micarbs are interpreted as the product of calcite neoformation, precipitated in the uppermost part of the sediment column (100 metres below sea floor) and linked to early dissolution of aragonitic fossils. These findings prove that early cements can be an abundant component in chalk, and thus challenge the common notion that chalk is always largely composed of calcareous nannofossils, and differs only in terms of minor constituents and degree of lithification.
AB - Chalk is usually thought to be a homogeneous sediment with a relatively simple early diagenetic history. Here, clumped isotope analyses of samples from a core of Campanian Maastrichtian chalk are presented, indicating that material smaller than 5 µm has a different origin than the coccolith-dominated coarser fraction. The smallest size fraction (1 to 5 µm) of chalk is dominated by calcite particles without a distinct morphology (micarbs). Clumped isotope data of the micarbs reveals formation temperatures of 14 to 18°C which is 8 to 10°C colder than those derived from coeval coccoliths. The micarbs are interpreted as the product of calcite neoformation, precipitated in the uppermost part of the sediment column (100 metres below sea floor) and linked to early dissolution of aragonitic fossils. These findings prove that early cements can be an abundant component in chalk, and thus challenge the common notion that chalk is always largely composed of calcareous nannofossils, and differs only in terms of minor constituents and degree of lithification.
KW - Chalk
KW - clumped isotopes
KW - early diagenesis
KW - micarbs
U2 - 10.1111/sed.12802
DO - 10.1111/sed.12802
M3 - Journal article
AN - SCOPUS:85096989381
VL - 68
SP - 513
EP - 530
JO - Sedimentology
JF - Sedimentology
SN - 0037-0746
IS - 2
ER -
ID: 258779886