Dynamics of benthic marine communities across the Early-Middle Pleistocene boundary in the Mediterranean region (Valle di Manche, Southern Italy): Biotic and stratigraphic implications

Abstract

The Valle di Manche (VdM) section (Calabria, Southern Italy) offers the opportunity to investigate the ostracod turnover along a continuous shelf succession straddling the Early-Middle Pleistocene boundary, and compare it against other paleoenvironmental (i.e., mollusks) and paleoclimatic (Uvigerina peregrina δ 18 O) records. Highresolution (ca. 1 sample/m) ostracod fauna quantitative data, coupled with gradient analysis (Detrended Correspondence Analysis and non-Metric Multi-Dimensional Scaling), document a strong relationship between changes in faunal composition and lithofacies vertical stacking patterns. The comparison between the molluskand ostracod-derived ordination data demonstrates that the meio-and macro-faunal turnover is guided by a common complex gradient: bathymetry. The integrated ostracod-mollusk gradient analysis also provides a trend in water depths along the section, highlighting to what extent such multivariate approach can improve the paleoenvironmental and sequence stratigraphic interpretation of ancient shallow marine successions. When plotted stratigraphically, ordination major axis sample scores reveal two increasing-decreasing patterns in water depth that fit well with the T-R cycles previously identified. Paleobathymetric estimates combined with the vertical distribution of key ostracod groups (i.e., epiphytic taxa on sandy substrates vs. deep-sea mud related taxa) allow refining depositional trends, stratal stacking patterns and position of previously not well resolved sequence stratigraphic surfaces within each T-R cycle (e.g., Transgressive Surface-TS). Indeed, two rapid in-creases in water depth values mark the TSs that separate shallowing-upward, progradational (RST) from dee-pening upward, retrogradational (TST) stratal stacking patterns of shelf deposits. The TSs, which underline fine-grained successions dominated by deep-sea mud-lover taxa, are invariably constrained to the inception of in-terglacials Marine Isotope Stages (MIS) 21 and 19, identified within the VdM section by benthic foraminifera δ 18 O values. Within both the VdM T-R cycles, the deepest conditions (ca. 140 m of water depth) are invariably identified within the Neopycnodonte unit, slightly above the lightest δ 18 O intervals. The overlying decreasing bathymetric trend, coupled with shifts in ostracod ecological groups, allows to identify in the bryozoans li-thofacies the stillstand+falling of the relative sea-level, also tracked by a progressively heavier δ 18 O record. More stable paleobathymetric conditions (around 40-45 m of water depth) characterize the overlying silt-sand deposits dominated by epiphytic species and showing the heaviest δ 18 O values.

Impact of sedimentation, climate and sea level on marine sedimentary pyrite sulfur isotopes: Insights from the Valle di Manche section (Lower-Middle Pleistocene, southern Italy)

“…Previous work on the San Mauro sub-basin established the physical and sequence stratigraphies for the VdM section across two glacial-interglacial cycles (MIS 21-18, as defined by the reconstructed δ 18 O record of the benthic foraminifera Uvigerina peregrina in Capraro et al, 2017). The transitions between transgressive and regressive stratal stacking patterns and their stratigraphic relations were first established (e.g., Massari et al, 2002Massari et al, , 2007 and later refined using paleoenvironmental reconstructions from macrofaunal and ostracod fossil assemblages (Scarponi et al, 2014;Rossi et al, 2018). The age model used here (Table S1) combines chronostratigraphic control points identified in the same sample suite and reported in Capraro et al (2017) and Azzarone et al (2018), both of which were based on the δ 18 O stack of Wang et al (2010).…”

Pleistocene marine fish invasions and paleoenvironmental reconstructions in the eastern Mediterranean

“…This period had a strong impact on the Mediterranean marine ecosystems. For example, in the central Mediterranean, ostracods and molluscs responded synchronously to climate change during MIS21-19 (Rossi et al, 2018).…”

Depth as an overarching environmental variable modulating preservation potential and temporal resolution of shelly taphofacies

“…; Rossi et al . ). Canonical analyses together with variation partitioning revealed that the spatial extent accounts for an important fraction of taphonomic variation (Fig.…”

“…Although depth can be regarded as an environmental variable, it modulates other environmental variables by acting as a complex environmental gradient (Patzkowsky & Holland 2012). Depth acts as a spatially structured variable in both modern (Walton 1955;Smale 2008) and fossil assemblages (Scarponi & Kowalewski 2004;Redman et al 2007;Wittmer et al 2014;Rossi et al 2018). Canonical analyses together with variation partitioning revealed that the spatial extent accounts for an important fraction of taphonomic variation (Fig.…”