ABSTRACT

The Caloveto area in northeastern Calabria hosts a stratigraphic succession which documents the evolution from shallow water carbonates to deeper-water pelagic and hemipelagic deposits, bearing ample evidence for severe tectonic control on Jurassic and Early Cretaceous sedimentation. Geological mapping indicates that the shallow-water carbonates, also with coral assemblages, formed a narrow fringe around a high of the Hercynian basement, made of low-grade metamorphic rock, which remained emergent throughout the Pliensbachian and became an intrabasinal high of the Longobucco basin, hosting thin pelagic sedimentation during most of the Jurassic. An extensional phase in the Toarcian disrupted and foundered the benthic carbonate factory, whose drowning is documented by a change to Rosso Ammonitico-type deposits. This resulted in a complex network of neptunian dykes (also intruding the basement) and in-situ breccias. Starting in the late Toarcian, the rugged submarine topography was gradually leveled by onlapping marls, radiolarites and pelagic limestone, which sealed the Toarcian fault zones producing a diverse array of unconformities. Colonization by microbial communities characterizes the initial stages of marine sedimentation around the cores of Paleozoic basement, as banded polychrome microbialites and “swollen” phyllites, a result of the microbially-influenced/induced displacive growth of calcium carbonate crystals along split cleavage planes, constitute an unexpected field tool for identifying basin margins. Silicified marginal zones in the shallow water limestone characterize, analogous to other Tethyan regions, the onlap unconformities of chert-rich basinal units on the submerged carbonate fringes.

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