[Show abstract][Hide abstract] ABSTRACT: This paper gives a detailed description of the use of minor structures on fault planes in various brittle rocks as indicators of the sense of relative movement. The main kinds of structures described involve sets of repeated secondary fractures (striated or not) which intersect the slip plane in a direction roughly perpendicular to the slip direction. Some of the most frequent criteria are new; their reliability is established in the field and by comparison with both previous and new experiments. It is shown that some of the rarer structures probably correspond to neo-rupture in intact rock, most probably at the tip of pre-existing joints, while the most frequent structures are generated by friction on joints, with very little sliding. The possible seismic origin of some structures is discussed.
[Show abstract][Hide abstract] ABSTRACT: An extensive study of the ammonoid fauna occurring in the lagoonal facies of a Middle Triassic isolated carbonate platform (Latemar platform, Dolomites, Italy) has been undertaken, and ammonoids from selected coeval successions (Punta Zonia, Marmolada, Rio Sacuz) have been illustrated. Ammonoids from Latemar have been collected in 20 distinct horizons (storm deposits) within the ca. 500 m thick lagoonal succession of the platform, thus providing a biostratigraphy of a series which is unusually expanded for this time interval, close to the Anisian–Ladinian boundary. Contrary to general opinion, some ammonoids of the Latemar and other coeval carbonate platforms of the Dolomites (Marmolada, Cernera), in particular Aplococeras avisianum, Lecanites misanii, Celtites spp., and Paranevadites sp., are also present in nearby basinal series. The same taxa have been found in North American localities deposited at the opposite margin of Panthalassa. The homotaxis of these ammonoids in North America and Latemar allow to establish a global scale correlation between the Southern Alps and North America with the highest resolution to date possible. In the context of this study, Aplococeras transiens n. sp. and Esinoceras nerinae n. sp are established.
[Show abstract][Hide abstract] ABSTRACT: As a result of a phase of extensional tectonics in the western Tethyan region, a horst and graben topography formed. Horsts were sites of shallow water carbonate sedimentation, while pelagic and volcaniclastic sediments were deposited in the grabens. Two carbonate platforms approximately 500 m thick can be distinguished. The facies of these isolated platforms reflect the influence of storms from the SW. The stationary platform type can be distinguished from a retrograding type, whereas continuously prograding platforms apparently did not develop. -from Author
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