Relief development of a Mesozoic carbonate platform margin (Southern Alps, northern Italy)

Abstract

AbstractThe effect of various erosional processes on the relief development of a carbonate platform margin is documented from outcrops of the Southern Alps, northern Italy, by the occurrence of truncation surfaces and redistribution of remobilized sediments. The periplatform depositional history, with periods of intensive submarine erosion along the north‐western Trento plateau margin, is recorded by various carbonate deposits ranging in age from the Early Jurassic to Late Cretaceous with numerous gaps.The first Early Jurassic period of submarine erosion is marked by truncation and extensive tectonic fracturing of lower Liassic oolitic skeletal periplatform deposits. These are overlain by pelmicritic sediments of late Hettangian to Toarcian age. The second period of submarine erosion during the late Early Jurassic resulted in almost complete truncation of the pelmicritic unit. Crinoidal to oolitic periplatform carbonate sands were subsequently deposited along the carbonate margin until the Aalenian/Bajocian. The third truncation surface was produced by partial current erosion of the crinoidal to oolitic periplatform deposits during the late Bajocian to Callovian. The fourth, and most prominent, truncation surface was produced by erosion during the Early Cretaceous cutting down from Aptian/Albian pelagic units to Toarcian periplatform deposits. The resulting submarine relief was completely buried during the late Maastrichtian by onlapping pelagic sediments.The documentation of the depositional history during the Late Mesozoic of the north‐western Trento plateau pinpoints the main mechanisms responsible for the relief of the drowned carbonate platform margin. Extensional tectonic activity during differential subsidence and current‐induced erosional truncation, followed by gravitational downslope mass transport and rapid pelagic burial mainly determined the morphology of the drowned carbonate platform margin.