L'entroterra di Barletta (Bari): considerazioni sui rapporti fra stratigrafia e morfologia

Abstract

The Barletta hinterland is formed by terrigenous and carbonatic sediments typical of zones of transition between different units; this makes the area suitable for geomorphological studies integrated with boreholes data. The first part of the study consists of various phases including large scale geological and morphological field surveys of the entire area, the study of 18 borehole logs, collection and filing of data from geognostic wells and wells drilled by both public and private organizations for various purposes. Core samples were analysed to characterise their lithological, mineralogical and paleontologicai content. The resulting data provide useful information on the sedimentation environment of lithostratigraphic units and the paleoenvironmental evolution. It has also been possible to distinguish successions of several sedimentary cycles. Lateral variations and mutual geometric relationships of sedimentary bodies were reconstructed by correlating field data with core data. The morphological features of each Quaternary sedimentary event have been identified and the relationships between sedimentation and tectonic activity are outlined. Data concerning the Mesozoic substratum, the "Calcarenite di Gravina" (Gravina Calcarenite) and "Argille subappenniniche" (Subapenninic Clay) Formations, and recent terraced deposits were digitised and mapped. Buried forms have been interpreted and mapped, in spite of what is commonly thought, the structural setting of the studied area is markedly controlled by tectonics, as shown by buried and superficial landforms. Two tectonic alignments have been identified: The main one has a NW-SE trend (Apenninic direction) and runs parallel to the coast. The second alignment has NE-SW antiapenninic direction, and is subparallel to the terminal stretch of the Ofanto River. In particular, both the Mesozoic substratum and, less markedly, the Quaternary deposits have a conformable step structure dipping towards the Adriatic Sea and the Ofanto River valley line. This tectonic style is complicated by the presence of structural highs and lows. In addition to the sediments deposited by the entering sea during the "Bradanic graben" Cycle, three more superimposed sedimentary marine to lagunar cycles have been recognized. The first and the third of these cycles are characterized by silico-clastic deposits; the second cycle consists of predominant carbonatic sediments. The geomorphological study of surfaces has yielded indications on the sequence of sea level changes, in particular on sea level highstands not marked by sedimentary evidence.