The Late Glacial-Holocene record from Central Adriatic Sea: Paleoenvironmental reconstruction based on benthic foraminiferal assemblages

New micropaleontological data coming from three cores collected on the meso-Adriatic continental shelf (Vasto area) are studied. Comparisons to foraminiferal assemblages and radiocarbon dates previously collected from cores in the San Benedetto del Tronto and Tremiti areas allow the correlation of patterns observed in shallow water areas with those in deeper parts of the basin. We focused on the response of benthic foraminifera during the Holocene high-stand, corresponding to the installation of the recent sedimentary and trophic system. An influence of anthropogenic impacts cannot be ruled out; its effects consist of a depletion of oxygen level with a consequent modification of the structure of benthic foraminiferal assemblages. During the glacial/post glacial cycle, three phases, characterized by a total of six foraminiferal biofacies including different species assemblages were recognized. The first phase, from 14 kyr BP to 11 kyr BP, corresponds to the Bolling/Allerod and Younger Dryas cold event, before the Holocene sea-level rise. During this phase, the continental shelf was characterized by an infralittoral environment with productive waters owing to the proximity of the Po river delta at the edge of the Mid-Adriatic Deep. The second phase, from 11 kyr BP to 4 kyr BP, represents the Holocene sea-level rise and is characterized by a condensed sedimentation spread over the entire basin. The third phase corresponds to the Holocene high-stand, during which time the modern current system became established. During this phase, the eastern portion of the shelf underwent to the central part of the mud-belt, corresponding to the sub-recent conditions. Recent eutrophication resulting from human activities over the last few centuries is evidenced by frequency fluctuations of typically opportunistic taxa such as Nonionella turgida and Epistominella vitrea. (C) 2013 Elsevier Masson SAS. All rights reserved

Paleoenvironmental reconstruction of Late Quaternary succession by foraminiferal assemblages of three cores from the San Benedetto del Tronto coast (central Adriatic Sea, Italy)

New shelf records based on benthic foraminiferal assemblages allowed reconstruction of the paleoenvironmental evolution of the central Adriatic Sea during the Late Quaternary. Four distinct assemblages related to four different environments were identified based on multivariate analyses (cluster analysis and principal component analysis): circalittoral, shallow water with vegetation, deltaic and shallow marine with riverine influence. Two main phases were recognized by comparing the study area with the northern and southern portion of the Adriatic basin. The first phase was characterized by the last glacial lowstand or the beginning of the last Pleistocene transgression. The foraminiferal assemblage distribution was controlled by sea-level changes and by the location of the ancient Po River delta likely placed at the northern margin of the Mid-Adriatic Deep. A subsequent deepening from a deltaic to normal marine shallow water environment occurred. River supply decreases consistently from the bottom to the top of the cores due to the northern migration of the Po delta. The second phase, which occurred during the Holocene, was characterized by sea-level stabilization and modern water circulation pattern; circalittoral foraminiferal assemblage typical of the outer mud-belt developed during this second phase. © 2011 Elsevier Ltd and INQUA

Late Quaternary paleoenvironmental reconstruction of the Tremiti structural high (Central Adriatic Sea) from benthic foraminiferal assemblages

Foraminiferal analyses carried out on the VTR01/8 core (Tremiti Islands, Adriatic Sea) lead to the reconstruction of the paleoenvironmental evolution of the area. Although the core site is located at about 1000 km from the Po delta, this study shows that the installation of the recent sedimentological and run-off system (with a shore parallel clay-belt) is similar to that described at sites much closer to the Po delta. The statistical analysis singled out four associations that correspond to four distinct environments. The ecological preferences of the most abundant taxa that characterize each environment reveal that from the bottom of the core to - 50 cm, there is a slight increase of the water depth after which the water depth increases until the present level. Association A (that comprises subclusters A1, A2 and A3) is characterized by shallow-water taxa (e.g., Ammonia beccarii, Quinqueloculina spp. and Elphidium granosum) showing that in the past an infralittoral environment typified the Tremiti High. The subclusters of Association A show that during the deposition of the lower part of the core there had been an alternation of phases characterized by different degrees of riverine influence: the site was at first under the influence of river outflow (A2) that later bypassed the core site (A3) and then came back, although located further away than before (A1). With the rising of the sea level, the Tremiti High became only marginally affected by river influence because the core site is located at a considerable distance from the Po outlets and seaward with respect to the center of the modern mud-belt. As a matter of fact, association B (Bulimina marginata, Cassidulina carinata and Textularia spp.), which starts at 46 cm, shows the typical characteristics of the modern mud-belt outer-shelf assemblage, although the presence of opportunistic species is limited by the distant position with respect to the Po delta