Review of earliest Toarcian geological evolution in the East African Coastal Margin: Paleogeography, stratigraphy, and facies implications

Gama, John ✉; Schwark, Lorenz

Angol nyelvű Összefoglaló cikk (Folyóiratcikk) Tudományos
Megjelent: JOURNAL OF AFRICAN EARTH SCIENCES 1464-343X 1879-1956 200 Paper: 104885 , 18 p. 2023
  • X. Földtudományok Osztálya: A
  • SJR Scopus - Earth-Surface Processes: Q2
Azonosítók
Szakterületek:
  • Föld- és kapcsolódó környezettudományok
In the past decades, lower Toarcian strata have gained attention on a global paleogeographical scale but these strata have been poorly studied along the East African Margin. This study presents a comprehensive review of the Toarcian geological evolution of the East African Coastal Margin focusing mainly on the Mandawa Basin in Tanzania, the Morondava and Majunga Basins in Madagascar, the Lamu and Mandera Basins in Kenya, and the Luuq Mandera and Ahl-Mado Basins in Somalia. We discuss controversies in published reports regarding facies, stratigraphy, and pathways of marine ingressions during the Toarcian transgressive episode that led to the extension of a Neotethys sea arm (the Somali Ocean) into the East African Margin prior to the main phase of Gondwana drifting and the opening of the Indian Ocean.The earliest Toarcian transgressive phase was accompanied by rifting between East Africa and Madagascar, which most likely rejuvenated Karoo rifting, drove marine influxes and inundated existing depressional troughs in the Ahl-Mado, Luuq Mandera, SW Majunga, and Mandawa Basins. This resulted in the formation of the Arab-Indo-Madagascar embayment, a NNE-SSW striking epicontinental sea (Somali Ocean), which was linked to the Tethys Sea southward via the horn of Africa route, as well as in widespread deposition of Toarcian marine to coastal-lagoonal to continental sediments. The occurrence of major facies changes from predominantly conti-nental to shallow/marginal marine facies and the widespread distribution of an Arab-Indo-Madagascan Bou-leiceras ammonite association confirms the connection between the East African coastal sedimentary terrain and the Tethys Sea during the Toarcian. Influxes of marine waters from Tethys Sea were limited in extent to the rift -graben regions and reactivated Karoo faults system. Restricted marine deposition within a limited epicontinental sea likely ended during Late Aalenian-Bajocian times, when establishment of fully marine conditions began due to opening of the Indian Ocean.
Hivatkozás stílusok: IEEEACMAPAChicagoHarvardCSLMásolásNyomtatás
2025-02-18 20:18