HR: 0830h
AN: T31F-0890    [PDF]
TI: Along-strike Variation in the Sandino Basin of Nicaragua and Implications for the Development of the Central American Forearc
AU: * Silver, E A
EM: esilver@es.ucsc.edu
AF: Earth Sciences Department, University of California 1156 High Street, Santa Cruz, CA 95064 United States
AU: Costa Pisani, P
EM: patrizia@hawaii.edu
AF: SOEST, University of Hawaii, Honolulu, HI 96822 United States
AU: McIntosh, K D
EM: kirk@ig.utig.utexas.edu
AF: Institute for Geophysics, University of Texas, Austin, TX 78759-8500 United States
AU: Ahmed, I
EM: ahmed@ig.utig.utexas.edu
AF: Institute for Geophysics, University of Texas, Austin, TX 78759-8500 United States
AB: The Sandino forearc basin is about 40 km wide and filled with 6 to as much as 15 km of Upper Cretaceous to Recent sediments. The sediments overly the margin wedge, consisting of the Ophiolitic Nicoya complex of Cretaceous to Early Tertiary age. In the south, the basin thins rapidly southward against ultramafic rocks of the Santa Elena peninsula of Costa Rica. Sediment thickness locally exceeds 13 km in the central and northern parts of the basin. The oldest units (Upper Cretaceous-Middle Eocene) are very thick off northern Nicaragua, with relatively thin middle to late Cenozoic deposits. In contrast, off central Nicaragua the Middle-Upper Miocene units attain great thickness (5-6 km) and the older units are thin. This pattern suggests a history of successive deepening of the basin from north to south off Nicaragua. The Nicoya complex was emplaced during Late Cretaceous to Late Eocene. Coeval uplift of the outer high and subsidence of the forearc basin are recorded in the seismic data. The variation in sediment thickness suggests an early collision of an oceanic plateau or thickened basaltic ridge in this area and likely off El Salvador as well. Basin formation may have begun with early imbrication or underplating along its seaward edge in the north during the Eocene, continuing southward in the Upper Oligocene-Lower Miocene. During the Oligocene the Corvina and Argonaut anticlines divided the depocenter of the basin into an inner, deeper part, and a western, shallower part. The anticlines are structurally fault-propagation folds, although they may have a strike-slip component of displacement. Widespread normal faulting on the outer shelf and upper slope region in the late Cenozoic and stratigraphic evidence of subsidence of this region may coincide with a period of subduction erosion combined with a steepening subduction angle. Latest Miocene uplift of the sequences along the present coastal region shifted the basin depocenter westward. Slow uplift has continued along part of the central coast into the late Pleistocene.
DE: 8015 Local crustal structure
DE: 8100 TECTONOPHYSICS
DE: 8105 Continental margins and sedimentary basins
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting