Facies associations and evolution of pelagic carbonate platform/basin systems: examples from the Italian Jurassic

Abstract

During the structural and sedimentological evolution of rifted continental margins in carbonate dominated settings, a characteristic stage is commonly reached when pelagic carbonate sedimentation occurs in association with complex fault block systems. An integrated study of the ammonite biostratigraphy and sedimentology of Jurassic pelagic rocks in the Umbria‐Marche Apennines (central Italy) and in the Sila Mountains (north‐east Calabria, southern Italy) has revealed three distinctive facies associations which can be related to specific structural and depositional settings. The condensed pelagic facies association is the constituent of condensed, usually discontinuous sequences, with numerous hiatal surfaces. The normal and resedimented pelagic facies association is typical of thicker sequences, comprising gravity flow and rockfall deposits. The composite pelagic facies association is one in which rockfall deposits are found associated with condensed sequences containing minor or no gravity flow deposits. Palaeotopographical highs are dominated by the condensed pelagic facies association and constitute the pelagic carbonate platform (PCP). Structurally, the PCP can be coincident with the top of a horst (or ‘central high’) block or the crestal area of a tilted block. In the latter case, the sediment surface of the PCP slopes gently (maximum of 1–3°) in this, the shallowest area of a pelagic carbonate ramp. PCPs can have erosional, bypass (rare) and depositional margins. Stepped margins also exist as subparallel rows of erosional and bypass margins. Trends from erosional to depositional margins are usually seen as a response to basin filling and burial of submarine tectonic escarpments by pelagic deposits in late synrift or early post‐rift times. This is apparent from ‘progradation’ of PCP facies deposits beyond the structural boundaries of the PCP. Palaeoenvironmental analysis in pelagic carbonate platform deposits of the Umbria‐Marche Apennines suggests that drowning of ancestral peritidal carbonate platforms in Pliensbachian time was followed first by a moderate deepening and then by shallowing in the Tithonian.

The Middle Jurassic Alpine Tethyan Unconformity and the Eastern Sardinia - Corsica Jurassic High: A sedimentary and regional analysis

“…In the Calabrian arc, a Mesozoic key succession has been described in the Longobucco Group (Triassic-Jurassic boundary to Toarcian) (Young et al, 1986;Bouillin et al, 1988;Santantonio, 1993;Santantonio, 2012;Passeri et al, 2014). This succession evidences sedimentation on a rifted continental margin.…”

“…Furthermore, after Middle Jurassic times, the entire area suffered a rapid collapse (Bourbon et al, 1973), as revealed by the Up-ria-Peloritani terrain was closer to the Alpine Tethys oceanic ridge than the E Sardinia-Corsica high. A further Toarcian extensional phase is mentioned by Santantonio (1993Santantonio ( , 2012. Accordingly, the Alpine Tethyan unconformity is easily recognizable, and the evidence of active extensional tectonics is clear and well-developed along the entire E SardiniaCorsica-Brianconnais ridge.…”

“…It passes first to blackish limestones of the carbonate shelf (Sinemurian), then to marls of the shelf-edge or slope facies (Pleinsbachian), and, finally, to basinal turbidites with intercalated hemipelagites (Pleisnbachian-Toarcian). Santantonio (1993Santantonio ( , 2012 described Toarcian extensional tectonics in the Caloveto Group, close to the Longobucco basin. The lateral setting of the mentioned deposits is probably due to a tilted block system that was similar to those that can be observed on continental passive margins.…”

Oxfordian neptunian dykes with brachiopods from the southern part of the Kraków-Częstochowa Upland (southern Poland) and their links to hydrothermal vents

“…The formation of such fissures is interpreted as an effect of: (1) depositional processes, (2) synsedimentary features, (3) diagenetic transformations of sediments, and, above all, (4) extensional tectonics in the sedimentary basin (see e.g., Land and Goreau 1970;Wendt 1971;Smart et al 1988;Martire 1996;Winterer et al 1991;Santantonio 1993;Winterer and Sarti 1994;Molina et al 1995;Wieczorek and Olszewska 2001;Łuczyński 2001;Flügel 2004;Wall and Jenkyns 2004;Črne et al 2007;Montenat et al 2007;Kandemir and Yilmaz 2009;Kołodziej et al 2010;Reolid and Molina 2010;Nieto et al 2012;Barski 2012).…”

Carbonate-clastic sediments of the Dudziniec Formation in the Kościeliska Valley (High-Tatric series, Tatra Mountains, Poland): role of syndepositional tectonic activity in facies development during the Early and Middle Jurassic

“…The pre vail ing extensional re gime led to dis in te gra tion of Tri as sic car bon ate plat forms oc cu py ing the north ern shelf of the Tethys Ocean and to for ma tion of fault-bounded blocks, which were sub jected to up lift or sub si dence (Michalík, 1994;Wieczorek, 1995;Dumont et al, 1996;Santantonio and Carminati, 2011;Plašienka, 2012). Symp toms of Ju ras sic syndepositional tec tonic ac tiv ity are best known from the Alps (Winterer and Boselini, 1981;Blendinger, 1984Blendinger, , 1986Bertok et al, 2011) and the Apennines (Santantonio, 1993;Cozzi, 2000;Ma rino and Santantonio, 2010). Ju ras sic de pos its of the Tatra Moun tains also show much ev i dence of such ac tiv ity (Uchman, 1994;£uczyñski, 2001a, 2002Jach, 2007;Jezierska and £uczyñski, 2016).…”