Plate Kinematics and Conjugate Margins Interactions: The Example of Central and North Atlantic Oceans
Jean-Claude Sibuet1, Stephane Rouzo2, and Shiri Srivastava3
1Institute of Geophysics, National Central University, Chung-Li, Taiwan.
2SRC, Plouzane, France.
3Geological Survey of Canada, Bedford Institute of Oceanography, Dartmouth, NS, Canada.
Without a combined analysis of plate kinematics and conjugate margins, basin formation and early opening or combined interpretation of refraction and reflection data, it is almost impossible to be confident in the interpretation of a specific set of data, even if this set of data is of state-of-the-art quality. A well-known example is the crustal interpretation of MCS data, which is highly dependent on the associated wide-angle and refraction data.
In this talk we will focus on the kinematics of the Central and North Atlantic, mostly between the North America (NA), the Africa (AF), the Meseta (MES) and the Iberia (IB) plates and wide-angle seismic data collected between the MES and NA plates. It is well known that there is an asymmetry in the opening of the Central Atlantic, in particular during the East Coast Magnetic Anomaly (ECMA) and Blake Spur Magnetic Anomaly (BSMA) (190-170 Ma) period. For many authors, the BSMA corresponds to an eastern ridge jump at about 170 Ma leaving crust from both ridge flanks between ECMA and BSMA. Wide-angle and refraction data acquired off Nova Scotia demonstrate the presence of a 90-km wide high velocity body, interpreted as a stripe of exhumed mantle which is absent on the Moroccan side. As the kinematics between ECMA and BSMA is well controlled (Labails et al., 2010), a major eastward ridge jump occurred at 177 Ma (Toarcian), i.e. after the formation of the high velocity body and not at chron BSMA (170 Ma) as suggested previously. Similarly, by looking at the detailed salt distribution on the Nova Scotia margin, it was established that an absence of allochtonous salt in the Huron Basin was corresponding to a region of allochtonous salt off Morocco, lying westward of both the thinned continental crust domain and the newly defined northern prolongation of the ECMA conjugate magnetic lineation. This discovery suggests the existence of another eastward ridge jump, which occurred at the end of the rifting episode (chron ECMA, 190 Ma). These two examples show that, by using combined sets of pertinent data, it is possible to constrain not only the detailed kinematics but also to explain peculiarities, which have no straightforward explanations.
It is this kind of problems, which are generally not tackled by the oil industry community, that we want to address.
Labails, C., J.-L. Olivet, D. Aslanian, and W. R. Roest, 2010. An alternative early opening scenario for the Central Atlantic Ocean, Earth Planet. Sci. Lett., 297, 355-368.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.������������������������������������������������������������