ABSTRACT The Laptev Sea Rift in the East Siberian continental margin plays an important role in the geodynamic models for the opening of the Eurasia Basin. The active Gakkel Ridge, which also represents the boundary between the North America and Eurasia plates, abruptly meets the continental margin of the Laptev Sea. On the continental shelf in the prolongation of the Gakkel Ridge, a rift developed since the Late Cretaceous/Early Cenozoic with the formation of five roughly north-south trending depocenters. To better understand the evolution of this rift, a basin modeling study was carried out with PetroMod® software. The modeled sections used in this study were developed on the basis of depth-converted reflection seismic sections. The sections cover the Anisin Basin in the north and the southeastern margin of the Ust´ Lena Rift in the south. The numerical simulations are supported by tectonic and sedimentological field data that were collected in outcrops during the CASE 13 expedition to the New Siberian Islands in 2011. For the Anisin Basin different scenarios were modeled with rift onsets between 110 Ma and 66 Ma. The results show that the present-day temperature field in the area of the Anisin Basin and at the southeastern margin of the Ust´ Lena Rift is characterized by horizontal, seafloor-parallel isotherms. Geohistory curves extracted from the 2D simulations indicate a twofold rift evolution with a stronger initial subsidence in the Late Cretaceous to Early Paleogene and a moderate subsidence in Late Paleogene and Neogene times. Based on the modeling results, an early rift onset around 110 Ma seems to be more realistic than a later one around 66 Ma.

Abstract The New Siberian Islands are affected by a number of Mesozoic tectonic events. The oldest event (D1a) is characterized by NW-directed thrusting within the South Anyui Suture Zone combined with north–south-trending sinistral strike-slip in the foreland during the Early Cretaceous. This compressional deformation was followed by dextral transpression along north–south-trending faults, which resulted in NE–SW shortening in the Kotelny Fold Zone (D1b). The dextral deformation can be related to a north–south-trending boundary fault zone west of the New Siberian Islands, which probably represented the Laptev Sea segment of the Amerasia Basin Transform Fault in pre-Aptian–Albian times. The presence of a transform fault west of the islands may be an explanation for the long and narrow sliver of continental lithosphere of the Lomonosov Ridge and the sudden termination of the South Anyui Suture Zone against the present Laptev Sea Rift System. The intrusion of magmatic rocks 114 myr ago was followed by NW–SE-trending sinistral strike-slip faults of unknown origin (D2). In the Late Cretaceous–Paleocene, east–west extension (D3) west of the New Siberian Islands initiated the development of the Laptev Sea Rift System, which continues until today and is largely related to the development of the Eurasian Basin.

Abstract The evolution of the global oceanic and atmospheric circulation systems has been affected by several forcing processes, with orbital variations being dominant on shorter geological time scales. Over longer periods of time (>10 Ma) the tectonic evolution of the solid Earth has been recognized as the major control on the development of the global climate system. Tectonic activity acts in one of two different ways to influence regional and global climate. The earliest solid Earth-climatic interaction recognized was the effect that the opening and closure of oceanic gateways had on the circulation patterns in the global ocean. Major effects on regional and sometimes global climate have been attributed to such changes, e.g. closure of the Isthmus of Panama ( Driscoll & Haug 1998 ). Since the late 1980s a second form of climate-tectonic interaction has been recognized, involving the growth and erosion of oro-genic belts. In this second category the Arabian Sea region must be considered the global type example.

Abstract In the northern Arabian Sea the Arabian, Eurasian and Indian Plates are in tectonic interaction with one another. We present interpretations of multichannel seismic profiles across the Makran sub-duction zone (which is part of the Eurasian-Arabian Plate boundary) and the transtensional Murray Ridge and Dalrymple Trough (which are part of the Arabian-Indian Plate boundary). We distinguish four megasequences in the sedimentary succession, which we correlate over the entire study area. Regional unconformities separate the megasequences and enable us to establish a common history of the region before Late Miocene time (c. 20 Ma). The Early Pliocene (c. 4.5 Ma) reopening of the Gulf of Aden caused a reorganization of the plates and subsequent tilting of the oceanic crust of the Arabian Plate toward the Makran subduction zone. This event is documented by the regional M-unconformity. Since that time, sedimentation on the Oman Abyssal Plain has been permanently separated from the Indus Fan by the Murray Ridge, on the northern end of which there has been no significant sedimentation.