Marcello Tropeano

Filling and cannibalization of a foredeep: the Bradanic Trough, Southern Italy

Abstract The Bradanic Trough (southern Italy) is the Pliocene-present-day south Apennines foredeep. It is a foreland basin as subsidence due to westward subduction of the Adria Plate involves the continental crust of the Apulian domain. The infill succession of the Bradanic Trough is characterised by the presence of a long thrust sheet system (the so called ‘allochthon’) that occupied part of the accommodation space created on the foreland by subduction. The upper part of the infilling succession crops out along numerous sections. About 600 m of the 3–4 km basin-fill succession is exposed as the Bradanic Trough has experienced uplift during Quaternary times. Outcropping successions are mainly characterized by shallow-marine deposits comprising carbonates of the Calcarenite di Gravina Formation, silty clay hemipelagites of the Argille subappennine Formation and coarse-grained bodies of the ‘Regressive coastal deposits’. The Calcarenite di Gravina Formation (Middle-Late Pliocene-Early Pleistocene in age) crops out in a backstepping configuration onto the flanks of the Apulian Foreland highs. It displays evidence of strong transgression onto a karstic region previously dissected in a complex horst and graben system. The Argille subappennine Formation (Late Pliocene-Middle Pleistocene in age) succeeds the carbonate sedimentation on the foreland side of the basin and represents the shallowing of the basin in the other sectors of the Bradanic Trough. Toward the Apennines chain, in the wedge-top area of the foredeep, the Argille subappennine Formation covers the allochthon, while in the depocentre (in the foredeep sensu stricto) the same formation overlays turbidite deposits. The latter characterize the deeper part of the successions, and are mainly buried below the allochthon. The Regressive coastal deposits (Early-Late Pleistocene in age) represent the upper part of the succession. They consist of coarse-grained wedges that lie on the hemipelagites of the Argille subappennine Formation in, alternatively, conformable or erosional contact. The wedges of the Regressive coastal deposits stack in a downward-shifting configuration, which indicates deposition during uplift. The Quaternary development of the Bradanic Trough differs from that of the central and northern Appennines foredeep. The latter is characterized by aggradation of shallow-marine and alluvial sediments in a subsiding remnant basin, whose filling records a basin-scale depositional regression. In contrast, the Bradanic Trough is characterized by a basin-scale erosional regression and the last evolutive phase of this sector of the Apennines foredeep is best defined as a cannibalization phase rather than a filling or overfilling phase.

Horizontal to Vertical Spectral Ratio (HVSR) Measurements in the Area Damaged by the 2002 Molise, Italy, Earthquake

Following the 2002 Molise, Italy, earthquake, we performed a set of horizontal to vertical spectral ratio (HVSR) measurements in the damaged area. We recorded microtremors in all the municipalities reaching VI on the Mercalli-Cancani-Sieberg intensity scale. To calibrate our measurements, we installed accelerometers in two of the most damaged areas. We wanted to study HVSR in an area that is geologically different from areas commonly affected by earthquakes in the Southern Apennines. We also wanted to avoid the damage-attraction effect: after a strong event, most researchers study site amplification just where most of the damage has occurred. They might not consider that different structure vulnerability may mask the true distribution of site amplification. We checked for a possible correlation between observed intensity and the average of the non-flat HVSR measured in each municipality. The significant correlation indicates that site amplification has played a role in the damage pattern observed.

Response of Plio-Pleistocene mixed bioclastic-lithoclastic temperate-water carbonate systems to forced regressions: the Calcarenite di Gravina Formation, Puglia, SE Italy

Upper Pliocene-lower Pleistocene shallow-marine temperate-water carbonates of the Calcarenite di Gravina Formation crop out in the Murge area of Puglia, SE Italy, and record a regional subsidence-driven transgression that was punctuated by higher-frequency forced regressions. Sedimentation occurred during the drowning of a complexly faulted island archipelago whose bedrock was exclusively composed of deformed Cretaceous platform carbonates. High-energy temperate-water bioclastic carbonate systems dominated marine environments, but bioclasts were locally mixed with carbonate lithoclasts derived from the Cretaceous limestones bedrock and supplied to the shoreline via ephemeral rivers. This setting allows us to compare the depositional response of bioclastic-dominated and mixed bioclastic-lithoclastic temperate-water carbonate systems to relative sea-level changes, and in particular to forced regressions within a long-term transgressive sequence set. Bioclastic dominated temperate-water carbonate systems are comprised of a nearshore non-depositional abrasion zone and an offshore accumulation zone; long-term subsidence led to erosional transgression through nearshore abrasion and bioerosion of the drowning archipelago. The bioclastic-dominated carbonate system was best developed during relative sea-level rises and highstands, with offshore cyclic subtidal carbonate successions interpreted to record higher-frequency relative sea-level fluctuations. Forced regressions and lowstands were associated with basinward migration of the abrasion zone and development of a subaerial exposure surface that passed basinward into marine rock- and softgrounds on the shelf; little additional sediment was supplied from updip karstic areas of the island archipelago where superficial drainage was limited. In contrast, mixed bioclastic-lithoclastic carbonate systems are characterized by reciprocal sedimentation, developed where ephemeral rivers supplied carbonate lithoclasts to the shoreline. In these systems, bioclastic sedimentation typified relative sea-level rises and highstands whereas forced regressions and lowstands were associated with the development of coarse lithoclastic deposits. Forced regressive-lowstand deposits are represented by narrow progradational gravel beaches in ramp settings whereas small coarse-grained deltas formed against steep fault-bounded coastlines; both lack an aggradational component. Lower surfaces of the forced regressive-lowstand units are sharp and record abrupt basinward facies shifts. However, these basal surfaces were largely inherited, formed in the nearshore abrasion zone of the preceding transgressive-highstand bioclastic-dominated carbonate system. Rockgrounds formed in this way were not substantially modified by marine shoreface erosion during sea-level fall. The upper bounding surfaces of the forced regressive/lowstand deposits are also marine in origin and developed in response to rapid sea-level rise and landward translation of the shoreline. These surfaces were associated with nearshore abrasion and ravinement so that subaerial exposure surfaces were reworked in the marine environment and have very low preservation potential. Accordingly, the forced regression/lowstand sediment bodies are bounded by marine erosion surfaces and enclosed within sediments and/or surfaces formed in offshore environments.

Sedimentology and hydrodynamics of mixed(siliciclastic-bioclastic) shallow-marine deposits of Acerenza (Pliocene, Southern Apennines, Italy)

During the Pliocene, along the Apennines front of Southern Italy (Acerenza area), a sector of the wedge-top basin hosted shallow-marine siliciclastic-carbonate (-bioclastic) sedimentation. Sediments consist of mixed arenites and rudites forming an up to 30 m thick unit. Based on the recognition of textural features, sedimentary structures, and degree of segregation between siliciclastic and bioclastic particles, facies analysis revealed 10 facies grouped into 5 associations. They suggest the occurrence of either wave or current dominated environments, showing different degrees of heterolithic segregation between siliciclastic and bioclastic particles. The depositional system was characterised by a gentle sloping profile irregularly undulated by syndepositional gentle folds. Waves dominated the shallowest areas of the mixed system and the terrigenous fraction derived mainly from wave erosion of substrate (arenaceous) rocks. These areas were located at the top of anticlines at depths corresponding to that of an upper shoreface sector of a classic coastal profile. The bioclastic fraction derived from the fragmentation of an in situ heterozoan skeletal-carbonate factory. Almost constant waves activity prevented segregation of the siliciclastic and bioclastic fractions in the lower shoreface zones. In relatively deeper environment of the mixed system (offshore transition), persistent unidirectional currents dominated, with development of tide-influenced 2D and 3D dunes. Repeated oscillations of the water column in the sheltered coastal areas produced modulation of current velocity favouring segregation of the heterolithic fractions along the dune foresets. Finally, in the deepest sector of the system (offshore), pervasive bioturbation dominated causing unsegregation of the siliciclastic and bioclastic fractions.

Fluvial landforms in relation to the geological setting in the “Murge Basse” karst of Apulia (Bari Metropolitan Area, Southern Italy)

Abstract Please click here to download the map associated with this article. An integrated geological and geomorphological study was performed in order to describe the landform-features of the Bari Metropolitan Area (“Città Metropolitana di Bari”, Apulia, Southern Italy). The study is focused on the coastal sector of the “Murge Basse” area. This latter is characterized by alow-relief carbonate landscape gently dipping toward the Adriatic Sea, and represents the eastern and lowermost part of “Murge”, a karstic region belonging to the South Apennines foreland. Results coming from field survey, aerial-photo interpretation, and digital terrain model analysis were summarized in a 1:50,000 scale map which can contribute to land management and to assessment of flood hazards in a metropolitan area. In fact, although the “Murge” area shows some features typical of karst landscapes, it exhibits a well developed drainage-network, formed by a dense dendritic pattern in the headwater zone (“Murge Alte”) which evolves into regularly spaced, incised valleys cutting through a staircase of marine terraces moving towards the coastal area (“Murge Basse”). Some of these valleys are joined to sub-horizontal areas (corresponding to some marine terraces), and represent relict landforms related to ancient sea-level changes that occurred during middle and late Pleistocene times. These surfaces located downstream of incised valleys may represent sectors of high flooding hazard in the Bari Metropolitan Area.

Stratigraphic organization of rudist biogenic beds in the Upper Cenomanian successions of the Western Murge (Apulia, Southern Italy)

Abstract In the Murge the Upper Cenomanian limestones belonging to the Sannicandro Member of the “Calcaredi Bari” Formation are characterized by four facies associations (A-D), related to a prograding depositional system. The lateral zonation consists of a lagoon (A) passing seaward to sandy shoals with rudist buildups (B), to sandy bioclastic slope (C) and, lastly, to shallow basin (D). The stratigraphic organization consists of lateral and vertical stacking of sigmoidal- and wedge-unit sets controlled by changes in accommodation.

1:5,000 geological map of the upper Cretaceous intraplatform-basin succession in the Gravina di Matera canyon (Apulia Carbonate Platform, Basilicata, southern Italy)

Along the slopes of the Gravina di Matera canyon, below and in front of the Sassi di Matera, i.e., the old Matera town (Basilicata, southern Italy), an about 200 m thick succession of upper Cretaceous carbonates extensively crops out. These carbonates belong to the Apulia Carbonate Platform and, in the official geological map, are referred to the Calcare di Altamura Fm, a lithostratigraphic unit composed of shallow-marine peritidal limestones. In order to study the whole outcropping succession, a geological survey was performed in the area and an unaspected intraplatform shallow-basin suite of limestones has been recognized within the Calcare di Altamura Fm. On the basis of lithologic characters, the whole succession has been divided into informal lithostratigraphic units a-g. The base of the succession (unit a) is represented by a crudely stratified bioclastic floatstone-rudstone locally interested by in situ brecciation, a phenomenon that often is the precursor of deep changes in a carbonate platform. Unit a sharply passes upward to thinly bedded and finely planar-laminated mudstone interested by slumps (unit b), conformably covered by dolostones (unit c). Dolostone gradually passes to cherty limestones (unit d) that in turn pass to wackestones (unit e) covered by a megabreccia (unit f). All these units (a-f) indicate that this area of the Apulia Platform performed a change from classic platform environments to slope- and to basin-ones, before the restarting of typical facies of shallow-marine carbonate platform environments (unit g). This subdivision in units of the outcropping succession led us to informally define a member, the Matera member (ALT1), within the upper Cretaceous Calcare di Altamura Fm (ALT). Most likely, the Matera member (units a-f) represents a shallow-basin developed within the Apulia Platform during Late Cretaceous, most likely related to extensional tectonics. Other examples of slope-to-basin sedimentary suite were previously observed within the upper Cretaceous succession of the Apulia Platform and the occurrence of another shallow-basin in the interior of the same platform opens a new and still understimated regional tectonic- and paleogeographic-scenario. Moreover, it should be highlighted that the geological surveyed area belongs to a Regional Natural Park since the 1990 (Parco Archeologico Storico Naturale delle Chiese Rupestri del Materano also known as Parco della Murgia Materana) and that Matera, besides being in the Unesco Word Heritage list since the 1993, has been voted European Capital of Culture 2019. Therefore, the obtained 1:5,000 geological map, apart from documenting some lithostratigraphic evidences of the intraplatform basin, represents an essential tool for both (i) future studies regarding the upper Cretaceous tectono-stratigraphic evolution of the Apulia Platform, and (ii) a geological base for many visitors interested in the cultural and geological heritage of Matera and its territory.

Note illustrative della carta geologica dell'area urbana di Bari in scala 1:25.000

Notes to the geological map of the urban area of Bari (southern Italy) 1:25.000 scale.This paper shows the results coming from the detailed geological mapping performed on the urban area of the city of Bari (Puglia region, southern Italy). It is a large area (about 50 km2), with many inhabited places, and intensely urbanized. For this reason a geological map that could provide an up-to-date and useful tool for professional geologists daily working on the region, was realized.The area represented in the geologic map of the urban area of the city of Bari, at the scale 1:25.000, lies on the eastern Murge, which represents the central part of the Apulian foreland, the south-Apennines foreland. In the Murge area, the foreland is characterized by a thick Mesozoic sedimentary succession overlain by relatively thin and discontinuous Quaternary deposits. Locally, the exposed Mesozoic succession is about 150 m thick, and is represented by a part of the Calcare di Bari Fm, made up of biopeloidal and peloidal wackestones/packstones alternated with stromatolitic bindstones with frequent intercalations of dolomitic limestones and grey dolostones. Depositional environments are related to a low-energy inner-platform depositional system and biostratigraphic data allowed us to refer the age of the succession cropping out in the city of Bari to the Late Albian-Early Cenomanian.The lower Pleistocene Calcarenite di Gravina Fm unconformably lies on the Calcare di Bari Fm. The lower boundary is transgressive and is locally marked by reddish residual deposits (terra rossa) and/or by brackish silty deposits passing upward to shallow-water calcarenites rich in bioclasts. Basically this formation is made up of litho-bioclastic calcarenites and calcirudites with packstone/grainstone texture, rich in mollusks, red algae, serpulids, echinoids and benthic foraminifers. The thickness of this unit ranges from few metres up to 20 m, and its depositional environments are related to alluvial or offshore systems. The age is early Pleistocene (Gelasian?-Calabrian). Regionally, the Calcarenite di Gravina Fm represents the record of the lower Pleistocene subsidence of the Apulia foreland.The Murge supersynthem groups all the marine terraced deposits unconformably lying on all older units and consists of a heterogeneous assemblage of mixed silicoclastic and carbonate sediments formed in shallow-marine and transitional environments. The thickness of the three synthems forming the supersynthem is usually few metres thick and the age ranges from middle to late Pleistocene. These synthems record a phase of regional uplift which started at least from middle Pleistocene; this uplift, in combination with the Pleistocene glacioeustatic oscillations, produced several relative sea-level changes which caused the distribution of these synthems to different altitudes above sea level.The lame delle Murge supersynthem groups all the terraced alluvial deposits cropping out in the studied area. These deposits unconformably lie on the previous units and are placed at different heights inside little canyons, characterizing the area and locally named lame. These deposits consist of either well cemented or poorly cemented carbonate conglomerates with a reddish silty-sandy matrix. The thickness of these deposits ranges from few metres up to 10 m and the age is middle Pleistocene-late Pleistocene.The picture is completed by upper Pleistocene-Holocene actual and present-day alluvial deposits, made up of carbonate gravels with reddish fine-grained matrix.

Texture and composition of the Rosa Marina beach sands (Adriatic coast, southern Italy): a sedimentological/ecological approach

Abstract Beach sands from the Rosa Marina locality (Adriatic coast, southern Italy) were analysed mainly microscopically in order to trace the source areas of their lithoclastic and bioclastic components. The main cropping out sedimentary units were also studied with the objective to identify the potential source areas of lithoclasts. This allowed to establish how the various rock units contribute to the formation of beach sands. The analysis of the bioclastic components allows to estimate the actual role of organisms regarding the supply of this material to the beach. Identification of taxa that are present in the beach sands as shell fragments or other remains was carried out at the genus or family level. Ecological investigation of the same beach and the recognition of sub-environments (mainly distinguished on the basis of the nature of the substrate and of the water depth) was the key topic that allowed to establish the actual source areas of bioclasts in the Rosa Marina beach sands. The sedimentological analysis (including a physical study of the beach and the calculation of some statistical parameters concerning the grain-size curves) shows that the Rosa Marina beach is nowadays subject to erosion.

Stratigraphy of the subsurface of the Metaponto Plain vs a geophysical 3D view of the late Pleistocene incised-valleys (Basilicata, Southern Italy)

The stratigraphical analysis of several boreholes drilled in the Metaponto coastal plain (Basilicata region, southern Italy) highlighted the occurrence of two irregular erosional surfaces bounding three main overlapping sedimentary units. The upper unit, which base has been detected by using a geophysical method for the H/V spectral ratio (HVSR) of microtremors, fills and covers some paleovalleys that were incised during the Last Glacial Maximum (LGM). A 3D view of a main geophysical unconformity shows a surface with the occurrence of some deeper, narrow, and sinuous zones running roughly perpendicular to the present-day coastline and at depths of up to 90 m below the present-day sea level. These narrows likely correspond to the paleovalleys that developed in the region during the LGM and are buried below the Metaponto coastal plain. Some discrepancies between the geophysical and the geological data may be explained either as induced by a not well constrained projections of boreholes (from which derive the lithostratigraphic interpretations) or considering that the sedimentary models of incised-valley fills suggest the presence of different coeval deposits along dip through paleovalleys, inducing a contrast of seismic impedance readable as paleotopography rises.