Architecture of Oxfordian coral buildups along the Atlantic margin of Morocco

Aude Marie Luce Fran Duval-Arnould, Luc Georges Bulot, Rémi Charton, Sreepat Jain, Moussa Masrour, Luis Pomar, Jonathan Redfern, Mike Simmons, Stefan Schröder

Research output: Contribution to journalArticlepeer-review

Abstract

Oxfordian (Upper Jurassic) coral buildups developed widely in Tethys and Atlantic realms, during a time when paleoclimate potentially swung between greenhouse climate and cold snaps. Buildups were constructed by platy and branching corals, sponges and microbialites. Although their initiation is commonly linked to the Upper Jurassic global transgression, a number of global and local factors may have influenced buildup growth and demise (e.g. climate, shelf geometry, detrital input). Extensive outcrops of Oxfordian buildups in Morocco provide an opportunity to investigate the relationship between external drivers and buildup fauna and architecture. Here we show that the interplay of local accommodation changes, rising sea water temperature, and increasing pCO2 linked to the onset of the Middle Oxfordian global transgression were the main drivers for buildup initiation, which was synchronous across the basin. The demise of the coral buildups in Morocco was linked to a regression, dated no later than Upper Oxfordian, the establishment of partly evaporitic conditions across the basin, and to localized influx of coarse-grained siliciclastics, the latter likely driven by synsedimentary tectonic activity. Serial logged sections, outcrop panoramas and detailed facies analysis show that low-relief deeper-water buildups of Dimorpharaea platy corals evolved into higher-relief diversified buildups where shallower-water reworking produced coral rubble and large clinoforms. Buildup diachronicity is apparent, with younger coral bioherms growing in the depressions created between the initial bioherms. Size of buildups ranges from 2 m wide and 0.5 m thick, to 700 m wide and 80 m thick. The outcrops provide constraints on geobody architecture and heterogeneity in the subsurface of Morocco and North America, where facies-controlled dolomitization of high-energy buildup and clinoform facies is a main driver for porosity development.
Original languageEnglish
Article number105206
JournalJournal of African Earth Sciences
Volume213
Early online date26 Mar 2024
DOIs
Publication statusPublished - May 2024

Keywords

  • Coral buildup
  • Oxfordian
  • Platy coral
  • Reef architecture
  • Subsurface analog

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