Evoluzione geologica del settore settentrionale del Tavoliere di Puglia (Italia meridionale) nel Pleistocene medio e superiore

Abstract

Moretti M. et al., Evoluzione geologica del settore settentrionale del Tavoliere di Puglia (Italia meridionale) nel Pleistocene
medio e superiore. (IT ISSN 0394-3356, 2010).
The Tavoliere di Puglia is the third largest plain in Italy (surface area is about 3.500 Km2 ) and is located between the southern
Appenninic Chain (Subappenino dauno) and the Apulian foreland (Gargano promontory). From a geological point of view, the Tavoliere
di Puglia plain represents the northern sector of the southern Appenninic Plio-Pleistocene foredeep known as Bradanic trough. In the
lower Pleistocene, the area was subjected to a phase of subsidence (with a rate in the order of 1 mm/y), while, from middle Pleistocene
to present-day, a moderate uplift phase occurred.
Data field from the survey for the new Geological Map of Italy (C.A.R.G. Project) and analyses carried out on well logs allowed the
detailed study of the latest phases of sedimentation during the regional uplift of the northern sector of the Bradanic trough. The geological survey was carried out in an area (408 “San Bartolomeo” and 396 “San Severo” Sheets of the new Geological Map of Italy -
1:50.000 scale) that covers the entire Plio-Pleistocene foredeep extending from the external thrust sheets of the Subappennino dauno
to the western Gargano highs. This paper presents only the data collected during the survey of the middle upper Pleistocene deposits:
they are marine, transitional and continental deposits and are clearly terraced at different elevations above present sea level. They lie
on unconformity surfaces above older units represented mainly by Miocene Apenninic units in the western sectors, Plio-Pleistocene
argille subappenine unit in the foredeep area and carbonatic Mesozoic-Cenozoic units in the western Gargano area.
The recognition of unconformity surfaces of great lateral extent allowed us to distinguish 7 different synthems grouped in the Tavoliere di Puglia supersynthem. Some synthems contain a lower marine and/or transitional subsynthem and an upper alluvial subsynthem separated by an unconformity surface. Marine and transitional subsynthems crop out in the eastern part of the study area (close to San Severo and Apricena area) and are represented mainly by coarsening-upward successions deposited in deltaic, proximal marine and low-energy protected embayment settings.
In the western and higher sectors, alluvial subsynthems occur; they contain coarsening-upward successions of (proximal to distal) alluvial fan environments passing eastward to braided and coastal alluvial plain environments. Lateral facies changes can be followed gradually from areas next to the chain toward the eastern foreland areas. Facies changes can be observed also comparing synthems of
different ages: for example, alluvial facies observed at the same distance from the chain are coarser-grained in the older synthems and
finer-grained in the younger ones; the basal unconformity of different alluvial synthems show similar features: it is very inclined to the
East in older synthems and becomes gradually less steep for the younger ones.
Our data show that the Tavoliere di Puglia supersynthem represents a complex assemblage of marine and alluvial terraced deposits
that records the interaction between regional uplift and sea-level changes. We propose a new set of detailed paleogeographic evolutionary stages for the northern sector of the Bradanic trough during middle and upper Pleistocene. In addition, these data allow us to compare the Tavoliere di Puglia plain and southern Bradanic trough evolutions.