Article (Scientific journals)
A model for the concomitant early formation of dolomite and fibrous clays in coastal bay systems: Evidence from the Eocene (Paris Basin, France)
Talon, Julien; Pellenard, Pierre; Baele, Jean-Marc et al.
2025In Sedimentology, 72 (6), p. 1860-1898
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Keywords :
dolomite; LLTM event; magnesian minerals; microbial influence; palygorskite; Paris Basin
Abstract :
[en] Detailed analysis of Lutetian-Bartonian deposits in the Paris Basin ('Marnes et Caillasses' Formation) provides new evidence of concomitant magnesian fibrous clays (palygorskite and sepiolite) and early microcrystalline dolomite. Although relatively uncommon in sedimentary archives, palygorskite and sepiolite are found in a wide range of environments, from deep-marine to terrestrial. In coastal bay environments, these clay minerals can be formed under arid conditions, either by direct precipitation or by transformation from a precursor, often in association with carbonate. The concomitant formation of fibrous clays and dolomite remains poorly understood until now. Most models consider that fibrous clays form alongside calcite. More recently, it has been suggested that dolomite dissolution can facilitate fibrous clay formation during diagenesis. A new integrative model for concomitant dolomite and fibrous clay formation in coastal marine bay systems is proposed here, based on X-ray diffraction, organic carbon isotopes, electron microscopy, cathodoluminescence, and epifluorescence. In such systems, highly fluctuating hydro-biogeochemical conditions alternately favour the early formation of dolomite or fibrous clays. This study highlights, for the first time, the concomitant presence of three striking processes: (i) microbially influenced microcrystalline dolomite formation; (ii) detrital Al-Fesmectite transformation into palygorskite; (iii) dolomite dissolution, facilitating magnesium availability. These processes are favoured by the warm climate conditions of the Middle Eocene and a progressively restricted coastal bay environment related to regional regression. Based on geochemical and biostratigraphic data, this study also provides the first evidence of the Late Lutetian Thermal Maximum (LLTM) in coastal environments. During the LLTM, increased aridity punctuated by episodic floods linked to intensified runoff further exacerbated the already highly fluctuating hydrobiogeochemical conditions, thus favouring the early formation of dolomite and fibrous clays. These climate conditions, combined with basin confinement linked to Pyrenean deformation, may have facilitated the onset of a significant Eocene fibrous clay episode in NW Europe.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Talon, Julien  ;  Université de Mons - UMONS > Faculté Polytechnique > Service de Géologie fondamentale et appliquée ; Université Bourgogne Europe > Biogéosciences UMR 6282 CNRS/UBE
Pellenard, Pierre;  Université Bourgogne Europe > Biogéosciences UMR 6282 CNRS/UBE
Baele, Jean-Marc  ;  Université de Mons - UMONS > Faculté Polytechnique > Service de Géologie fondamentale et appliquée
Quesnel, Florence;  Bureau de Recherche Géologique et Minières > DCGS
Briais, Justine;  Bureau de Recherches Géologiques et Minières > DCGS
Iakovleva, Alina;  RAS - Russian Academy of Sciences > Geological Institute > Laboratory of Paleofloristics
Dupuis, Christian ;  Université de Mons - UMONS > Faculté Polytechnique > Service de Géologie fondamentale et appliquée
Bruneau, Ludovic;  Université Bourgogne Europe > Biogéosciences UMR 6282 CNRS/UBE
Vennin, Emmanuelle;  Université Bourgogne Europe > Biogéosciences UMR 6282 CNRS/UBE
Language :
English
Title :
A model for the concomitant early formation of dolomite and fibrous clays in coastal bay systems: Evidence from the Eocene (Paris Basin, France)
Publication date :
04 June 2025
Journal title :
Sedimentology
ISSN :
0037-0746
eISSN :
1365-3091
Publisher :
Wiley
Volume :
72
Issue :
6
Pages :
1860-1898
Peer reviewed :
Peer Reviewed verified by ORBi
Research unit :
F401 - Géologie fondamentale et appliquée
Research institute :
R400 - Institut de Recherche en Science et Ingénierie des Matériaux
R200 - Institut de Recherche en Energie
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