The endemic Mediterranean reef building vermetid gastropods Dendropoma petraeum complex (Dendropoma spp) and Vermetus triquetrus develop bio-constructions (rims) on rocky shorelines at about Mean Sea Level (MSL) and are therefore commonly used as relative sea-level (RSL) markers. In this study, we use elevations and age data of vermetid reefs to (1) re-assess the vertical uncertainties of these biological RSL indicators, and (2) evaluate the vertical growth rates along a Mediterranean east-west transect, in attempt to explain the differences found in both growth rates and uncertainties. In Israel, Differential Global Positioning System (DGPS) and laser measurements relative to the local datum show that the reef surfaces mainly occupy the upper intertidal zone with variations in elevation from +0.51 +/- 0.07 m to +0.13 +/- 0.05 m along the coast. However, in specific sites the vertical uncertainty exceeds the tidal range. In some places the local vermetid species D. anguliferum and V. triquetrus appear to alternate along the vertical rim profiles. This study documents a spatial variability of vertical growth rates, ranging from similar to 1 mm yr(-1) in Israel and Crete, to similar to 0.1-0.2 mm yr(-1) in NW Sicily and Spain. The order of magnitude of the difference in growth rates correlates with the east-west spatial thermal gradient of Sea-Surface Temperature (SST). Preferential skeleton deposition of D. petraeum and V. triquetrus measured by growth axis delta O-18 analysis shows that most calcification occurs at SST above the mean annual value. These findings indicate that vermetid reefs are a site-specific RSL indicator, displaying various vertical uncertainties and inner-structure complexities. Local data on the indicative range of vermetids are required when reconstructing relative sea-level changes using fossil vermetids.
The response to a beach face nourishment of the Terracina barred beach (Tyrrhenian sea, Italy) is analyzed based on a bi-weekly data set of timex video-images collected during a 34-month period (January 2008 - October 2010). Proxies for shoreline and sandbar crest positions were extracted from video-images and compared with topo-bathymetric surveys. During the first 17 months part of the nourished sediments were moved seaward and a shore-parallel linear single-bar system was restored. Bar dynamic was mainly influenced by on/offshore movements in relation to storms occurrence. A cluster of southerly extreme storms with maximum wave height of 4m sharply reshaped the nearshore morphology and a new double-barred system developed. A new inner bar generated close to the shoreline and the pre-existing one migrated 50m offshore. After this morphological reset the outer bar remained inactive and preserved a linear morphology for the whole analyzed period. On the contrary, the new inner bar dynamic was characterized by limited cross-shore displacements and high alongshore morphologic variability. During the last 5 months of observations a single barred-system was restored since the outer bar crest lost its morphologic evidence. As a consequence the inner bar moved 20m offshore and straightened.
A continuously cored borehole was used to analyse Holocene relative sea-level changes in the Pescara coastal plain, located along the central Adriatic coast (Abruzzo, central Italy). The core was retrieved from the uppermost 19m deposits, 600m from the present-day shoreline. Sedimentological and palaeontological analyses identified a transition from fluvial strata to brackish-water, lagoon and foreshore deposits. Five biological sea-level markers were sampled and their ages, constrained by AMS 14C dating, span between 2.39 and 7.68kacalBP. Heights (m above mean sea level) of the collected samples have been corrected, taking into consideration uncertainties of the vertical positioning with respect to palaeo-sea level. Vertical tectonic displacements have been evaluated through the comparison of relative sea-level data with the site-specific predicted Holocene sea-level curve. Correlations with available morphotectonic and stratigraphic data also were used. The results suggest negligible rates of vertical tectonic displacement during the Holocene, at least along a coastal strip of 40km located between Pescara and Sangro river mouths (Abruzzo).
Hyper/Multispectral data provide information about characteristic of natural and antropic surfaces. In order to retrieve the mineralogical species composing the Castel Porziano Beach (CPB), remote sensed data needs to be atmospherically corrected. In this work a new tool for the atmospheric correction for spaceborne EO data, based on MODTRAN and 6S codes, and developed on IDL/ENVI platform will be proposed and tested using NASA HYPERION and ASTER data. In this paper the capability to identify mineral association composing the sand of the CPB emerged beach, using hyperspectral data is shown. In order to define the mineralogical composition of the collected sample, SEM EMPA (Scanning Electron Microscopy and Electron MicroProbe Analyser) and optical polarizing microscopy analysis have been done. Results have been compared with 300 measurements performed directly on the CPB sand and 300 measurement acquired in the laboratory, both using an ASD-Fieldspec.