Relations between submarine fissures, internal breccias and mass flows during Triassic and earlier rifting periods

Abstract

ZusammenfassungTiefe Spalten in Flachwasserkalken, welche mit Tiefwassersediment gefiillt sind, wurden verschiedentlich beschrieben, besonders aus der Trias und dem Jura der Tethys und aus dem Mitre1-bis Oberdevon des variscischen Orogens. Mass flows kommen in den gleichen Formationen und Gebieten vor. Auf Hydra (Griechenland) konnte gezeigt wetden, dab als Zwischenglied dieser beiden Erscheinungen sogenannte Internbreecien aug treten, deren Karbonatklasten wie Puzzles aneinanderpassen. Sie weisen auf Hang-oder hangnahe Positionen hin und entstehen sehr wahrscheinlich durch flexurartige Deformationen yon Kalken in geringer Versenkungstiefe. ErdbebenstSBe m6gen mit iiberhydrostatischem Druck an der Brecciierung der schwaeh verfestigten Kalksedimente beteiligt sein. So wird Material fiir mass flows bereitgestellt.Diese Vorg~inge sind mit tektonischen Absenkungen verkniipft; die FlachwasserkalkBreccien enthalten oft eine Matrix yon Sedimenten tieferen Wassers. Solche Breccien und Spalten entstehen in Gebieten und Perioden mit submarinem ,,rifting", spezieH im Oberdevon und in der Trias. Fi,ir die letztere kSnnen die einzelnen Brecciierungs-Ereignisse yon Griechenland bis zu den Alpen verfolgt werden und entsprechen vermutlich auch gr/SBeren Transgressionen in der germanisehen Trias. AbstractDeep fissures in shallow-water limestones filled with deep-water sediments are described from many places especially in the Triassic and Jurassic of the Tethys and in the Middle to Upper Devonian of the Variscian Mountains. Mass flows occur in the same formations and areas. On the island of Hydra (Greece) it was possible to show that both phenomena are linked by internal breccias of well-fitted limestone fragments. They are indicative of slope or near-slope positions and are very probably caused by flexure-like deformations of shallow-burial limestones. Seismic shocks producing overpressure may be instrumental in the disintegration of the semi-lithified limestones thus providing the material for mass flows.These events are associated with a teetonical subsidence as shown by deep-water matrix in the breceiated shallow-water limestones. They occur in areas and periods of submarine rifting, especially in late Devonian and Triassic time. At least four Triassic brecciation events can be traced from Greece to the Alps and correspond presumably to major transgressions in the eratonic basin of middle Europe. R6sum6Des profondes fissures remplies de s6diments d'eau profonde ont 6t6 d6erites, dans un certain hombre de loealit6s, dans des ealeaires marius de faible profondeur, surtout du Trias et du Jurassique de la M6sog6e, ainsi que du D6vonien moyen et sup6rieur de l'orog6ne hercynien. Des 6eoulements en masse (mass flows) se pr6sentent dans les m6mes formations et r6gions.

Peritidal Carbonate–Evaporite Sedimentation Coeval to Normal Fault Segmentation During the Triassic–Jurassic Transition, Iberian Chain

“…The fragmentation and subsidence of the carbonate platforms in the whole Alpine-Mediterranean region began with the Triassic-Jurassic transition (e.g. Bernoulli & Jenkyns, 1974;Fütchbauer & Ricchter, 1983). Similar to the model reconstructed in the presented case study, Cozzi & Hardie (2003) have reported on normal faulting prior to and at the Triassic-Jurassic boundary in the Carnian Prealps, which was related to a major rifting phase for the northwestern Tethys starting at the middle Norian.…”

Stratabound ore deposits related to synsedimentary tectonics: South-West Sardinia (Italy) and Sierra de Aracena (Spain); a comparison

“…Brecciation is particularly intense in the mineralized areas close to the basin margins. This might indicate a tectonic origin of the breccias (BECHSTADT & BONI, 1989); they might be caused by flexure-like deformations of the platform margin (according to the model of FOCHTBAUER & RICHTER, 1983). Breccias of this type should be more or less stratabound, as can be observed in the mineralized areas.…”

Jurassic unconformities in the High-Tatric succession, Tatra Mountains, Poland

“…12B) is in ter preted as be ing of tec tonic or i gin, and is typ i cal of mar gins of iso lated car bon ate plat forms (Füchtbauer and Rich ter, 1983;Blendinger, 1986;Smart et al, 1988;Šmuc, 2010). Their de vel op ment is as so ci ated with an extensional re gime that pre vailed in the Bajocian in the HighTatric area, and which gen er ally re sulted from palaeo geographi cal changes in the Cen tral Carpathian area.…”

“…Iso lated car bon ate platforms formed on el e vated ar eas, on which con tin u a tion of shallow-wa ter sed i men ta tion took place. The pre vail ing extensional re gime com monly led to the de vel op ment of sub ma rine fis sures filled by ma rine de pos its -nep tu nian dykes, and to the for mation of in ter nal brec cias (Füchtbauer and Rich ter, 1983;Blendinger, 1986;Plašienka, 1995).…”