Preserving adaptive capacities of coastal ecosystems, which are currently facing the ongoing climate warming and a multitude of other anthropogenic impacts, requires an understanding of long‐term biotic dynamics in the context of major environmental shifts prior to human disturbances. We quantified responses of nearshore mollusk assemblages to long‐term climate and sea‐level changes using 223 samples (~71,300 specimens) retrieved from latest Quaternary sediment cores of the Adriatic coastal systems. These cores provide a rare chance to study coastal systems that existed during glacial lowstands. The fossil mollusk record indicates that nearshore assemblages of the penultimate interglacial (Late Pleistocene) shifted in their faunal composition during the subsequent ice age, and then reassembled again with the return of interglacial climate in the Holocene. These shifts point to a climate‐driven habitat filtering modulated by dispersal processes. The resilient, rather than persistent or stochastic, response of the mollusk assemblages to long‐term environmental changes over at least 125 thousand years highlights the historically unprecedented nature of the ongoing anthropogenic stressors (e.g., pollution, eutrophication, bottom trawling, and invasive species) that are currently shifting coastal regions into novel system states far outside the range of natural variability archived in the fossil record.

Clinoforms with a range of scales are essential elements of prograding continental margins. Different types of clinoforms develop during margin growth, depending on combined changes in relative sea level, sediment supply and oceanographic processes. In studies of continental margin stratigraphy, trajectories of clinoform ‘rollover’ points are often used as proxies for relative sea‐level variation and as predictors of the character of deposits beyond the shelf‐break. The analysis of clinoform dynamics and rollover trajectory often suffers from the low resolution of geophysical data, the small scale of outcrops with respect to the dimensions of clinoform packages and low chronostratigraphic resolution. Here, through high‐resolution seismic reflection data and sediment cores, we show how compound clinoforms were the most common architectural style of margin progradation of the late Pleistocene lowstand in the Adriatic Sea. During compound clinoform development, the shoreline was located landward of the shelf‐break. It comprised a wave‐dominated delta to the west and a barrier and back‐barrier depositional system in the central and eastern area. Storm‐enhanced hyperpycnal flows were responsible for the deposition of a sandy lobe in the river mouth, whereas a heterolithic succession formed elsewhere on the shelf. The storm‐enhanced hyperpycnal flows built an apron of sand on the slope that interrupted an otherwise homogeneous progradational mudbelt. Locally, the late lowstand compound clinoforms have a flat to falling shelf‐break trajectory. However, the main phase of shelf‐break bypass and basin deposition coincides with a younger steeply rising shelf‐break trajectory. We interpret divergence from standard models, linking shelf‐break trajectory to deep‐sea sand deposition, as resulting from a great efficiency of oceanographic processes in reworking sediment in the shelf, and from a high sediment supply. The slope foresets had a large progradational attitude during the late lowstand sea‐level rise, showing that oceanographic processes can inhibit coastal systems to reach the shelf‐edge. In general, our study suggests that where the shoreline does not coincide with the shelf‐break, trajectory analysis can lead to inaccurate reconstruction of the depositional history of a margin.

During a cycle of sea-level variation, coastal environments develop in different position of the continental shelf following seaward and landward shift of the coastline. They vary widely in character, reflecting the wide range of process-regimes that are brought about during the different stages of sea-level variations. Within this scenario, the morphology of continental shelves, mainly resulting from the combined effect of tectonic activity and eustatism, plays an important role in controlling the features and the preservation of coastal environments. Coastal deposits formed along continental shelves in the past, during different stages of sea-level changes, consist of discontinuous and thin depositional bodies, thus their reconstruction can be best carried out through the interpretation of high-resolution seismic data. Such a research approach is adopted in the present study to investigate a portion of the continental shelf of the southernmost sector of SE Sicily, in the offshore of Marzamemi village (Syracuse). The interpretation of high-resolution “Sparker” profiles allowed us to reconstruct the evolution of alluvial and lagoonal environments, established on a substratum of Pliocene or more ancient marine deposits, with the detection of several seismic units and unconformity surfaces, which have been related to alternating sedimentation and erosional processes, depicting the sea-level change framework of glacial-interglacial phases, from the late Pleistocene onward.