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Very high-resolution seismic profiles allow a sequence-stratigraphic analysis of the Holocene deposits off the Venice Lagoon. The succession is bounded at the base by an unconformity (sequence boundary), well recognizable in seismic profiles, which crops out at seaward locations. In the lower part of the Holocene succession, zones showing sub-horizontal and hummocky reflectors are separated by channelized deposits, interpreted as estuarine channel fills and distributary channel-levee systems. A sharp surface, climbing landward, truncates the lower Holocene deposits. This is overlain by a prograding shallow-marine wedge, which represents the upper part of the succession. This wedge consists of a regressive shoreface-shelf system and, locally, of ebb-tidal deltas off the lagoon inlets. The lower part of the Holocene succession is interpreted as a transgressive systems tract, deposited during the high-amplitude sea-level rise that followed the Last Glacial Maximum. A wave ravinement surface marks the marine ingression of the late transgressive phase, and is approximately coincident with the downlap surface in seismic profiles. The prograding shallow-marine wedge represents the highstand systems tract. During this latter phase, the rate of sediment supply outpaced that of creation of accommodation. The variable thickness distribution of the TST documents important changes in the stratal architecture of the Holocene deposits along both depositional strike and dip, which may be in part due to antecedent basin physiography.

We present a general bathymetric map of Lago Fagnano, the largest ice-free lake of the Southern Hemisphere, located in the central part of the Tierra del Fuego Island. The map has been obtained compiling all the available bathymetric soundings and depth-converted high-resolution seismic profiles, collected in the course of several geophysical campaigns. The lake occupies a 110-km long, E-W trending tectonic depression within the southernmost tip of the Andean Cordillera, where the South America-Scotia plate boundary traverses the Tierra del Fuego Island. The map allows us to identify the main morpho-bathymetric features of Lago Fagnano. The lake floor is divided into two principal sectors of different water depths, separated by a main shoal located in the central part of the lake. Maximum water depth (206 m) is found in the eastern part, whereas water depths in the western half do not exceed 165 m. In this paper, we describe the geometry and the general morphological characteristics of the basin, which was generated by a combination of distinct tectonic processes, and later superposed by Late Quaternary glacial and glacio-lacustrine dynamic events. Fil: Zanolla, C.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Lodolo, E.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale ; Italia Fil: Lippai, Horacio Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentina Fil: Tassone, Alejandro Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentina Fil: Menichetti, M.. Università di Urbino; Italia Fil: Baradello, L.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Grossi, H. L.. Istituto Nazionale di Oceanografia e di Geofisica Sperimentale; Italia Fil: Hormaechea, Jose Luis. Estación Astronomica de Río Grande; Argentina

The occurrence of alternating dry/wet conditions in transitional environments, such as wetlands, deltas, and lagoons, usually challenges the use of traditional direct and geophysical surveys for comprehensive hydrogeologic investigations. Moreover, significant mixing between continental fresh groundwater and marine salty surface waters generally takes place in these flat coastal areas. Airborne electromagnetics (AEM) is a promising tool in this respect, as it provides, in a fast and cost effective manner, large-scale distribution of bulk electrical conductivities that can be used profitably to develop hydrogeologic models. The results of a SkyTEM AEM survey in the Venice Lagoon, Italy, show the capability of this technique to significantly improve the knowledge of the hydrogeologic setting of the lagoon and nearby coastland subsurface, irrespective of the different features characterizing the area. The environment consists of salt marshes, mud flats, shallows, tidal channels, islands, together with reclaimed farmlands crossed by natural watercourses and drainage channel networks. In particular, the AEM shows (i) the presence of fresh water (with resistivity larger than 20 Ω m) underneath the central part of the lagoon at depths from 10 to 25. m below m.s.l., (ii) the interface between different relevant stratigraphic units, e.g., the clayey layer bounding the Holocene-Pleistocene sedimentation, and (iii) the occurrence of areas with possible submarine fresh groundwater discharge. Moreover, the source and inland extent of the saltwater contamination in the shallow coastal aquifers along the southern margin of the lagoon are clearly revealed. AEM data were complemented with very high resolution seismic (VHRS) acquisitions. The integrated analysis of the two data sets allows distinguishing between lithostratigraphic heterogeneity and variability of the subsurface fluids. © 2011 Elsevier B.V.

An international archaeological and geophysical expedition was carried out to study Iron Age tombs of the Saka culture in southeastern Kazakhstan. Single-fold and multifold ground-penetrating radar (GPR) surveys, in two and two and a half dimensions, focused on the identification of burial chambers beneath the mound-shaped Saka tumuli, named kourgans. Primary objectives of the geophysical study were the testing and optimization of GPR techniques for studying this type of tomb and the reconstruction of subsurface images of use for the design of archaeological excavations. Single-fold GPR grids with line spacing ranging between 50 and 200 cm were obtained at each of the 13 sites selected. After identification of the sectors of major potential interest from data processing performed directly in the field and interpretation of the single-fold grids, multifold profiles with average 1200 per cent fold were designed and performed. Processing of the data focused on velocity analyses, pre-stack coherent noise attenuation by means of FK and KL filters, stacking and analysis of the instantaneous attributes of the complex radar trace. Multifold GPR data processing techniques achieved a substantial increment in the signal to noise ratio at most sites, allowed accurate depth conversions of the stacked profiles (average deviation of estimated target location from the actual target was less than 5% of total depth) and provided indications to identify the characteristic response from the target of interest through the joint interpretation of pre-stack gathers, velocity analysis and amplitude versus offset analysis. Interpretation of stacked sections and three-dimensional models obtained from the single-fold/multifold grid allowed the identification of a burial chamber located at an estimated depth of 140–150 cm, which was excavated successfully by the archaeological team. Further reflectors with similar characteristics are shown from other sites, which will be excavated by the next archaeological expeditions to the area. Copyright © 2001 John Wiley & Sons, Ltd.

A 2.5-D and 3-D multi-fold GPR survey was carried out in the Archaeological Park of Aquileia (northern Italy). The primary objective of the study was the identification of targets of potential archaeological interest in an area designated by local archaeological authorities. The second geophysical objective was to test 2-D and 3-D multi-fold methods and to study localised targets of unknown shape and dimensions in hostile soil conditions. Several portions of the acquisition grid were processed in common offset (CO), common shot (CSG) and common mid point (CMP) geometry. An 8×8 m area was studied with orthogonal CMPs thus achieving a 3-D subsurface coverage with azimuthal range limited to two normal components. Coherent noise components were identified in the pre-stack domain and removed by means of FK filtering of CMP records. Stack velocities were obtained from conventional velocity analysis and azimuthal velocity analysis of 3-D pre-stack gathers. Two major discontinuities were identified in the area of study. The deeper one most probably coincides with the paleosol at the base of the layer associated with activities of man in the area in the last 2500 years. This interpretation is in agreement with the results obtained from nearby cores and excavations. The shallow discontinuity is observed in a part of the investigated area and it shows local interruptions with a linear distribution on the grid. Such interruptions may correspond to buried targets of archaeological interest. The prominent enhancement of the subsurface images obtained by means of multi-fold techniques, compared with the relatively poor quality of the conventional single-fold georadar sections, indicates that multi-fold methods are well suited for the application to high resolution studies in archaeology.