New data on the Pleistocene of Trani (Adriatic Coast, Southern Italy)

Along the Apulian Adriatic coast, in a cliff south of Trani, a succession of three units (superimposed on one another) of marine and/or paralic environments has been recognised. The lowest unit I is characterised by calcareous/siliciclastic sands (css), micritic limestones (ml), stromatolitic and characean boundstones (scb), characean calcarenites (cc). The sedimentary environment merges from shallow marine, with low energy and temporary episodes of subaerial exposure, to lagoonal with a few exchanges with the sea. The lagoonal stromatolites (scb subunit) grew during a long period of relative stability of a high sea level in tropical climate. The unit I is truncated at the top by an erosion surface on which the unit II overlies; this consists of a basal pebble lag (bpl), silicicla - stic sands (ss), calcareous sands (cs), characean boundstones (cb), brown paleosol (bp). The sedimentary environment varies from beach to lagoon with salinity variations. Although there are indications of seismic events within the subunits cs, unit II deposition took place in a context of relative stability. The unit II is referable to a sea level highstand. Unit III, trangressive on the preceding, consists of white calcareous sands (wcs), calcareous sands and calcarenites (csc), phytoclastic calcirudite and phytohermal travertine (pcpt), mixed deposits (csl, m, k, c), sands (s) and red/brown paleosols (rbp). The sedimentation of this unit was affected by synsedimentary tectonic, attested by seismites found at several heights. Also the unit III is referable to a sea level highstand. The scientific literature has so far generally attributed to the Tyrrhenian (auct.) the deposits of Trani cliff. As part of this work some datings were performed on 10 samples, using the amino acid racemization method (AAR) applied to ostracod carapaces. Four of these samples have been rejected because they have shown in laboratory recent contamination. The numerical ages indicate that the deposits of the Trani cliff are older than MIS 5. The upper part of the unit I has been dated to 355±85 ka BP, thus allowing to assign the lowest stromatolitic subunit (scb) at the MIS 11 peak and the top of the unit I at the MIS 11-MIS 10 interval. The base of the unit II has been dated to 333±118 ka BP, thus attributing the erosion surface that bounds the units I and II to the MIS 10 lowstand and the lower part of the unit II to MIS 9.3. The upper part of the unit II has been dated to 234±35 ka BP, while three other numerical ages come from unit III: 303±35, 267±51, 247±61 ka BP. At present, the numerical ages cannot distinguish the sedimentation ages of units II and III, which are both related to the MIS 9.3- MIS 7.1 time range. However, the position of the units, superimposed one another, and their respective age, allows us to recognise a subsidence phase between MIS 11 and MIS 7, followed by an uplift phase between the MIS 7 and the present day, which led the deposits in their current position. This tectonic pattern is not in full agreement with what is described in the literature for the Apulian foreland.

Chemical composition of hydrothermal carbonates and barites from the Deryugin Basin, Sea of Okhotsk

Data on hydrothermal activity in the Deryugin Basin (Sea of Okhotsk) are reviewed. Barites and carbonates found in sediment cores sampled at feet of hydrothermal mounds were subdivided into recycled and authigenic types. Recycled minerals were represented by crystals and aggregations of travertine-like barite and fragments of barite and carbonate tubes. Authigenic formations included: (1) carbonate nodules; (2) barite micronodules; (3) transparent colorless barite that generated numerous small nests and filled cavities in sediments; (4) yellow barite formed thin (0.5 mm) veins; and (5) white barite cemented small aggregations of coarse-grained sediments. A detailed examination of formation processes of authigenic minerals in the bottom sediment cores allowed to conclude that, there, hydrothermal activity is still going on today. This was confirmed by high methane concentration in near-bottom water above a field of hydrothermal barite minerals.

Age an origin of the "Mexican Onyx" at San Antonio Texcala (Puebla, Mexico)

A great variety of color banded CaC03 is known as „Mexican Onyx“, and is extensively used for ornamental purposes. Within the San Antonio Texcala mining district an area of about 24.000 m2 is covered by a thick travertine crust with a calculated volume of at least 2,8 x 1061. It originates from warm waters that emerge on young fissures and faults. It seems to be likely that the travertine formation is related to the hydrothermal activity of the Transmexican Volcanic Belt and to the seismicity of this zone. The deposit is built up by different travertine varieties. The main lithotypes are: (1) dense crystalline laminated travertine; (2) ray crystal travertine; (3) shrub layer travertine; (4) irregular porous travertine; (5) travertine breccia. Textural variation seems to be related to water temperature/distance from the emergence point, rapid or slow degassing of CO, and bacterial influence. At the moment, a light green banded variety (native sulfur impurities) is mined. It is the facture fill of a morphological prominent fissure-ridge travertine. U/Th data indicate, that the travertine has been deposited since at least 52 + 5 ka.

Central Algarve karst system tufa-related dynamics, Portugal.

Geomorphological mapping is a powerful instrument improving the geomorphological interpretation and understanding of the processes and forms used in landscape studies, with the ability of organizing different thematic layers in the same map. The presented map provide relevant information about the different geomorphological units of the central Algarve (i.e. the Carboniferous flysch mountains; the Barrocal, with marly and karstified subunits), where a karst system is prominent. Solution karst morphologies and large dry areas are common in the elevated areas of the Barrocal, suggesting deep circulation of groundwater. These recharge areas feed the perched aquifers of the area, where discharge is controlled by the impervious lithologies (clay-rich strata of the turbidites, marls and argilites) in the valley bottoms or other leaks in dammed aquifers. In springs related to the main aquifers tufa are actively being formed and, close coupled to spring location, different tufa depositional systems develop.