Stratigraphic organization and predictability of mixed coarse‐grained and fine‐grained successions in an upper slope Pleistocene turbidite system of the Peri‐Adriatic basin

Abstract

The early Pleistocene clastic succession of the Peri‐Adriatic basin, eastern central Italy, records the filling of a series of piggyback sub‐basins that formed in response to the development of the eastward‐verging Apennine fold‐thrust belt. During the Gelasian (2·588 to 1·806 Ma), large volumes of Apennine‐derived sediments were routed to these basins through a number of slope turbidite systems. Using a comprehensive outcrop‐based dataset, the current study documents the depositional processes, stratigraphic organization, foraminiferal age and palaeodepth, and stratigraphic evolution of one of these systems exposed in the surroundings of the Castignano village. Analysis of foraminiferal assemblages consistently indicates Gelasian deposition in upper bathyal water depths. Sediments exposed in the study area can be broken into seven main lithofacies, reflecting specific gravity‐induced depositional elements and slope background deposition: (i) clast‐supported conglomerates (conglomerate channel‐fill); (ii) amalgamated sandstones (late stage sandstone channel‐fill); (iii) medium to thick‐bedded tabular sandstones (frontal splay sandstones); (iv) thin to thick‐bedded channelized sandstones (sandy channel‐fill); (v) medium to very thin‐bedded sandstones and mudstones (levée‐overbank deposits); (vi) pebbly mudstones and chaotic beds (mudstone‐rich mass‐transport deposits); and (vii) massive mudstones (hemipelagic deposits). Individual lithofacies combine vertically and laterally to form decametre‐scale, disconformably bounded, fining‐upward lithofacies successions that, in turn, stack to form slope valley fills bounded by deeply incised erosion surfaces. A hierarchical approach to the physical stratigraphy of the slope system indicates that it has evolved through multiple cycles of waxing then waning flow energy at multiple scales and that its packaging can be described in terms of a six‐fold hierarchy of architectural elements and bounding surfaces. In this scheme, the whole system (sixth‐order element) is comprised of three distinct fifth‐order stratigraphic cycles (valley fills), which define sixth‐order initiation, growth and retreat phases of slope deposition, respectively; they are separated by discrete periods of entrenchment that generated erosional valleys interpreted to record fifth‐order initiation phases. Backfilling of individual valleys progressed through deposition of two vertically stacked lithofacies successions (fourth‐order elements), which record fifth‐order growth and retreat phases. Fourth‐order initiation phases are represented by erosional surfaces bounding lithofacies successions. The component lithofacies (third‐order element) record fourth‐order growth and retreat phases. Map trends of erosional valleys and palaeocurrent indicators converge to indicate that the sea floor bathymetric expression of a developing thrust‐related anticline markedly influenced the downslope transport direction of gravity currents and was sufficient to cause a major diversion of the turbidite system around ...

Multi‐scale analysis of a migrating submarine channel system in a tectonically‐confined basin: The Miocene Gorgoglione Flysch Formation, southern Italy

“…Hubbard et al ., ). In these intra‐channel settings, the thinly interbedded sandstone and mudstone facies are confined within primary channel surfaces and onlap against them (Pringle et al ., ; Kane & Hodgson, ), showing a rapid transition to amalgamated sandstones laterally, towards the channel axes (Deptuck et al ., ; Di Celma et al ., ; Hubbard et al ., ). However, in the GF succession, this type of lateral transition from thin bedded F.A.2 deposits to thick bedded sandstones of F.A.1 has not been observed within the channelforms.…”

Off-shelf sedimentary record of recurring global sea-level changes during the Plio-Pleistocene: evidence from the cyclic fills of exhumed slope systems in central Italy

“…Within the Castignano system at least six successive unconformity-bounded sequences have been recognized (Di Celma et al 2012). The chronostratigraphic frame for these turbidite strata and the surrounding hemipelagic mudstones has been constructed using age-diagnostic benthic and planktonic foraminifera.…”

Evolution of the Gelasian (Pleistocene) slope turbidite systems of southern Marche (Peri-Adriatic basin, central Italy)

“…In this region, a series of erosively confined, sandstone-and conglomerate-filled turbidite systems (namely, Monte Ascensione, Castignano, Offida, and Montedinove systems, Figure 4) developed along the length of the slope and served as point-source conduits through which coarse sediment was transported to the deeper waters of the Peri-Adriatic basin. Microfossil assemblages indicate that sediments were deposited at upper bathyal depths, between 200 and 400 m (Di Celma et al, 2013). Clast composition of the turbidite sediments records extrabasinal input and includes a variety of lithologies (limestone, chert, marl, calcarenite, and sandstone) derived from erosion of Late Jurassic to Miocene formations cropping out in the adjacent central Apennine thrust belt, pointing to major source regions to the west.…”

“…Lying above a major basal incision surface, strata of the Castignano system crop out over an area of approximately 25 km 2 that extends from Montecalvo in the south, where their eroded headward end projects into the air, to the Tesino River in the north, where the turbidite succession disappears into the subsurface (Di Celma et al, 2013). The Castignano turbidite system traverses across the central portion of the study area in a south to north direction and occurs as an elongated sedimentary body that is about 2 -3 km wide, at least 5.5 km long and has a maximum total thickness of 270 m. The overall stratigraphy of the Castignano system comprises a heterogeneous succession of conglomerates, sandstones, thinly bedded sandstone and mudstone heterolithics, and pebbly mudstones, which are organized into a composite upward fining trend.…”

“…Regional field mapping of the exhumed early Pleistocene sedimentary succession of the PeriAdriatic basin (eastern central Italy) led to the identification of a series of deeply incised, mixed mud, and coarse-grained clastic slope turbidite systems (Di Celma, 2011;Di Celma, Cantalamessa, & Didaskalou, 2013;Di Celma, Cantalamessa, Didaskalou, & Lori, 2010;Di Celma, Teloni, & Rustichelli, 2014), which preserve an extraordinary record of orbitally dictated glacio-eustatic changes in the sea level (Cantalamessa et al, 2009;Di Celma & Cantalamessa, 2012). This article deals with four of these turbidite systems exposed at Monte Ascensione, Castignano, Offida, and Montedinove in southern Marche ( Figure 1) and focuses on the exceptional opportunity they provide to document, from an outcrop perspective, the important impact of structurally generated bathymetric relief on the routing of gravity currents depositing sand on deep-water basin floors and the long-term evolution of continental slope morphology from a thrust-related stepped slope, to a smooth, healed slope.…”