Luca Capraro

Interplay between tectonics and glacio-eustasy: Pleistocene succession of the Crotone basin, Calabria (southern Italy)

On a global scale, the Crotone basin preserves one of the best-developed and most complete Pleistocene marine records available in outcrop, as important as those in California, New Zealand, and Japan. A deformed, markedly cyclothemic, lower to middle Pleistocene succession is present in the territory of San Mauro Marchesato (Crotone area, southern Italy), showing an overall shallowing trend from slope mudstones to marginal marine and continental deposits. Preservation and high resolution of cyclothems occurred through the interaction between high-amplitude relative sea-level fluctuations, a particular pattern of differential subsidence due to intrabasinal tectonics, and high rates of sediment supply. The studied succession was laid down in the Crotone basin under an extensional tectonic regime, following a major, middle Pliocene contractional phase probably of transpressional nature. Two major unconformities, locally accompanied by angular discordances, occur within the succession. The former, centered at ca. 1.2 Ma, is thought to reflect the opening of the San Mauro subbasin within the Crotone basin in the early Pleistocene, following dextral transtensional motion along north- to north-northeast–trending faults. The latter, with a hiatus lasting from ca. 0.65 to 0.45 Ma, may reflect the decoupling of the Calabrian block with respect to Adria and Sicily, allowing further advancing of the Calabrian arc in the Ionian area, where subduction could continue until the present time. The lower part of the succession (the H. sellii and “large Gephyrocapsa ” Zones, from ca. 1.67 to ca. 1.23 Ma) consists of slope to outer-shelf monotonous mudstones and is bounded at the top by the first unconformity, whose gap suppresses the upper part of to locally the entire “large Gephyrocapsa ” Zone (1.608–1.235 Ma) and the lower part of the “small Gephyrocapsa ” Zone (1.235–0.96 Ma). A number of cyclothems developed in an outer- to inner-shelf environment within the “small Gephyrocapsa ” Zone. Biomagnetostratigraphic constraints strongly support a correlation between the condensed sections of cyclo thems and MIS (marine isotope stage) 33 to MIS 25. From the base of the P. lacunosa Zone (at ca. 0.96 Ma) upward, the succession rapidly becomes sand dominated, a change that can be confidently correlated with the major climatic shift associated with MIS 24 to MIS 22. In the following succession, two tephra layers, named “Pitagora ash” and “Parmenide ash,” provide mappable isochronous surfaces across the subbasin. The sedimentary record is remarkably cyclo themic, characterized by a stack of simple or composite, seaward-prograding, sand- dominated tongues and intervening aggradational deposits related to transgressive-deepening episodes. The cyclothems can be confidently correlated with the oxygen isotope record up to the Matuyama-Brunhes inversion, i.e., up to MIS 19, whereas the stratigraphic record postdating MIS 19 has poorer chronological constraints. Dating is provided by tracing the Parmenide ash in the deeper-water coeval succession of the southern part of the Crotone basin, where the deposits including the ash can be correlated by means of nannofossil biostratigraphy with termination V (transition from MIS 12 to MIS 11). The second unconformity marks an abrupt increase in the proximal character of the sedimentary deposits forming the cyclothems, which incorporate increasing amounts of marginal-marine to continental deposits in the upper part of the subbasin infill. Several lines of direct and indirect evidence indicate that, in spite of the dramatic role of tectonics in shaping stratigraphic architecture, the roles of tectonics and eustasy can be disentangled, owing to the different time scales of the tectonic events and the high-frequency, high-amplitude glacio- eustatic Pleistocene cycles. Interaction between intrabasinal tectonics and high rates of sediment supply allowed forced regressive and possibly also lowstand systems tracts to be preserved in some cyclothems, particularly in the lower part of the succession, an unusual fact in shelf deposits. Considering the far younger age of marine terraces on the Ionian side of Calabria when compared to the Tyrrhenian side, it is thought that, during ongoing subduction of the Ionian crust, a wave of uplift and related extensional tectonics migrated southeastward in the rear of the frontal accretionary wedge.

The environment of Venice area in the past two million years

A ca. 950 m thick succession that was continuously cored in 1971 in Venice has been revisited, in order to reconstruct the environmental history of the Venice area since about 2.15 Ma. Magnetic polarity stratigraphy, integrated with refined calcareous nannofossil biostratigraphy, provides a firm chronostratigraphic framing of the succession. In order to improve the chronological resolution, we derived astrochronological refinements in the lower Pleistocene sapropel-bearing interval by a comparison with other time-correlative sections in the Mediterranean. The pollen record is used as a proxy of climatic changes and as an indirect tool in the chronological reconstruction in the upper part of the succession. The following history has been inferred: (1) in the late Gelasian (late Pliocene), the depositional area was a strongly subsiding shelf which shoaled to near sea level; (2) following a hiatus of a minimum duration of 0.2 Myr, encompassing most of the Olduvai Subchron, the shelf rapidly drowned to bathyal depths over the early Pleistocene (biozones MNN 19a to 19e: from 1.947 Ma to 0.96 Ma). This interval was characterized by starved sedimentation (less than 10 cm/kyr), represented by hemipelagic muds interbedded with sapropel layers; (3) during most of biozone MNN19f (Pseudoemiliania lacunosa Zone, 0.96–0.42 Ma) a thick package of turbidites was laid down as a result of massive terrigenous input from the eastern Southern Alps; (4) later, in the middle part of Chron 1n (Brunhes), deltaic sedimentation, primarily related to the progradation of the paleo-Po system, led to the progressive infill of the basin. This progradational episode was a major building phase, and ended with the first appearance of continental sediments, tentatively correlated with marine oxygen isotope substage 8.4; (5) the upper part of the succession shows a cyclic organization, with an upward increasing amount of marginal-marine and subaerial deposits. In this interval the Venice area was below sea level during glacioeustatic highstands but became emergent during subsequent major glacioeustatic lowstands. Pollen data support an overall good correspondence of continental sediment packages of sequences with glacial conditions and of maximum flooding intervals with interglacial conditions.

Climatic patterns revealed by pollen and oxygen isotope records across the Matuyama-Brunhes Boundary in the central Mediterranean (southern Italy)

Abstract A c. 50 m thick section located in the Crotone Basin (southern Italy) was investigated using oxygen isotopes, pollen and planktonic foraminifera. The section records two complete transgressive-regressive cycles mainly driven by glacio-eustasy. Biostratigraphy and oxygen isotope chronology indicate that the section spans from Marine Isotope Stage (MIS) 22 (c. 0.87 Ma) to MIS 18.3 (c. 0.73 Ma), thus straddling the Matuyama-Brunhes (M-B) boundary which occurs in the middle of MIS 19. The rich pollen assemblages provide a unique record of the vegetation in the central Mediterranean during the Early-Middle Pleistocene climatic transition. Interglacials are characterized by a mesothermic vegetation similar to the present day, whereas a rain-demanding conifer forest dominates the glacials of MIS 20 and MIS 18. This is unexpected because it is generally considered that during the Pleistocene, glacials in central Mediterranean were characterized by steppe (arid) conditions. By contrast, arid conditions occur during the deglaciations. These results are inconsistent with the widespread practice of linking glacials with arid conditions in the central Mediterranean during Pliocene and Early Pleistocene times. This study emphasizes the need to establish more accurate land-sea correlation.

A revision of the stratigraphy and geology of the south-western part of the Crotone Basin (South Italy)

The Crotone Basin, located on a stack of nappes piled up during the late Paleogene-Neogene, formed in the late Neogene to Quaternary as a forearc basin of the Ionian arc-trench system. The process of slab rollback caused rapid trench migration, resulting in an extensionaltranstensional regime persisting most of the time in the forearc area.The late Neogene tectonic evolution was strongly influenced by a NW-directed fault system, interpreted as basement wrench faults leading to partitioning of the basin into separate sub-basins subject to differential subsidence and mutual displacements. Major sequences identified in the area are regarded as tectono-stratigraphic sequences (TSS). The first of them was laid down in the late Serravallian (?) - Tortonian - early Messinian, during the basin opening stage and is bounded at the top by an erosional unconformity, which may be correlated with the well-known intra-Messinian event of the Mediterranean Salinity Crisis. The second TSS, of middle to late Messinian age, is characterized by strongly syntectonic deposits mostly derived from cannibalization of the lower Messiniansuccession, first infilling extensional troughs, then involved in an episode of sinistral transpression along the NW-trending fault system, which generated local overthrusts, sealed by a late Messinian erosional unconformity. The Messinian tectonics probably reflects the interplay between the processes linked to the kinematics of the Calabria block and those triggered by the Salinity Crisis. The erosional unconformity is overlain by widespread coarse fluvial conglomerates, which are the first onlapping term of the third TSS, represented by uppermost Messinian to lower Zanclean deposits, laid down in an extensional-transtensional regime. This TSS was closed by an important late Zanclean episode of dextral transpression along the NW-trending fault system, leading to inversion of the formerbasins, and limited SW-verging thrusts on fault-restraining bends.The unconformity sealing the structures has a clear expression in the northern, marginal part of the Crotone Basin and correlates downbasin with a conformable surface. The fourth TSS is characterized by a long-lasting phase dominated by extension-transtension, leading to high subsidence rate during the latest Zanclean to Early Pleistocene, and accommodating a thick succession of slope mudstones including clusters of diatomaceous bands mostly in the D. tamalis and D. brouweri Zones. In the northern part of the Crotone Basin two phases of drowning separated by an uplift pulse at ca. 2.55 Ma can be recognized, the second of which was a dramatic collapse, between 2.3 and 2.1 Ma. The fifth TSS is bounded at the base by an unconformity at the transition between «large» and «small» GephyrocapsaZones, i.e. at around 1.1-1.2 Ma, correlating basinwards with a conformable surface. The unconformity is erosional and locally angular in the marginal part of the basin, where it seals structures generated by a contractional event documented also elsewhere in the Calabria block. This event, which is accompanied by a strikeslip component, is inferred to be coeval to the Lower Pleistocene important transpressional episode along the Pollino shear system,which led to release of the Calabria block from the southern Apennines.The fifth TSS is characterized by resumed dextral transtension in the Middle Pleistocene along right-stepping NW-trending faults. This episode generated minor pull-apart sub-basins, showing spectacular growth structures in their infilling successions, which developed with shoaling trend up to inferred Marine Isotope Stages 9-8. The onset of shoaling trend was diachronous, being remarkably younger in the southern sub-basin. In the late Middle Pleistocene to Recent times extensional tectonics was dominating, accompanied by local gravity gliding towards the Ionian Sea, arguably triggered by increase in topographic gradient following hinterland uplift, and implying the activation of a linked, thin-skinned extensional and contractional NE- to NNE-directed fault system, with detachment surface possibly soling into Messinian evaporitic-mudstone deposits. It is concluded that the geologic evolution of the investigated forearc area was characterized by an alternation of long-lived stages of extension-transtension expressed by prolonged subsidence preceded by uplift pulses, and short-lived episodes of contraction-transpression.Major drowning episodes in the forearc area are thought to be coeval to the main phases of spreading in the Tyrrhenian basin.

Chronology of the Middle-Upper Pliocene succession in the Strongoli area: constraints on the geological evolution of the Crotone Basin (Southern Italy)

Abstract The aim of this study is to reconstruct the evolution of the Strongoli area, a critical sector of the Crotone Basin (Calabria, Southern Italy), where a thick Middle-Upper Pliocene marine succession is present. The Strongoli succession shows prominent changes in the sedimentary environment that are partly forced by tectonics. Major tectonostratigraphic events have been recognized that might correlate with spreading pulses in the back-arc Tyrrhenian Sea. In particular, we demonstrate that a dramatic basinal collapse at c. 2.3 Ma correlates with the so-called ‘Calabrian transgression’ Auctorum and is close in age to the oceanization of the Marsili Basin.

Early-Middle Pleistocene benthic turnover and oxygen isotope stratigraphy from the Central Mediterranean (Valle di Manche, Crotone Basin, Italy): Data and trends

Ostracod faunal turnover and oxygen isotope data (foraminifera) along the Valle di Manche (VdM) section are herein compiled. Specifically, the material reported in this work includes quantitative palaeoecological data and patterns of ostracod fauna framed within a high-resolution oxygen isotope stratigraphy (δ18O) from Uvigerina peregrina. In addition, the multivariate ostracod faunal stratigraphic trend (nMDS axis-1 sample score) is calibrated using bathymetric distributions of extant molluscs sampled from the same stratigraphic intervals along the VdM section. Data and analyses support the research article “Dynamics of benthic marine communities across the Early-Middle Pleistocene boundary in the Mediterranean region (Valle di Manche, Southern Italy): biotic and stratigraphic implications” Rossi et al. [1].

The Valle di Manche Section (Calabria, Southern Italy): A Candidate Section for the GSSP of the Ionian Stage (Middle Pleistocene Subseries)

We present the key features of the Valle di Manche section (Calabria, southern Italy) and discuss the pros and cons of this stratigraphic succession as a candidate section for the GSSP of the Ionian Stage (Middle Pleistocene Subseries).

Calcareous Nannofossil and Planktonic Foraminifera Biostratigraphy of selected Piacenzian-Gelasian Laminites from Southern Italy

Here we present the biostratigraphic and chronostratigraphic framework of a number of selected diatomaceous laminated intervals from the Crotone Basin (Calabria, Southern Italy). These layers, which we consider correlative to the Eastern Mediterranean Sapropel Layers, range in age from the early Piacenzian to the Gelasian, and show surprising thicknesses, suggesting that they were probably laid down in a landlocked, overfed basin. Specifically, a thick laminite from the surroundings of Cropani (Catanzaro) can be ascribed to nannofossil biozone MNN 16a and planktonic foraminifera biozone MPL 4b (lower Piacenzian) according to the Mediterranean calcareous plankton biostratigraphic zonations. Two laminites from the “Muto” Section (Botricello-Cutro road, Crotone), belong to MPL 5a and MNN 16b/17 Zones (upper Piacenzian). A very thick laminite from the “Timpone dell’Inferno” badland area (near Termine Grosso, Catanzaro), belong to MPL 5b and MNN 18 Zones (middle-upper Gelasian). These biostratigraphic constraints provide a first contribution to a comprehensive paleoenvironmental reconstruction.