The terms late units of the Apulian Basin crop out (South-Apennine foredeep) in the Poggio Imperiale area (Foggia): Stratigraphic characteristics and paleogeographic implications

Abstract

This paper presents the results of a stratigraphical and sedimentological survey which was carried out in a area of the Quaternary Apenninic foredeep (Bradanic Through) where the regressive, final terms of the Apulian Basin crop out. The gathered data allow for the reconstruction of some of the depositional and erosional events that accompanied the sedimentary filling-up of the northern sector of this Basin. A detailed facies analysis enabled us to distinguish two depositional units (Lower Unit: Ul and Upper Unit:US) which are both prograding toward SE. The Upper Unit erosively overlain the Lower one, in which it appears locally entreched. The Lower Unit consists of a Gilbert-type delta system the deposition of which was influenced by wave processes as suggested by facies analysis carried out in its topset and foreset beds. The Upper Unit consists of a coarsening upward sequence due to a transition from offshore-lower shoreface deposition to deltaic accumulation. Upper Unit’s lower part is characterised by facies associations which suggest a progradational nearshore system, influenced by fluvial processes. In particular C1 facies association represents the shelf-lower shoreface transition deposits; it consists of hummocky-cross stratified sandstones and pelitic beds alternating. Low angle cross-stratified sandstones and pebbly sandstones characterise C2 facies association which is representative of lower shoreface. Cd facies association consists of tabular cross stratified, cross stratified and plane bedded sandstones locally alternating with tabular conglomerate beds; such facies association represents upper shoreface deposition influenced by fluvial processes. Tabular, well sorted conglomerate beds made up of mainly disc-shaped clasts characterise C3 facies association (Beachface). The upper part of the same unit consists of facies associations which are consistent with a shelf-type delta system interpretation. DS1 and DS2 facies associations represent mouth-bar deposits which grade basinward into shelfal sandstone lobes (DS3 facies association); prodelta deposits (DS4 facies association) which grade upslope into shelfal sandstone lobes consist of tabular pelitic beds alternating with amalgamated hummocky cross-stratified sandstones. Different stages of the upper unit progradation have been also outlined. The lateral and vertical relationships among the Ul and US facies associations suggest that the two units can be interpreted as system tracts referring to four depositional sequences which reflect the interaction of uplift and glacio-eustatic sea level change occurred during the middle Pleistocene.