Differential compaction as a control on depositional architectures across the Maiella carbonate platform margin (central Apennines, Italy)

Abstract

The role of differential compaction as a control in the creation of accommodation and on compaction-modified depositional features and stratal geometries across the Maiella platform margin, has been investigated through a combined analysis of seismic scale outcrops, porosity evaluation and modeling. Geologic evolution and large exposures make the platform margin of the Maiella an ideal place to investigate the effects of differential compaction. A high-relief cemented carbonate platform, a deep basin filled with highly compactable deposits, and a prograding grain-rich succession sealing morphologic differences across the platform margin, represent suitable features for promoting differential compaction. Stratal relationships across the platform margin exhibit evidence of differential compaction-induced effects, such as basinward divergence and thickening of strata, updip pinch-out of wedge-shaped stratal packages, and an anticline hinge. Porosity analysis and modeling indicate that, through progressive loading, mechanical and chemical processes act in concert to destroy most of the depositional porosity. Mechanical compaction appears to have played the greatest part in the total budget of compaction. However, chemical compaction seems to have played a prominent role in the formation of geometrically consistent depositional profiles during progradation. Due to differential compaction across the platform margin a compaction hinge formed concomitantly with the beginning of progradation, producing a basin-facing monocline characterized by the progressive steepening of basinward stratal dips. The resulting compaction-induced stratal deformation, together with sea level changes, controls the distribution, and depositional timing of wedge-shaped stratal packages during late Cretaceous and Paleocene and the distribution of coral–algal reef buildups, during the late Eocene–early Oligocene. The development of the compaction hinge usually follows the progressive increase of loading, but a decrease in compaction dissipation may be caused by overburdening of compactable deposits. This will cause a delayed compaction-induced subsidence, whose effects will be produced after deposition, i.e. during loading interruption. This mechanism is thought to have an important role in the timing of compaction-induced subsidence throughout the end of Cretaceous and the early Tertiary, and it is considered, together with sea level, as the main controlling process of the occurrence and distribution of downslope sediments, during a long-lasting period of platform emersion.