Lithospheric structure in Central Eurasia derived from elevation, geoid anomaly and thermal analysis

<p>We present new crustal and lithospheric thickness maps for Central Eurasia from the combination of elevation and geoid anomaly data and thermal analysis. The results are strongly constrained by numerous previous data based on seismological and seismic experiments, tomographic imaging and integrated geophysical studies. Our results indicate that high topography regions are associated with crustal thickening that is at a maximum below the Zagros, Himalaya, Tien Shan and the Tibetan Plateau. The stiffer continental blocks that remain undeformed within the continental collision areas are characterized by a slightly thickened crust and flat topography. Lithospheric thickness and crustal thickness show different patterns that highlight an important strain partitioning within the lithosphere. The Arabia–Eurasia collision zone is characterized by a thick lithosphere underneath the Zagros belt, whereas a thin to non-existent lithospheric mantle is observed beneath the Iranian and Anatolian plateaus. Conversely, the India–Eurasia collision zone is characterized by a very thick lithosphere below its southern part as a consequence of the underplating of the cold and stiff Indian lithosphere. Our new model presents great improvements compared to previous global models available for the region, and allows us to discuss major aspects related to the lithospheric structure and acting geodynamic processes in Central Eurasia. </p

Lower plate geometry controlling the development of a thrust-top basin: the tectonosedimentary evolution of the Ofanto basin (Southern Apennines)

<p>The Ofanto basin is a Pliocene–Pleistocene thrust-top basin that formed with an unusual east–west orientation along the frontal part of the Southern Apennine Allochthon during the latest stages of tectonic transport. Its tectonic and sedimentary evolution was studied integrating field surveys, biostratigraphic analyses and the interpretation of a large seismic grid. Well data and seismic interpretation indicate that a large east–west-trending normal fault underlies the northern margin of the basin, displacing the Apulian carbonates that form the foreland and the footwall of the Southern Apennine Allochthon. In our reconstruction the Ofanto basin formed at the rear of the bulge caused by buttressing of the Southern Apennine Allochthon against this normal fault. In a second stage of contraction, the footwall of the Southern Apennine Allochthon was involved in deformation with a different trend from the normal faulting and buttressing. This caused eastward tilting of the basin and broad folding around its eastern termination. Good stratigraphic constraints permit the age of buttressing to be defined as Early Pliocene, and that of the shortening in the Apulian carbonates as Early Pleistocene. This study highlights the importance of early orogenic normal faults in conditioning the evolution of the frontal parts of orogenic wedges. </p

Basin architecture and growth folding of the NW Zagros early foreland basin during the Late Cretaceous and early Tertiary

<p>We present and use the chronostratigraphy of 13 field logs and detailed mapping to constrain the evolution of the early Zagros foreland basin, in NW Iran. Large foraminifera, calcareous nannofossil, palynological and ⁸⁷Sr/⁸⁶Sr analysis supplied ages indicating a Campanian–early Eocene age of the basin infill, which is characterizd by a diachronous, southwestward migrating, shallowing upwards, mixed clastic–carbonate succession. Growth synclines and local palaeoslope variations indicate syndepositional folding from Maastrichtian to Eocene time and suggest forelandward migration of the deformation front. We also illustrate the basin architecture with a synthetic stratigraphic transect. From internal to external areas, time lines cross the formation boundaries from continental Kashkan red beds to Taleh Zang mixed clastic–carbonate platforms, Amiran slope deposits and basinal Gurpi–Pabdeh shales and marls. The foreland basin depocentres show a progressive migration from the Campanian to Eocene (<em>c</em>. 83–52.7 Ma), with rates of <em>c</em>. 2.4 mm a⁻¹ during the early–middle Palaeocene (<em>c</em>. 65.5–58.7 Ma) increasing to <em>c</em>. 6 mm a⁻¹ during the late Palaeocene–earliest Eocene (<em>c</em>. 58.7–52.8 Ma). Coeval subsidence remained at <em>c</em>. 0.27 mm a⁻¹ during the first 12.7 Ma and decreased to <em>c</em>. 0.16 mm a⁻¹ during the last 4.2 Ma of basin filling. Finally, we integrate our results with published large-scale maps and discuss their implications in the context of the Zagros orogeny. </p