LITHOBIOTOPES OF THE NEMEGT GOBI BASIN

Three distinct but overlapping dinosaur-dominated faunas characterize the Upper Cretaceous Djadokhta, Baruungoyot and Nemegt formations of the Nemegt Basin of Mongolia. Documented faunal differences cannot be explained easily by temporal succession, but can be understood in the light of physical processes controlling life, death, and burial of taxa. The stratigraphy of the Gobi Desert region records tectonically driven geometries, clearly documenting preservational processes different than those acting in most other dinosaur-dominated beds worldwide. Small, asymmetric tectonic grabens were filled with Upper Cretaceous, dinosaur bearing deposits showing asymmetric distributions of facies, here termed Lithobiotopes. The water-lain fluvial and alluvial plain facies of the Nemegt Lithobiotope supported and preserved a fauna dominated by gigantic dinosaurs, but had a preservational bias against smaller animals. The Nemegt passed laterally into interdune facies of the Baruungoyot Lithobiotope, which represented a hostile environment for large species, but preserved smaller animals. This in turn passed laterally into the aeolianite facies of the Djadokhta Lithobiotope, which is characterized by remains of small dinosaurs and a rich fauna of other animals. The Nemegt Gobi Basin can be visualized as an oasis with a central pond supplied with water from ephemeral channels and surrounded by a semi-arid alluvial plain and dune fields.

Abandoned Mine Tailings Affecting Riverbed Sediments in the Cartagena–La Union District, Mediterranean Coastal Area (Spain)

This study presents the results of the geoenvironmental characterization of La Matildes riverbed, affected by mine tailings in the Cartagena–La Unión district, Murcia (southeast Spain). Soils and riverbeds in this area are highly polluted. Two Electrical Resistivity Imaging (ERI) profiles were carried out to obtain information about the thickness of the deposits and their internal structure. For the mine tailings deposits of La Murla, a tributary of the El Miedo riverbed, the geophysical method imaged two different units: the upper one characterized by low resistivity values and 5–8 m thickness, correlated with the mine tailings deposits; and the lower more resistive unit corresponding to the Paleozoic metasediments bedrock. The ERI profile transverse to the Las Matildes dry riverbed revealed the existence of three different units. The uppermost one has the lowest resistivity values and corresponds to the tailings deposits discharged to the riverbeds. An intermediate unit, with intermediate resistivity values, corresponds to the riverbed sediments before the mining operations. The lower unit is more resistive and corresponds to the bedrock. Significant amounts of pyrite, sphalerite, and galena were found both in tailings and riverbed sediments. The geochemical composition of borehole samples from the riverbed materials shows significantly high contents of As, Cd, Cu, Fe, Pb, and Zn being released to the environment. Mining works have modified the natural landscape near La Unión town. Surface extraction in three open-pit mines have changed the summits of Sierra de Cartagena–La Unión. Rock and metallurgical wastes have altered the drainage pattern and buried the headwaters of ephemeral channels. The environmental hazards require remediation to minimize the environmental impact on the Mar Menor coastal lagoon, one of the most touristic areas in SE Spain.

The hunter-gatherer site BES II (Jacaré-Guaçu River low terraces, central Sao Paulo state, Brazil): Interface with geomorphical and environmental fluctuations of the Pleistocene-Holocene transition

The lithic site Boa Esperança II (BES II), in the São Paulo segment of the Brazilian Plateau, next to the boundary between the cities of Araraquara (SP) and Boa Esperança do Sul (SP), presents a collection of almost 2,000 lithic artifacts (predominantly chert and sandstone), being interpreted as a settlement of diversified functions with possibly continuous or successive occupation. In this work, we approach the site based on interface of its insertion in the regional physical-environmental context - with emphasis on the interface with relief frames, surface structure study and estimated geomorphic sequences of the alluvial plain of Jacaré-Guaçu river - and techno-typological analysis. It was verified that the BES II artifacts are distributed along vertical profiles and relief pictures lined by records that mark the transition from semi-arid conditions to others of increasing humidity, successive oscillations of base levels and modifications of fluvial regimes (ephemeral channels passing to perennial channels of different hydrological meandrings patterns), indicating that human occupation has dealt with conditions of quite distinct landscapes between the Late Pleistocene and the Holocene. Local lithic industry would have taken advantage of attributes derived from these modifications in the landscape over time - in particular the exposure of gravels of large river pebbles deposited by torrential ephemeral channels. The past abundance of raw material of fluvial origin would have contributed to the location of the site in the regional geomorphological context, as well as for a lithic assemblage based on the production of large unipolar flakes. We observed in the correlations between the position of artifacts, geomorphical and pedological data, OSL and Carbone-14 dates at archaeological levels, elements that allow us to discuss considering BES II as an archaeological site to integrate the interval of the Pleistocene-Holocene transition and to had interfaces with the geomorphological and environmental changes of such time. The archaeological implications of the issue and the fact that only one dating of photoluminescence has been reported from the deepest level of the site (basal gravel layer) emphasize the need for new, denser and more diversified studies.