The Early Cretaceous drowning unconformities of the Apulia carbonate platform (Gargano Promontory, southern Italy): local fingerprints of global palaeoceanographic events.

Abstract

Drowning successions which cap carbonate platforms and flanks bear palaeoenvironmental information which is useful for genetic stratigraphy; they constitute predictive key‐markers in regional to global correlations. An Early Cretaceous platform‐to‐basin transition has been investigated in Apulia (southern Italy) and two drowning unconformities, dated as early Valanginian and late early Aptian, have been documented. They occur at the base of thick pelagic tongues wedging toward the platform and mark the base of two depositional sequences showing distinct transgressive–regressive cycles. Timing of drowning processes, based on biostratigraphy and dynamic stratigraphy, allows the correlation of unconformities with global‐scale palae‐ oceanographic events marked, among others, by positive spikes of well‐established δ13C curves. Drowning signatures in the Apulia carbonates fit the stratigraphic, palaeoecological and possibly geochemical evidence found in global records at the same stratigraphic levels. Moreover, it is proposed that the observed drowning events were caused by palaeoceanographic crises affecting factory productivity.

Internal architecture of mass‐transport deposits in basinal carbonates: A case study from southern Italy

“…The southern part of the Gargano Promontory is well‐known for its spectacular deposits of platform‐slope limestones that form large megabreccias containing shallow‐water lithoclasts supported by finer‐grained, shallow‐marine bioclastic grainstones and foraminifera mudstones (Morsilli & Bosellini, ; Bosellini et al ., ; Graziano, ; Hairabian et al ., ). These deposits are regarded as the product of repeated collapse of the platform margin, possibly induced by synsedimentary extensional faulting (Graziano, , ; Borgomano, ).…”

Rudists and carbonate platforms in the Aptian: a case study on biotic interactions with ocean chemistry and climate

“…These authors accordingly suggested that these latter regions had escaped the effects of eutrophication fuelled by enhanced continental weathering which, according to their model, had caused the demise of the northern platforms. Yet this model left two key points unexplained: firstly, the evidence that OAE 1a also affected facies on the isolated Apulian Platform and even on such remote oceanic platforms as Resolution Guyot, in the Pacific (Graziano, 1999; Jenkyns & Wilson, 1999), not just those close to continental hinterlands; and, secondly, the mass extinction of platform biota recorded by Masse (1989) reached its finale at the end, not the middle of the Early Aptian (Fig. 2) – an observation that has stood the test of subsequent biostratigraphical refinement (Masse, 2003).…”

Calcareous nannofossil response to the Weissert episode (Early Cretaceous): Implications for palaeoecological and palaeoceanographic reconstructions

“…The Valanginian nannoconid decline occurred before and throughout the first major perturbation in the Cretaceous carbon cycle, the so-called "Weissert Event" or episode Charbonnier et al, 2013) defined by a global positive excursion, in marine carbonate-and marine and terrestrial organiccarbon isotope records (Cotillon and Rio, 1984;Lini et al, 1992;Channell et al, 1993;Föllmi et al, 1994;Weissert et al, 1998;Hennig et al, 1999;Wortmann and Weissert, 2001;Gröcke et al, 2005;Duchamp-Alphonse et al, 2007;Bornemann and Mutterlose, 2008). It coincided with several phases of carbonate platform drownings (Schlager, 1989;Föllmi et al, 1994;Graziano, 1999;Föllmi et al, 2006) and overall turnovers and crises in pelagic and neritic carbonate biota (Channell et al, 1993;Kaim, 2001;Bersezio et al, 2002;Janssen and Clément, 2002;Erba and Tremolada, 2004;Duchamp-Alphonse et al, 2007;Barbarin et al, 2012). Interestingly, no widespread anoxia is observed (Westermann et al, 2010;Kujau et al, 2012), although sometimes, black shales are found in the Tethys and Pacific Oceans .…”