HR: 1330h
AN: T52C-0289    [PDF]
TI: Tectonic Structure of the Middle America Pacific Margin and Incoming Cocos Plate From Costa Rica to Guatemala
AU: Ranero, C R
EM: cranero@geomar.de
AF: GEOMAR and SFB574, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: * Weinrebe, W
EM: wweinreb@geomar.de
AF: GEOMAR and SFB574, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Grevemeyer, I
EM: igrevemeyer@geomar.de
AF: GEOMAR and SFB574, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Phipps Morgan, J
EM: jmorgan@geomar.de
AF: GEOMAR and SFB574, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Vannucchi, P
EM: paola@geo.unifi.it
AF: Universita di Firenze, Via la Pira, 4, Florence, 50121 Italy
AU: von Huene, R
EM: rhuene@geomar.de
AF: GEOMAR and SFB574, Wischhofstrasse 1-3, Kiel, 24148 Germany
AB: A new multibeam bathymetry and magnetic survey with R/V SONNE in summer 2003 has mapped the continental margin and incoming plate of NW Nicaragua, El Salvador and Guatemala, extending existing coverage from offshore Costa Rica and part of Nicaragua to a full coverage map of about 1200 km long by 100 km wide area along the plate boundary. The incoming plate along Nicaragua, El Salvador and Guatemala is of similar age and was formed at superfast spreading rates; however, its morphology changes drastically along strike. The seafloor-spreading inherited morphology is very smooth along Nicaragua, but with ridges up to 800 m high in Guatemala, with a transition across El Salvador. The development and dimensions of the dominant inherited fabric seems to be related to discontinuities at the paleospreading center. A series of troughs oblique to the main fabric may indicate the location of pseudofaults and correspond to areas where the seafloor fabric is most prominent. Bending of the oceanic plate into the trench reactivates the inherited fabric forming a well pervasive faulting system along the oceanic trench slope. The continental slope displays three morphotectonic units that roughly correspond to the upper, middle and lower slope, although the across slope width of each unit is fairly variable. Small canyons and gullies that form at the sudden dip change across the shelf break carve the upper slope. The canyons coalesce and become shallower as the dip decreases downslope. Locally some large canyons continue into the slope toe. The middle slope is a rough terrain variable in width and dip sculptured by pervasive normal faulting and locally by mass wasting processes. The lower slope is formed by en echelon terraces striking similar to the rough terrain of the incoming plate and mimicking the half graben morphology of the underthusting plate. The three morphotectonic slope domains represent differences in tectonic activity, with more stable upper slope, a middle slope dominated by tectonic extension and the thin, highly fractured upper plate of the lower slope riffling over the incoming plate topography. The trench axis is largely empty, with local turbidite ponds at the mouth of a few large canyons transecting the entire slope.
DE: 3045 Seafloor morphology and bottom photography
DE: 8100 TECTONOPHYSICS
DE: 8105 Continental margins and sedimentary basins
DE: 8150 Plate boundary--general (3040)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting