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

Abstract

This paper presents an integrated approach to assess Holocene environmental changes in the Sperchios delta, Sperchios rift, central Greece. A multidisciplinary study was carried out applying established analytical methods as well as exploring new techniques to detect past environmental conditions in a fluvio-deltaic depositional system. A series of six deep boreholes, up to 50 m long, and four shallow cores, up to 6 m long, from across the delta plain, were studied in detail. Sedimentary facies were defined by changes in grain size and macro-and microfaunal composition. Variability in mineral magnetic composition documented by changes in bulk magnetic susceptibility (χ and χ 77K /χ 293K ) and remanence parameters (S −300 and σARM/σSIRM ratios), as well as down-core elemental variations obtained by scanning micro-x-ray fluorescence (µ-XRF), provide constraints on the depositional changes related to the evolution of the Sperchios delta. Correlations between elemental data derived by µ-XRF analyses and grain size were also analyzed and used to further constrain the facies interpretation. Overall, these Holocene sediments reveal a transgressive-regressive succession overlying pre-transgressive terrestrial deposits of Late Pleistocene-Early Holocene age. Furthermore, 13 new 14 C radiocarbon dates constrain the transgression rate to be ~3.5 m/yr for the Early Holocene and the regression rate to be ~1 m/yr for the Late Holocene. The Sperchios delta plain developed when the rate of sea-level rise decreased ~6000 cal. yr BP as it has been proposed for the broader area of Aegean Sea. This study demonstrates that the combination of techniques used here provides a powerful way to map out paleoenvironmental changes and thus the 3D stratigraphic architecture of Holocene sedimentary successions.

Source‐to‐sink analysis in an active extensional setting: Holocene erosion and deposition in the Sperchios rift, central Greece

“…We begin our analysis with the deltaic depositional system, where we have particularly good constraints (c.f. Pechlivanidou et al ., ), and work progressively upstream by analysing the onshore fluvial system and ultimately quantifying the upland sediment sources. These different components are then brought together in a mass balance calculation for the whole erosional‐depositional system in the Sperchios basin.…”

“…Red dots indicate the location of borehole drillings used to construct the Holocene stratigraphy of the delta along XX ’ transect, shown in Fig. b (from Pechlivanidou et al ., ). Yellow dots indicate the location of the additional borehole drillings used in this study to produce the 3D geometry of the transgressive surface ( TS ) shown in Fig.…”

“…Line indicating Sedflux2D modelled profile is also shown (see Figs and ). (b) The stratigraphic model of the Holocene Sperchios delta after Pechlivanidou et al ., (). Facies associations are indicated; FA 1: Fluvial, FA 2I: Coastal plain, FA 2 II : Back‐barrier lagoon, FA 3I: Prodelta, FA 3 II : Delta front, FA 4I: Open lagoon, FA 5I: Channel fill, FA 5 II : Floodplain.…”

“…a) indicate that they developed as a transgressive to regressive succession during the Holocene (Fig. b; Pechlivanidou et al ., ) and consist mainly of fine‐grained sediments (i.e., ~60% silt). These deposits are ~50 m thick and overlie alluvial plain deposits of Late Pleistocene ‐ Early Holocene age (Pechlivanidou et al ., ).…”

“…b; Pechlivanidou et al ., ) and consist mainly of fine‐grained sediments (i.e., ~60% silt). These deposits are ~50 m thick and overlie alluvial plain deposits of Late Pleistocene ‐ Early Holocene age (Pechlivanidou et al ., ). Within this succession 14 C determinations indicate a marine transgression rate of approximately 3.5 m year −1 for the Early Holocene.…”