Microfacies and composition of ferruginous beds at the platform-foreland basin transition (Late Albian to Turonian Natih Formation, Oman Mountains): Forebulge dynamics and regional to global tectono-geochemical framework

Frank Mattern*, Bernhard Pracejus, Andreas Scharf, Gianluca Frijia, Moath Al-Salmani

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Two forebulge successions exist in the Oman Mountains at the platform-foreland basin transition between the Late Albian to Turonian Natih Formation and the foreland basin shales of the Late Cretaceous Muti Formation. Forebulge creation is suggested by limestone microfacies analyses and analyses of ferruginous crusts and oolites, showing rapid changes in bathymetry and relative sedimentation rate. Each succession displays basal shallow subtidal limestone, passing upward directly to ferruginous crusts and then to Fe-rich oolites deposited in shallower and agitated water. Each succession is topped by clayey layers. Microfacies and lithological evolution of the two successions are alike, suggesting repetitively similar depositional and tectonic conditions. As both sequences occur at the same site, lateral forebulge migration possibly did not occur, suggesting an overall stationary vertical and stepwise forebulge development. The compositional evolution of the ferruginous crusts was complex and includes postdepositional diagenetic effects of the rocks. Both ferruginous crusts once consisted of iron sulfides, implying at least slightly reducing conditions during their formation, associated with water-deepening events. Both oolite levels contain chlorite, hematite, quartz, calcite and apatite. They also contain fragments of chlorite and hematite as nuclei, suggesting that these fragments derived from preexisting ferruginous crusts. Iron oxyhydroxides and clinochlore within the oolites reflects bathymetric changes to more oxidizing aqueous conditions, associated with water-shallowing events. Fe-rich anoxic to sub-oxic sea water of the marine foreland basin was the source for the crusts and oolites which coincided with a high rate of global Cretaceous ocean crust production and related hydrothermalism as well as the regional proximity of an active spreading axis. Fe was probably stabilized in ocean water as organic Fe complexes and Fe colloids.

Original languageEnglish
Article number106074
JournalSedimentary Geology
Volume429
DOIs
Publication statusPublished - Mar 1 2022
Externally publishedYes

Keywords

  • Aruma Foreland Basin
  • Ferruginous crusts
  • Ferruginous oolites
  • Forebulge sequences
  • Gamma-radiation
  • High oceanic crust production

ASJC Scopus subject areas

  • Geology
  • Stratigraphy

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