The Orinoco Delta offshore is an exploration frontier along the northeast margin of the South American continent. The area is limited to the north by the transpressional southeast-Caribbean margin and to the south by the South American continent. Hydrocarbon production in this region has been ongoing for over half century, however, most of the studies in the more eastward deep-water areas have been unpublished due to the active exploration. New regional 2D seismic data, collected in 600-km-long sections out to the eastern limit of the southeastern Caribbean margin, reveal the region's major Mesozoic to Recent tectono-stratigraphic features. A chronostratigraphic framework for the Orinoco Delta offshore was defined by interpreting the deep seismic lines with sparse well and seismic information located in the continental margin. This study integrated valuable information in the deep water section with these results from: 1) Deep Sea Drilling Program (DSDP) sites 143-144 (Demerara Plateau-offshore Suriname), 2) Deep Sea Drilling Program (DSDP) Leg 77 (southeast Gulf of Mexico), 3) Ocean Drilling Program (ODP) Legs 156 and 171A (north of the Barbados Accretionary Complex), and 4) Ocean Drilling Program (ODP) Leg 159 (Cote d'Ivoire-Ghana, West Africa). These chronostratigraphic data assisted in establishing the tectonic and depositional history of the basin fill. Five regional sequences bounded by major unconformities define the margin's tectono-stratigraphic framework. These sequences are as follows: 1) megasequence 1: Late Jurassic syn-rift and post rift sequence associated with the Tethys Ocean opening, 2) megasequence 2: Early Cretaceous sequence related to the South Atlantic Ocean opening, 3) megasequence 3: Late Cretaceous-Paleocene passive margin sequence, 4) megasequence 4: Early Tertiary passive margin sequence, and 5) megasequence 5: foredeep sequence related to the Late Tertiary Caribbean compressional tectonics. The latest sequence represents a 3-5 km-thick Oligocene-to-Recent sediment column, whose architecture is influenced by local and regional tectonics, high rates of sediment supply from the Orinoco River drainage system, and major changes in sea level. The Orinoco Delta offshore area's tectono-sequence development reflects the region's transition from rift, to passive, to compressional margin history. The Tethys Ocean opening during the Late Jurassic resulted in non-marine to marine carbonate sedimentation in graben and half-graben structures over an extending continental to transitional crust. During the Early Cretaceous there are evidence of a transform margin in the northern Demerara Plateau, and creation of the pull-part basin in the deep Guyana Basin area, related to the South Atlantic Ocean opening. The drift phase of the newly formed Atlantic Ocean during the Late Cretaceous to the Lower Tertiary was controlled by changes in sea level. During the Neogene to Recent, structural deformation associated with of the transpressional Caribbean margin working in concert with the Orinoco Delta to dominate the basin architecture. The proto-Orinoco and Orinoco drainage systems have been the major sediment sources since the Middle Miocene. Late Miocene-to-Pleistocene-age growth faulting and shale mobilization dominate the recent and present-day basin fill. Marine currents and the area's active tectonics contributed to the complex sediment dispersion and deposition of the Quaternary Orinoco fan. Tectonics along the Caribbean margin results in two primary types of deformation activities. These activities are: 1) Minor reactivation of basement faults that influence the nature of the Neogene shelf edge architecture, and may even result in activation of deep mobile substrates (salt?) and 2) extensional and compressional deformation of the Neogene section above a common detachment surface, resulting in the development of growth faults, shale mobilization and diapirism, and even seafloor argilokinetic volcanism (observed in the eastern Trinidad and the Barbados Accretionary Prism).

West: -54.2031 East: -54.1843 North: 9.2827 South: 9.2714

Expedition: 14

Site: 14-143

Site: 14-144

Expedition: 156

Expedition: 159

Expedition: 171A

Expedition: 77

Provider: SEDIS Publication Catalogue

Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=2003-038730 (c.f. for more detailed metadata)

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