In the Neka Valley (Eastern Alborz, Iran), glaucony-bearing marine sediments of early-middle Santonian age directly overlie Palaeozoic to Triassic units deformed during the Eo-cimmerian orogenic event (Late Triassic). The Upper Cretaceous open marine sediments were deposited on a flat surface lacking any evidence of pedogenesis. The geochemical and morphological features of glaucony grains, that characterize the base (1 to 1.5 m) of the Upper Cretaceous succession, indicate an autochthonous origin of the highly-evolved glaucony, denoting a long-lasting period of low sedimentation rate. The development of glaucony in the observed stratigraphic position is indicative of a rapid drowning of the former Cimmerian relief that can not be explained by an eustatic rise alone: the palaeo-depth needed for the development of glaucony and for the presence of the observed bathial foraminifera assemblages is greater than the maximum eustatic excursion documented in the Cretaceous. The occurrence of glaucony in this stratigraphic position reflects thus an important episode of increased subsidence rates, related to a geodynamic event framed in a time-interval of major plate reorganization in the complex puzzle of the Iranian plates: the subsidence event that caused the development of the glauconitic horizon in the Neka Valley could likely represent the effect of a Santonian stage of the complex and long-lasting story of the opening of the Caspian Sea.

Late Cretaceous transgression on a Cimmerian high (Neka Valley, Eastern Alborz, Iran): a 2 geodynamic event recorded by glauconitic sands / F. Berra, A. Zanchi, M. Mattei, A. Nawab. - In: SEDIMENTARY GEOLOGY. - ISSN 0037-0738. - 199:3-4(2007 Jul 15), pp. 189-204.

Late Cretaceous transgression on a Cimmerian high (Neka Valley, Eastern Alborz, Iran): a 2 geodynamic event recorded by glauconitic sands

F. Berra
Primo
;
2007

Abstract

In the Neka Valley (Eastern Alborz, Iran), glaucony-bearing marine sediments of early-middle Santonian age directly overlie Palaeozoic to Triassic units deformed during the Eo-cimmerian orogenic event (Late Triassic). The Upper Cretaceous open marine sediments were deposited on a flat surface lacking any evidence of pedogenesis. The geochemical and morphological features of glaucony grains, that characterize the base (1 to 1.5 m) of the Upper Cretaceous succession, indicate an autochthonous origin of the highly-evolved glaucony, denoting a long-lasting period of low sedimentation rate. The development of glaucony in the observed stratigraphic position is indicative of a rapid drowning of the former Cimmerian relief that can not be explained by an eustatic rise alone: the palaeo-depth needed for the development of glaucony and for the presence of the observed bathial foraminifera assemblages is greater than the maximum eustatic excursion documented in the Cretaceous. The occurrence of glaucony in this stratigraphic position reflects thus an important episode of increased subsidence rates, related to a geodynamic event framed in a time-interval of major plate reorganization in the complex puzzle of the Iranian plates: the subsidence event that caused the development of the glauconitic horizon in the Neka Valley could likely represent the effect of a Santonian stage of the complex and long-lasting story of the opening of the Caspian Sea.
glaucony ; Late Cretaceous ; Cimmerian Orogeny ; Alborz, unconformity
Settore GEO/02 - Geologia Stratigrafica e Sedimentologica
15-lug-2007
Article (author)
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/23784
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 26
  • ???jsp.display-item.citation.isi??? 26
social impact