Estructura de las sales messinienses y de los depósitos sincinemáticos asociados en el sector Noreste del surco de Valencia

Three main types of messinian salt accumulation structures are described from the interpretation of the ENIEPSA-MAP77 (1977) and WESTERN GEOPHYSICAL COMPANY OF AMERICA-MEDS (1973) seismic profiles of the northern area of the Valencia Trough (3'30'-5'30'E, 42'30'-40'00'N). Salt rollers, pillows and diapirs form three belts parallel to the contour of the Messinian salt limit. Salt rollers are located in the margin of the evaporitic basin, where the base of the salt has a dip of up to 5'. The extension achieved in the salt rollers area is accommodated by the roll-overs and the small pillows that develop basinward. The instability processes of the slope start the raft tectonics observed in this area. In the center of the basin, on the other hand, where the salt base is horizontal, bigger structures (pillows and diapirs) develop due to differential loading processes linked to the growing of the Valencia fan. Pillows are the most common structures and are separated from the diapirs of the deepest part of the basin by a syncline under which there is a salt weld. The diapirs are very scarce and show, as a main characteristic, the absence of secondary nm synclines. The evolution model for the whole basin, inferred from the study of the syn-hnematic sediments related to al1 the structures and the correlation of six guide reflectors through out the basin, is complex. The western margin oE the basin, where the salt rollers develop, shows that the salt rollers migrate upward in the slope and that the small pillows (sector 1) have a direction of migration from the bottom of the slope toward the basin. On the other han4 the big pillows (sector 11) and the scarce diapirs of the center of the basin show a landward migration from the deepest parts of the basin. The two pillow areas, sector 1 and sector 11, are separated by an area of no defonnation where the salt is 800 m thick which confirms the idea of no linkage between the two zones and two different origins for the margin and deep salt accumulation structures. The age of formation of these structures is lower Pliocene. Salt rollers are the first ones and the big pillows start growing later on. At present, the marginal salt rollers are inactive whereas the big pillows are still active as can be seen by the deformation they create at the sea bottom topography

The Geology of Chile

6 páginas.-- Book review of "The Geology of Chile", by Teresa Moreno and Wes Gibbons (eds.) (2007). Geological Society. London (United Kingdom). 414 pages, 286 figures including maps, charts and pictures; 27, 5 x 21 cm, ISBN 978-1- 86239-219-9 (hardback) and ISBN 978-1-86239-220-5 (softback).Peer reviewe

Estructura de las sales messinienses y de los depósitos sincinematicos asociados en el sector Noreste del surco de Valencia

Se describen tres tipos principales de acumulaciones salinas a partir de la interpretación de los perfiles de sísmica de reflexión de las campañas ENIEPSA-MAP-77 (1977) y WESTERN GEOPHYSICAL COMPANY OF AMERICA-MEDS (1973) en el sector norte del surco de Valencia. Los principales tipos de estructuras salinas son rollers de sal, almohadillas y diapiros que se disponen en tres cinturones paralelos al límite de la sal messiniense

Lithostratigraphy of volcanic and sedimentary sequences in central Livingston Island, South Shetland Islands

Livingston Island contains several, distinctive sedimentary and volcanic sequences, which document the history and evolution of an important part of the South Shetland Islands magmatic arc. The turbiditic, late Palaeozoic–early Mesozoic Miers Bluff Formation (MBF) is divided into the Johnsons Dock and Napier Peak members, which may represent sedimentation in upper and lower mid-fan settings, respectively, prior to pre-late Jurassic polyphase deformation (dominated by open folding). The Moores Peak breccias are formed largely of coarse clasts reworked from the MBF. The breccias may be part of the MBF, a separate unit, or part of the Mount Bowles Formation. The structural position is similar to the terrigenous Lower Jurassic Botany Bay Group in the northern Antarctic Peninsula, but the precise stratigraphical relationships and age are unknown. The (?) Cretaceous Mount Bowles Formation is largely volcanic. Detritus in the volcaniclastic rocks was formed mainly during phreatomagmatic eruptions and redeposited by debris flows (lahars), whereas rare sandstone interbeds are arkosic and reflect a local provenance rooted in the MBF. The Pleistocene–Recent Inott Point Formation is dominated by multiple, basaltic tuff cone relicts in which distinctive vent and flank sequences are recognized. The geographical distribution of the Edinburgh Hill Formation is closely associated with faults, which may have been reactivated as dip-slip structures during Late Cenozoic extension (arc splitting)

Chronic Neospora caninum infection and repeat abortion in dairy cows: a 3-year study

The serological status of Neospora was monitored in animals older than 6 months in a dairy herd with a 3-year history of prevalent N. caninum and N. caninum-associated abortions. The numbers of animals in the herd tested each year of the study period were 259, 222 and 231, respectively. A separate analysis was performed on the 122 animals persisting in the herd for the 3 years. The overall seroprevalence of N. caninum in the herd decreased from 31.7% in the first year to 24.8% in the second year and to 19.9% in the third year of the study, while the overall abortion rate decreased from 20.6% in the first year to 5.5% in the second year, and 9.9% in the third. These decreases occurred in response to control measures adopted from the second year onwards, such as culling Neospora-seropositive aborted animals and inseminating Neospora-seropositive dams with beef bull semen. Of the total number of abortions recorded in seropositive animals, 51% were repeat abortions that occurred in 36.8% of the animals with a previous history of abortion. The initial seroprevalence of Neospora in the 122 animals followed for the 3 years was 18%, increasing to 21.3% in the second and third years. Seroconversion only occurred in four animals during the second and third years of the study and abortion occurred only in seropositive individuals. Of the total number of abortions recorded in the 122 animals, 61.5% were repeat abortions that occurred in 26.7% of the animals with a previous history of abortion. These results indicate that Neospora seropositivity can be very stable through time and N. caninum infected cows can show a high rate of repeat abortions. The present data reinforce the idea that annual serological screening for Neospora can be an effective and rapid method of detecting N. caninum infection, such that control measures can be established at the farm level