Baffin Bay Composite Tectono-Sedimentary Element

Baffin Bay formed as a result of continental extension during the Cretaceous, which was followed by sea floor spreading and associated plate drift during the early to middle Cenozoic. Formation of an oceanic basin in the central part of Baffin Bay may have begun from about 62 Ma in tandem with Labrador Sea opening but the early spreading phase is controversial. Plate-kinematic models suggests that from Late Paleocene the direction of sea floor spreading changed to N-S generating strike-slip movements along the transform lineaments, e.g. the Ungava Fault Zone and the Bower Fracture Zone, and structural complexity along the margins of Baffin Bay. The Baffin Bay Composite Tectono-Sedimentary Element (CTSE) represents a 3-7 km thick Cenozoic sedimentary and volcanic succession that has deposited over oceanic and rifted continental crust since active seafloor spreading began. The CTSE is subdivided into 5 seismic mega-units that have been identified and mapped using a regional seismic grid tied to wells and core sites. Thick clastic wedges of likely Late Paleocene to Early Oligocene age (mega-units E and D2) were deposited within basins floored by newly formed oceanic crust, transitional crust, volcanic extrusives and former continental rift basins undergoing subsidence. The middle-late Cenozoic is characterized by fluvial-deltaic sedimentary systems, hemipelagic strata and aggradational sediment bodies deposited under the influenced of ocean currents (mega-units D1, C and B). The late Pliocene to Pleistocene interval (mega-unit A) displays major shelf margin progradation associated with ice-sheet advance-retreat cycles resulting in accumulation of trough-mouth fans and mass-wasting deposits products in the oceanic basin. The Baffin Bay CTSE has not produced discoveries although a hydrocarbon potential may be associated with Paleocene source rocks. Recent data have improved the geological understanding of Baffin Bay although large data and knowledge gaps remain.

Decratonization by rifting enables orogenic reworking and transcurrent dispersal of old terranes in NE Brazil

Dispersion and deformation of cratonic fragments within orogens require weakening of the craton margins in a process of decratonization. The orogenic Borborema Province, in NE Brazil, is one of several Brasiliano/Pan-African late Neoproterozoic orogens that led to the amalgamation of Gondwana. A common feature of these orogens is that a period of extension and opening of narrow oceans preceded inversion and collision. For the case of the Borborema Province, the São Francisco Craton was pulled away from its other half, the Benino-Nigerian Shield, during an intermittent extension event between 1.0–0.92 and 0.9–0.82 Ga. This was followed by inversion of an embryonic and confined oceanic basin at ca. 0.60 Ga and transpressional orogeny from ca. 0.59 Ga onwards. Here we investigate the boundary region between the north São Francisco Craton and the Borborema Province and demonstrate how cratonic blocks became physically involved in the orogeny. We combine these results with a wide compilation of U–Pb and Nd-isotopic model ages to show that the Borborema Province consists of up to 65% of strongly sheared ancient rocks affiliated with the São Francisco/Benino-Nigerian Craton, separated by major transcurrent shear zones, with only ≈ 15% addition of juvenile material during the Neoproterozoic orogeny. This evolution is repeated across a number of Brasiliano/Pan-African orogens, with significant local variations, and indicate that extension weakened cratonic regions in a process of decratonization that prepared them for involvement in the orogenies, that led to the amalgamation of Gondwana.

Sedimentary Dispersal and Accumulation in the oceanic basin, South China Sea, revealed by Sediment Budget

<p>South China Sea (SCS) is not only the crucial pathway for transporting terrigenous materials from Eurasia to the Western Pacific Ocean since the early Oligocene, but also the dominant accumulation and preservation place as a result of limited material exchange between the semi-closed oceanic basin and the open ocean since the middle Miocene. Diverse factors, including global climate changes, eustatic sea level change, regional and local tectonic events, et al., controlled the sedimentary dispersal and accumulational patterns in the oceanic basin of the SCS, which can be revealed by the calculation of sediment budget at different geological times, as the sediment budget can illustrate directly the sediment influx, storage, loss in a basin system <em>(Hapke et.al, 2010).</em></p><p>By interpreting the multichannel seismic profiles covering the whole oceanic basin with constraints from International Ocean Discovery Program (IODP) Expeditions 349, 367 and 368, we reconstructed the sequence stratigraphy framework of the study area, and then calculated the sedimentary budget at different geological time. This work aims to quantitate the sedimentary dispersal and accumulation in the oceanic basin for the first time.</p><p>Until now we have completed the sequence boundary identification and dating, as well as the division of sedimentary units of all multichannel seismic profiles. The grid data of different sequence boundaries have been obtained and posted on the bathymetric map, and by the time-depth conversion with appropriate function in different region referred from the drilling results of IODP expeditions, we have figured out the thickness of each sedimentary unit. In the following we will do the decompaction correction before calculating the sedimentary budget of the whole oceanic basin at different times. This work could increase our understandings on the major controlling factors and possible material sources of the deposition process.</p><p> </p>

The Wave Climate of the Southern Ocean

An analysis of the wind and wave climate of the Southern Ocean is provided based on a combination of more than 30-years of satellite altimeter data plus insitu buoy measurements at 5 locations in the Southern Ocean. The analysis shows that the Southern Ocean is a unique environment where there are strong winds year-round which blow over exceptionally long distances. This unique situation results in spectral forms which are not seen in any other oceanic basin.

THE TECTONOSTRATIGRAPHY OF CYCLADIC BLUESCHIST UNIT ON SIKINOS AND SIFNOS: IMPLICATION FOR THE MESOZOIC TECTONIC SETTING

This study presents new results for the tectonostratigraphic configuration of the Cycladic Blueschist unit (CBU) in the islands of Sikinos and Sifnos. These results show that the observed tectonostratigraphy in CBU results from tectonic repetitions of a thinner sequence. Tectonic repetitions have been achieved by a series of largescale ductile thrusts that operated during burial and exhumation of CBU. Restoration of the tectonostratigraphy in both islands implies an original, pre-metamorphic sequence, which was made up by a volcano sedimentary complex at the base and an overlying carbonate-rich sedimentary succession. This Mesozoic protolithic sequence was possibly formed in a continental terrane or in a transitional domain between a continental terrane and an oceanic basin. We suggest that the Mesozoic protolith of the CBU was formed in an incipient oceanic basin rather than a mature ocean like Pindos Ocean. This incipient oceanic basin was developed either along south part or along the north margin of Pelagonian microcontinent.