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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 6. (June)

First Page: 793

Last Page: 793

Title: Sedimentary Evolution of Passive Margins of Mesozoic Tethys: ABSTRACT

Author(s): Daniel Bernoulli


The Alpine mountain chains of the Circum-Mediterranean area and the Near East are the result of oblique convergence between Africa and Eurasia. This convergence was, from the Late Triassic to Early Cretaceous, preceded by an oblique divergence during the opening of the Jurassic-Early Cretaceous Atlantic-Tethyan ocean. Rifting and spreading of this ocean are discordantly superimposed onto the preexisting late Paleozoic paleogeography of Pangea and the paleo-Tethys. Kinematic considerations suggest that in the Alpine-Mediterranean area the opening of Tethys was dominated by sinistral transform movements.

Whereas, in the central Atlantic and western Mediterranean area, Late Triassic to Early Jurassic rifting occurred in a continental environment and was accompanied by alkaline volcanicity and evaporite deposition, east of the central Mediterranean the zones of rifting which eventually led to the opening of the oceanic Tethys did not follow the complex pattern of Triassic seaways, but occurred across the marine carbonate belts of the Gondwanian margin of paleo-Tethys. As a consequence, there are hardly any siliciclastic sediments associated with the Early Jurassic phase of rifting, and evaporite deposits of Jurassic age are conspicuously lacking along the rift zone. Depositional geometry of the synrift sediments, at places, suggests listric normal faulting as a possible mechanism of cru tal thinning, and the resulting pattern of tilted fault blocks compares very well with that found along undeformed margins, e.g., the Cretaceous Iberian or Armorican margins. In the Tethys, this rifting phase initiated a new paleogeography along the developing continental margins with Bahamian-type carbonate platforms, submarine plateaus, basins, and marginal highs. With the onset of spreading in the oceanic areas, subsidence rates decreased and were more evenly distributed over the margins; during this stage, subsidence apparently followed a curve of exponential decay. Sedimentary facies of the distal continental margins were then determined by increasing water depth and basin-wide paleo-oceanographic events. This general paleotectonic reconstruction of Tethyan margins is confirmed by c mparable sedimentary facies in undeformed margins of the Mesozoic central Atlantic.

In the Mid-Cretaceous, plate motions in the Atlantic-Tethyan system changed drastically, and sinistral and opening movements in the Mediterranean were replaced by dextral and compressive ones leading to the complete elimination of the oceanic Tethys between the Late Cretaceous and late Eocene.

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