HR: 0800h
AN: T41A-0375    [Abstracts]
TI: Guiana's Basin, A Unique Setting with Two Break-up and Drift Unconformities and a Feature Hypothesized to be a Southern North Atlantic, Iceland Equivalent Atlantis
AU: * Kean, A E
EM: akeane@repsolypf.com
AF: Tectonophysics, 9315 Shady ane Cr., Houston, TX 77063, United States
AB: In the Guiana's Basin, two distinct Break-up/Drift Unconformities associated with thermal doming, rifting, cooling, compressing and drifting of plates were identified and mapped. The earliest unconformity 1) Mid-Jurassic-aged separation of North/Central America from Western Europe/North Western Africa and the latest unconformity 2) Albian-aged separation of Central West Africa from Central Northern South America, exist here. What complicates the interpretation of the plate motion is the amount of overburden deposited post Albian time on both sides of the ridge separating the African and the South American plates. To the east, the Niger River pushed out 5-20 km of sediments on top of the drift unconformity. In the Guiana's Basin the sedimentation is only about 5-10 km of sedimentation therefore it is easier to image and interpret the geologic history. Through a synthetic well to seismic tie, a correlation of new biostratigraphic data from a well spud in Nov. 1977 and TD'ed in June of 1978 by Esso, was incorporated into the regional geologic interpretation. The interpretation based on this data was that the timing of the opening of the South Atlantic was synchronous with that of the North Atlantic. The feature of interest closely resembles a buried volcanic landmass. It just happens to be located in the area hypothesized as the Mid Jurassic spreading center related to a hotspot, after Pindell and Kendall, March 2005. Interpretation and conclusions for this study are based on 1999 and 2004 vintages of 2D seismic data and a new interpretation of the biostratigraphy. Additionally, gravity and magnetic data along with regional subsidence modeling and a tectonic evaluation study supports these conclusions. On several 2D seismic lines from the area, a deep volcanic feature can be seen and interpreted to exist in Mid Jurassic time. This feature is similar in portion to Iceland the volcanic island currently residing in the middle of the North Atlantic Ocean. Today in the Guiana's Basin the feature identified on seismic is now deeply buried. We would content that this paleo volcanic "Island" produced some 180 mybp has since disappeared from the face of the Earth through normal subsidence processes. Therefore, what had evolved in a similar way to the Iceland we now know, has since disappeared much the same as the fictional city of Atlantis. What makes this area unique is the presence of two distinct unconformities and our ability to image them with conventional 2D seismic data.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8125 Evolution of the Earth (0325)
DE: 8157 Plate motions: past (3040)
DE: 8169 Sedimentary basin processes
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: 2007 Fall Meeting