Search

Direct observations from the geologic record are commonly used in conjunction with indirect seismic inferences to detail environmental settings and stratal architecture of sedimentary successions. However, examples of integration between seismic and macrobenthic insights are scarce and limited to the use of such a group as an auxiliary to other proxies. We investigated mollusc and ostracod assemblages along an onshore-offshore transect that intersects the C-2 clinothem (15.6 - 14.4 ka BP) and the overlying transgressive deposits that recorded the last phase of progradation and abandonment of the Po River Lowstand Wedge (PRLW). We applied multivariate analyses to benthic data to assess the extent to which mollusc and ostracod assemblages can improve both the resolution of seismic-derived depositional environments and the sequence stratigraphic architecture of targeted sedimentary succession. Along the onshore-offshore transect, seismic reflection geometries correspond with three broad sedimentary environments: High Amplitude Continuous reflections (HAC) are interpreted as delta plain/subaqueous shelves, High Amplitude Continuous Wavy Dipping reflections (HACWDip) as prodeltas and Low Amplitude Continuous reflections (LAC) are associated to distal basin settings. The integration of quantitative palaeoecologic trends with seismic-derived depositional environments allowed us to subdivide the HAC facies into a proximal (core LSD-26) and distal (cores LSD-27 and -28) area. The proximal HAC facies, in particular, encompasses lower delta plain semi-barred settings with vegetated substrates that upcore pass to nearshore settings. The distal HAC facies is distinguished by clusters that suggest ecological mixing due to strong bioturbation and wave-aided hyperpycnal flows in offshore transition/inner shelf settings. The paucity of benthic fauna for the geophysical units HACWDip (core LSD-05) and LAC (core LSD-04) hampered a complete reconstruction of the palaeoenvironmental dynamics. However, both benthic groups support a seismically derived interpretation of shelf and basinal settings, respectively, and both were subjected to high sedimentation rates. Moreover, integration of mollusc and ostracod multivariate-derived trends with grain-size data across the onshore-offshore transect reveals distinctive stratal stacking patterns that are useful in constraining the position of the Maximum Regressive Surface that marks the abandonment of the PRLW in the Central Adriatic Sea.

In the recent years, a large amount of marine geophysical data has been acquired along the Italian continental margins. Geophysics techniques such as multibeam and high-resolution sub-bottom profiles have been particularly useful in the reconstruction of the recent and active processes whose traces are found both at the seafloor and in the upper stratigraphy of slope and basin. In this chapter, we present a review of the available studies on a suite of submarine landslides along two portions of the Italian seas. The study areas are in the southwestern Adriatic Sea and in the southeastern Tyrrhenian Sea. Submarine landslides have been investigated through the analysis of their seafloor morphology and their internal architecture. Our study gives a detailed insight, from a marine geology perspective, on the large variety of internal geometry and features that characterize the deposits associated with submarine landslides. This chapter emphasizes the importance of the fine-scale characterization of the range of elements within the different sectors of mass-transport deposits. The recognition and the comprehension of these elements are crucial for a better definition of the controlling factors that drive the final arrangement of failed sediments.

Despite intense research by both academia and industry, the parameters controlling slope stability at continental margins are often speculated upon. Lack of core recovery and age control on failed sediments prevent the assessment of failure timing/frequency and the role of prefailure architecture as shaped by paleoenvironmental changes. This study uses an integrated chronological framework from two boreholes and complementary ultrahigh-resolution acoustic profiling in order to assess (1) the frequency of submarine landsliding at the continental margin of NE Gela Basin and (2) the associated mechanisms of failure. Accurate age control was achieved through absolute radiocarbon dating and indirect dating relying on isotope stratigraphic and micropaleontological reconstructions. A total of nine major slope failure events have been recognized that occurred within the last 87 kyr (~10 kyr return frequency), though there is evidence for additional syndepositional, small-scaled transport processes of lower volume. Preferential failure involves translational movement of mudflows along subhorizontal surfaces that are induced by sedimentological changes relating to prefailure stratal architecture. Along with sequence-stratigraphic boundaries reflecting paleoenvironmental fluctuations, recovered core material suggests that intercalated volcaniclastic layers are key to the basal confinement and lateral movement of these events in the study area. Another major predisposing factor is given by rapid loading of fine-grained homogenous strata and successive generation of excess pore pressure, as expressed by several fluid escape structures. Recurrent failure, however, requires repeated generation of favorable conditions, and seismic activity, though low if compared to many other Mediterranean settings, is shown to represent a legitimate trigger mechanism.