Palaeoenvironmental control on sediment composition and provenance in the late Quaternary deltaic successions: a case study from the Po delta area (Northern Italy)

Abstract

Accumulation of continental, deltaic and shallow-marine sediments in the Po River coastal plain preserves a record of the Late Quaternary sea-level changes and shoreline migrations. The palaeoenvironmental evolution of this area and the changes in composition and provenance of sediments have been investigated through integrated sedimentological, micropalaeontological (mainly foraminifers) and geochemical analyses of core S1, from the southern part of the Po River delta, within a chronological framework supported by radiocarbon dating and correlations with adjacent core sequences.Eleven lithofacies, grouped into five facies associations, and four palaeontological assemblages provide the basis to define the palaeoenvironmental reconstruction of this succession consisting, from the base to the top, of: (i) continental sediments accumulated during the Late Pleistocene; (ii) back-barrier sediments marking the onset of Holocene sea-level rise; (iii) transgressive sands deposited during the rapid landward migration of a barrier-lagoon system; (iv) shallow-marine and prodelta sediments with faunal associations indicating a gradual approach to the Po River mouth; and (v) sub-recent delta front sands that form a considerable portion of the present coastal plain.Bulk chemical composition of sediments shows remarkable relationships with palaeoenvironments and locally improves facies characterizations. For example, they reveal carbonate leaching that emphasizes the occurrence of palaeosols in continental deposits or record enrichments in loss on ignition, S and Br, diagnostic of organic-rich layers in back-shore sediments. Selected geochemical elements (e.g. Mg and Ni) are particularly effective for the recognition of sediment provenances from the three main source areas observed in the subsurface deposits of the Po River coastal plain (e.g. Apenninic rivers, North Adriatic rivers and Po River). An Apenninic provenance is observed in continental and back-barrier sediments. A North Adriatic provenance characterizes the transgressive sands and the shallow-marine deposits; a significant Po River provenance is recorded in sediments related to the onset of the prodelta environment, confirmed by foraminiferal assemblages indicating remarkable increase in fluvial influxes.

New insights on late Quaternary palaeogeographic setting in the Northern Adriatic Sea (Italy)

“…For this reason, this source can be distinguished by the low Ni/Mg ratio (8-15). On the other hand, high values of the Ni/Mg (50-65) ratio are typical of Po sediments, either from present-day fluvial bottom sediments (Dinelli and Lucchini, 1999;Amorosi et al, 2002;Vignati et al, 2003) or Holocene marine sediments from boreholes (Amorosi et al, 2002;Curzi et al, 2006). The provenance signals are generally independent of the grain size of the sediments and have also been recognised in older sediments (up to 120 000 yr BP) in the area (Amorosi et al, 2007).…”

A multi-proxy approach to reconstructing sedimentary environments from the Sperchios delta, Greece

“…In addition, geochemical analyses (element concentration and ratios) along drilled cores of deltaic successions based on micro-x-ray fluorescence technique (µ-XRF) have also been used to characterize paleoenvironmental conditions (e.g. Curzi et al, 2006) and relatively short-term sedimentary changes (e.g. Vött et al, 2006Vött et al, , 2007.…”

Hydrogeochemical characterization of small coastal wetlands and forests in the Southern Po plain (Northern Italy)

“…), we applied the BEX index proposed by Stuyfzand (2008), which is valid for aquifers containing Dolomite. This mineral is the most common source of Mg besides sea water and is proved to be present in the study area (Curzi et al, 2006), therefore Mg should not be considered in the cation-exchange equation (Stuyfzand, 2008):…”

“…The water-table aquifer consists mainly of carbonaterich sands, dolomite (of both alpine and apenninic source) is also present in the aquifer (Marchesini et al, 2000;Curzi et al 2006).…”