8 research outputs found
Episodic sedimentation on a peri-Tethyan ridge through the Middle–Late Jurassic transition (Villány Mountains, southern Hungary)
The Villa´ny area, as a central part of the Tisza
microcontinent/terrane along the European margin of
Tethys, was characterized by intense subsidence in the
Early and Middle Triassic, followed by a long interruption
of subsidence in the Late Triassic to Middle Jurassic.
During the Middle–Late Jurassic transition, marine sedimentation
started with three distinct sedimentary episodes
dated as Late Bathonian, Early Callovian, and Middle–Late
Callovian, respectively. The succession is terminated by a
thick limestone of Middle Oxfordian age. The sedimentary
features, microfacies, and macroinvertebrate associations
of these four stratigraphic units are documented and illustrated.
The Middle to Late Jurassic sedimentary episodes of
the Villa´ny succession record an interplay of local and
global factors and paleogeographical changes. At the
beginning, local tectonic movements governed the main
features of sedimentation, though the role of eustasy was
also essential. From the mid-Callovian onwards, global
climatic, biotic, and paleoceanographical changes controlled
the nature and formation of the local carbonate
sediments. The Callovian stromatolites are attributed to the
activity of sulphate-reducing bacteria in a deep sublittoral,
current-swept environment. Upwelling of eutrophic Tethyan
waters is recorded by the prevalence of the Bositra
filament microfacies in the Callovian. The long submarine
hiatus at around the Callovian–Oxfordian transition mirrors
a serious restriction of the carbonate budget, due to sudden
cooling and a change in the oceanic current system
(opening of a circumglobal Tethyan Passage), and to a
higher amount of dissolved CO2. In the Middle Oxfordian,
the carbonate production considerably increased in accordance
with the sudden global warming