This site lies between Sites 900 and 899 where coring reached basement during Leg 149, on the crest of a 7-km-wide north-south basement high crossed by three E-W lines and one N-S line. The high appears to be a fault block bounded to the west by an oceanward-dipping normal fault and underlain by a sub-horizontal reflector (detachment fault?), 1.5 s below the crest of the high, that intersects the top of basement south of the site. The basement cores will serve to discriminate among the variety of models postulated for the development of the OCT.
The N-S crossing of this site, plus a further E-W crossing of the broad high on which it lies, reveal that the high has a trend somewhat west of north and shoals quite rapidly northward; the high could conceivably represent the southward continuation of the Vasco da Gama Seamount south of the Iberia Abyssal Plain. The objective of the site is to determine the westward edge of continental crust and to establish the petro-structural evolution of the continental crust and the spatial relationships between upper lithospheric levels (continental crust) and deeper levels (gabbros of Site 900).
This site lies on a tilted fault block of probable continental crust that is capped by tilted transparent syn- or prerift sediments. The plan is to drill to the top of the transparent layer and then to core down to the underlying basement. The objectives of the site are the same as those at Site IBERIA08A.
This site lies over an elongated margin-parallel basement ridge that lies about 15 km east of the crest of the J magnetic anomaly and 20 km west of the peridotite ridge. Here, attempts to model the magnetic anomalies by seafloor spreading predict the presence of ca. 130 Ma oceanic crust. The objective of the site is to sample the early-formed oceanic crust. Samples from this site are expected to provide definitive evidence of the oceanic nature of the crust immediately west of the peridotite ridge and may enable the seafloor-spreading model to be verified. They will also yield the, possibly unusual, chemistry of the thin crust formed by the earliest magma-starved seafloor spreading and provide valuable petrological information about initial melt production following continental break up at a nonvolcanic margin.
This site, already drilled and cored during Leg 149, lies over a tilted fault block capped by a layer of tilted transparent shallow-water sediments of Late Jurassic (Tithonian) age. It exhibits an almost identical geometry on seismic profiles to Site IBERIA08B and the scientific objectives are the same. Because Site IBERIA08B lies west of the major, deeply penetrating north-northeast fault bounding Site 901 this latter site has a lower priority.
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