Intrasediment gypsum in subtidal offshore carbonates as a witness of basin-wide evaporitic precipitation. The case of the southern Variscan foreland basin (mid-Carboniferous)
Articolo
Data di Pubblicazione:
2024
Citazione:
Intrasediment gypsum in subtidal offshore carbonates as a witness of basin-wide evaporitic precipitation. The case of the southern Variscan foreland basin (mid-Carboniferous) / I. Díaz-García, Ó. Merino-Tomé, I.E. Quijada, J.R. Bahamonde, L.P. Fernández, G. Della Porta, E. Samankassou, E.I. Kulagina, Á.G. Borrego, J. Martín-Llaneza, J.F. Del Pozo. - In: SEDIMENTARY GEOLOGY. - ISSN 0037-0738. - 464:(2024), pp. 106605.1-106605.26. [10.1016/j.sedgeo.2024.106605]
Abstract:
Widespread calcite and quartz pseudomorphs, interpreted as originally gypsum crystals, occur within
hemipelagic calci-mudstone accumulated in subtidal offshore environments in the broad marine foreland
basin developed on the southern flank of the Ouachita–Alleghanian–Variscan Orogen during mid-
Carboniferous times,which acted as a marine corridor connecting the Panthalassa and Palaeo-Tethys Oceans during
the Mississippian, and progressively narrowed during the assembly of Pangea. In this study, 67 outcrops of
radiolaria-bearing calci-mudstone deposits that contain calcite and quartz pseudomorphs located in northern
Spain and southern France were studied to constrain the gypsum spatial distribution and sedimentological features.
The recognised microfacies indicate intrasediment gypsum precipitation, accompanied by less abundant
bottom-grown precipitates and gypsum cumulates, in extensive offshore, probably several ten to a few hundred
metres deep, basinal environments. Gypsumprecipitation took place during a short-lived temporal episode during
the early Bashkirian time (Voznesenkian), which can be correlated, on the basis of benthic foraminifera, with
the coastal (inter- to supratidal) gypsum evaporites identified in NW Africa (Tindouf and Reggan successions in
Morocco and Algeria) that would represent the shallow-water counterparts. The occurrence of gypsum precipitates
both in offshore hemipelagic calci-mudstones of the Variscan foreland basin and in inter- to supratidal environments
of the epeiric Sahara Platform indicates that hypersaline conditions affected vast marine areas,
roughly coinciding with the estimated age of closure of the Panthalassa and Palaeo-Tethys marine connection.
Therefore, the studied succession represents the trace of a basin-wide evaporitic episode extending for hundreds
of kilometres driven by foreland basin restriction, mid-Carboniferous sea-level fall and arid climate. This study
provides new insights for the interpretation of gypsum precipitates in offshore marine environments encountered
in the Phanerozoic and whose genesis is poorly understood.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Marine evaporites; Intrasediment gypsum; Carboniferous; Variscan foreland basin
Elenco autori:
I. Díaz-García, Ó. Merino-Tomé, I.E. Quijada, J.R. Bahamonde, L.P. Fernández, G. Della Porta, E. Samankassou, E.I. Kulagina, Á.G. Borrego, J. Martín-Llaneza, J.F. Del Pozo
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