New geophysical compilations link crustal block motion to Jurassic extension and strike-slip faulting in the Weddell Sea Rift System of West Antarctica

first_imgGondwana breakup changed the global continental configuration, leading to opening of major oceanic gateways, shifts in the climate system and significant impacts on the biosphere, hydrosphere and cryosphere. Although of global importance, the earliest stages of the supercontinental fragmentation are poorly understood. Reconstructing the processes driving Gondwana breakup within the ice-covered Weddell Sea Rift System (WSRS) has proven particularly challenging. Paleomagnetic data and tectonic reconstructions of the WSRS region indicate that major Jurassic translation and rotation of microcontinental blocks were a key precursor to Gondwana breakup by seafloor spreading. However, geophysical interpretations have provided little support for major motion of crustal blocks during Jurassic extension in the WSRS. Here we present new compilations of airborne magnetic and airborne gravity data, together with digital enhancements and 2D models, enabling us to re-evaluate the crustal architecture of the WSRS and its tectonic and kinematic evolution. Two provinces are identified within the WSRS, a northern E/W trending province and a southern N/S trending province. A simple extensional or transtensional model including ~ 500 km of crustal extension and Jurassic magmatism accounts for the observed geophysical patterns. Magmatism is linked with rifting between South Africa and East Antarctica in the north, and associated with back-arc extension in the south. Our tectonic model implies ~ 30 degrees of Jurassic block rotation and juxtaposes the magnetically similar Haag Block and Shackleton Range, despite differences in both Precambrian and Pan African-age surface geology. Although geophysically favoured our new model cannot easily be reconciled with geological and paleomagnetic interpretations that require ~ 1500 km of motion and 90 degrees anticlockwise rotation of the Haag-Ellsworth Whitmore block from a pre-rift position adjacent to the Maud Belt. However, our model provides a simpler view of the WSRS as a broad Jurassic extensional/transtensional province within a distributed plate boundary between East and West Antarctica.last_img read more

Bolivia To Collaborate with U.S. on Case of Former Police Chief Turned Drug Trafficker

first_img Bolivia will both seek assistance from and offer assistance to the United States in the investigation of a gang of traffickers led by a former director of the Bolivian anti-drug effort and former police intelligence chief, detained in Panama and extradited to the United States, an official source said on 1 March. “It’s worth cross-referencing information to verify the data; we’re going to exhaust all possibilities via the judicial route, via the diplomatic route,” Vice Minister of Social Defense Felipe Cáceres, the chief political figure responsible for the fight against drugs, indicated at a press conference. The minister affirmed that he will exhaust all efforts to clarify the situation of René Sanabria, a retired general and up to now the director of an intelligence office, who is a “leader of this network of police officers (engaged in trafficking) on an international scale.” Sanabria was detained the last week of February in Panama and subsequently extradited by the U.S. Drug Enforcement Agency to the United States, where a judge in Miami issued an international arrest warrant for the Bolivian police officer in December, on charges of selling drugs, and subsequently issued an indictment. Cáceres specified that as part of an information exchange, information just recently arrived at the Interior Ministry from the United States linking the former anti-narcotics head – in President Evo Morales’s current administration – with sales of cocaine, as well as the international arrest warrant. Right before his arrest, General Sanabria led an “intelligence and counterintelligence” unit in the fight against drug trafficking: the Intelligence and Information Generation Center (CIGEIN), dismantled following the police chief’s detention. Bolivia expelled the U.S. Drug Enforcement Agency at the end of 2008, accusing the agency of supporting a supposed right-wing plot against President Morales, although the White House denied the allegations. By Dialogo March 03, 2011last_img read more