The geological map of the Sheet 396 “San Severo”, here presented at the scale 1: 50.000, was investigated and surveyed using offi cial topographic maps at the scale 1: 25.000. The fi eld work benefi ts also of unpublished stratigraphic and tectonic data belonging to a doctoral thesis in sedimentary geology (Spalluto, 2004). The investigated area lies in the northern part of the Puglia region (southeastern Italy) and belongs to two main geographic and geologic domains: a) the Apulian Foreland (western sector of the Gargano Promontory) and the Bradanic Foredeep (northern sector of the Tavoliere delle Puglie). The two sectors represent respectively the foreland and the foredeep areas of the Southern Apennines chain.
Stratigraphic data collected during the survey of the Foglio San Severo produced a strong revision of the lithostratigraphy of the area respect the previous edition of the Geologic Map of Italy (scale 1:100.000) for both Meso-Cenozoic and Quaternary units. The resulting new lithostratigraphic framework allowed to
fournish new stratigraphic constraints for the geologic evolution of the area. Moreover, this framework reduces the proliferation of lithostratigraphic nomenclatures existing in literature proponing the adoption of a nomenclature valid at a regional scale. The western sector of the Gargano Promontory (eastern and northern part of the Sheet San Severo) is mostly made up of Mesozoic and Cenozoic carbonate
units formed in shallow-water environments. The oldest outcropping unit is the Calcare di Bari Fm. (Callovian p.p.-Aptian p.p.), which is about 900 m thick and form the bulk of the whole Mesozoic succession. It consists of a fairly monotonous and conformable succession of peritidal and shallow subtidal limestones formed in a broad inner-platform setting. The stacking of lithofacies and lithofacies association
in the succession allowed to recognize the following three informal members:
a) Monte Calvo mb. (Callovian p.p.-Valanginian p.p.), about 300-350 m thick; b) Borgo Celano mb. (Valanginian p.p.-Aptian p.p.), about 500-600 m thick; c) Ostreids and Requienids member (Aptian p.p.), about 80 m thick. The three members show almost constant lithofacies assemblages consisting mainly of mud-supported mudstone-wackestone formed in restricted lagoonal environments. Locally these
lithofacies are cyclically alternated to cryptmicrobial limestones and residual clay layers indicating deposition in tidal fl at environments with periods of pedogenesis due to subaerial exposure. The boundaries between members are usually sharp and are marked by the temporary disappereance of tidal fl at lithofacies outpaced by relatively deeper lagoonal ones. In each member, the rapid deepening is followed
by a gradual shallowing marked by the gradual restoration of tidal flat conditions becoming more and more widespread towards the top of each member. The calcare di Altamura fm. (Coniacian p.p.-Santonian p.p.) crops out in few areas in the southern and western part of the Sheet San Severo. It unconformably lies on a few metre thick bauxites (Turonian in age) indicating a phase of prolonged emersion of the Apulian Platform. The Calcari di Monte Acuto Fm. (Santonian p.p.) crops out in the western part of the Foglio San Severo and it is 50-60 m thick. It conformably lies on the calcare di Altamura fm. and it unconformably lies below the Tavoliere delle Puglie supersynthem. It is composed of: i) blocks of rudist limestones coming
from the calcare di Altamura fm.; ii) laminated packstone/grainstone with rudist fragments; iii) wackestone/packstone with radiolarians, planctonic foraminifers and calcispheres with intercalation of chert nodules and layers. Lithofacies suggest deposition in a slope environment.
The basalti Picritici di Mass. S.Giovanni in Pane Fm. (Paleogene ?) crops out in the northwestern part of the Sheet “San Severo”. This unit consists of blocks of pycritic basalts probably deriving from the erosion of basaltic dykes intruded in the lower Cretaceous limestones of the Calcare di Bari Fm.
Neogene units crop out in few areas at the margin of the Gargano Promontory. These units are composed of similar facies features and are formed in neritic carbonate environments. The informal Masseria di Belvedere fm. (middlelate Serravallian) is about 10-15 m thick and unconformably lies on Mesozoic
limestones. Terra rossa layers locally mark this boundary. This unit mainly consists of: i) grainstone/packstone with benthic foraminifers, serpulids, mollusks, echinoids, red algae and bryozoans fragments; ii) fl oatstone/bafflestone with corals, barnacles, bivalves and echinoids in a matrix of wackestone with planctonic foraminifers and sponge spicules. The informal Masseria Spagnoli fm.
(late Tortonian) is about 10 m thick and lies with a marked angular unconformity on Mesozoic limestones and on the Masseria Belvedere fm. It is locally covered by the cemented alluvial fans of the Gargano Promontory. This unit mainly consists of packstone/grainstone with benthic foraminifers, serpulids, mollusks, echinoids, bryozoans and rare planctonic foraminifers with intercalations of oyster and
pectinid-rich lags. The informal Masseria di Vituro fm. (late Messinian ?) is about 20-25 m thick and unconformably lies on Mesozoic limestones and it underlies the cemented alluvial fans of the Gargano Promontory. From bottom to top this unit is made up of grain-supported and coarse calcareous conglomerates fining up in microconglomerates in a grainstone matrix with benthic foraminifers and
serpulids. The upper part of the unit consists of laminated grainstone with benthic foraminifers, mollusks and red algae. The Calcarenite di Gravina Fm. (middle-upper Pliocene) is about 30-40 m thick
and unconformably lies on Mesozoic limestones and on Masseria Belvedere fm and underlies the Quaternary deposits of the Tavoliere delle Puglie supersynthem. This unit shows a fi ning-up/deepening-up trend marked by the gradual transition from coarse rudstones with mollusks, echinoids, and serpulids in a bioclastic packstone/grainstone to packstone/grainstone rich in planctonic and more rarely benthic foraminifers and with mollusks, echinoids and red algae fragments. The argille subappennine fm. (upper Pliocene - lower Pleistocene) crops out only in a very localised zone in the south-western sector of the sheet. It is composed of alternating beds of silty shales and fi ne- to medium-grained sandstones. More
data come from literature and wells carried out to describe the overlying units of the Tavoliere delle Puglie supersynthem. The argille subappennine fm. represents the substrate of many middle-upper Pleistocene units and reaches a maximum thickness of about 1.000 m in the south-eastern sector of the Sheet “San Severo”. The thickness is mainly conditioned by the structural framework of the underlying
meso-cenozoic units. The outcropping part of this formation is represented mainly by siliciclastic shallow water deposits sedimented below the base of the wave action. The middle to upper Pleistocene deposits have been grouped in the Tavoliere delle Puglie supersynthem. It is composed of 6 different terraced synthems which crops at different Altitudeson the sea level. From the older to the younger we
distinguished the following sinthems: Cava Petrilli synthem (TVP - middle Pleistocene);
Vigna Bocola synthem (TPB - middle Pleistocene); Masseria la Motticella synthem (MLM - middle to upper? Pleistocene); Foggia synthem (TGF - upper Pleistocene); Masseria del Lupo synthem (TLP - upper Pleistocene superiore); Masseria Finamondo synthem (TPF - upper Pleistocene).
Three the older synthems (TVP, TPB and MLM) were divided in 2 subsynthems that are separated by an unconformity of erosive origin (continental deposits on shallowing-upward marine deposits). The younger synthems (TGF, TLP and TPF) are represented mainly by continental deposits. The oldest synthem (TVP) is well exposed in the north-westwern part of the Sheet “San Severo”. The other synthems have been described carrying out some wells. In the studied area, the Tavoliere delle Puglie supersynthem is represented by a terraced marine and alluvial succession which developed in response to a moderate
and constant uplifting and sea-level changes. Alluvial and colluvial Quaternary deposits (late Pleistocene-Holocene), not recognized as belonging to a specifi c basin, crop out along the cliffs that bound
the western and the southern side of the Gargano Promontory (alluvial fans and slope detrital deposits) and in the main karstic valleys and sinkholes and consist of coarse and mostly disorganized calcareous conglomerates or breccias in a residual terra rossa matrix. Terraced deposits are typically cemented.
Quaternary deposits fi ll also the most important karstic caves. “Cave of the Paglicci site” is partly fi lled by late Pleistocene continental deposits, in which two important tombs of Homo sapiens and many rests of vertebrates were found. These important fi ndings and the discover of parietal paintings, make this cave the
most important paleolithic site in Italy. The tectonic features of the Sheet “San Severo” indicate that this area underwent many tectonic phases starting since the Cretaceous till the Quaternary. The foreland area (western Gargano Promontory) is mainly made up of Mesozoic carbonate units showing a monoclinal arrangement with bedding plunging mainly towards SW. The main structural features are represented by
faults and folds, which locally determine several variations in the regional setting of beds. Especially, main faults (Mattinata, Rignano and Candelaro Faults) break up the monoclinal in several blocks showing a different kinematic evolution. These faults generate sub-vertical shear zones, locally with cataclasis showing
mainly strike-slip cinematic indicators. The main structures represent also the most relevant morphologic elements of the foreland area controlling the formation of the hydrography and forming the main cliffs which physically separate the foreland from the foredeep.
The fi rst important element in the recostruction of the tectonic evolution of the area is the recognition of the sharp superposition of slope deposits of the Calcari di Monte Acuto Fm above the shallow-water limestones of the calcare di Altamura fm. This suggests that the western sector of the Gargano Promontory underwented during the Santonian a rapid drowning probably due to the formation of an intraplatform basin.
The most part of the structures mapped in the studied area are polyphasics and formed during the Apennines and Dinarides orogenesis. Published data indicate that the Mattinata Fault shows a left-lateral strike-slip movement and that the most part of structures are kinematically related to the fi eld stress produced by this fault. Stratigraphic constraints confi rm this interpretation, since the older part of
the Calcare di Bari Fm. crops out in the northern sector of the Mattinata Fault and in the southwestern sector of the Rignano Fault. This suggests that the fi eld stress acting on the area, congruent with the E-W left-lateral strike-slip deformation of the Mattinata Fault, contestually produced transpression along NW-SE oriented faults (e.g. Rignano Fault and Monte Granata Fault) and transtension along NESW oriented structures (e.g. S. Egidio pull-apart basin). Intramiocene angular unconformity between Masseria Spagnoli fm. and Masseria Belvedere fm. and the overthrusting of Jurassic limestones of the Monte Calvo member above middle/late Pliocene deposits of the Calcarenite di Gravina Fm. suggest that during Neogene
times several tectonic phases showing similar deformation features occurred.
According to the regional data, during the Plio-Pleistocene, this area (and the entire Apulian foreland) was subject to two different tectonic phases: the first one (Pliocene to lower Pleistocene in age) was related with the active subduction of the Apulian foreland beneath the southern Apenninic Chain; during this phase,
the Apulian foreland recorded an high subsidence rate (about 2 mm/yr); from the Sicilian to present-day, the entire Apulian foreland was subject to a moderate uplift (less than 0,5 mm/yr). We have found many evidences of Neotectonics. In the Apricena area (Masseria Zingari locality), some extensional features have been observed: they are represented by narrow grabens (few tens of meters in lenght) which cut the Masseria Belvedere fm. (early Miocene in age) and are trasferred to the overlying Calcarenite di Gravina Formation (late Pliocene in age). The synsedimentary activity of these grabens is documented by the presence of narrow folds and by the variations in thickness of the Calcarenite di Gravina Formation.
The maximum displacement is always less than 5 m and it decreases upwards. Along the cuts of the older and inactive railway in the same area, a complex distensive fault in the Calcarenite di Gravina Formation (and in its Miocene substrate) occurs: folds and growth structures involve the overlying calcarenites
along the primary and secondary fault planes. Last evidence of the subsidence phase is given by large-scale neptunian dykes (up to 5 m in height): they are restricted at the contact between the masseria Belvedere Fm. and the overlying Calcarenite di Gravina Formation and are represented by large conical fractures in the Miocene substratum which are fi lled by the overlying Pliocene calcarenites;
that is a record of synsedimentary extensional tectonic activity since the overlying unit suffers soft-sediment deformation and many decimetric beds are downward collapsed and/or irregularly folded during the extensional brittle deformation of the substratum.
The middle- to upper-Pleistocene uplift of this area is chiefly documented by the presence of marine and continental terraced deposits that crop out from 140 m a.s.l. to 20 m a. s. l. The documentation of faults associated with this uplift phase often very diffi cult because there are not extensive and continuous outcrops of the middle-upper Pleistocene units. Nevertheless, in a quarry located to the NW of Apricena we founded an extensional fault that cuts the entire thickness of the Colle degli Ulivi subsynthem The fault is subvertical, it is E-W oriented and the maximum vertical displacement is up to 20 m in height. Similar tectonic features
have been reported in the younger San Severo subsynthem.