HR: 0830h
AN: T11A-06
TI: Slab Breakoff Mechanism for the Late Neogene Uplift of Honduras, Northern Central America
AU: * Rogers, R D
EM: rrogers@ig.utexas.edu
AF: University of Texas, Institute for Geophysics 4412 Spicewood Springs Road Suite 600, Austin, TX 78759-8500 United States

AB: Honduras is characterized by broad highlands with elevations of between 1 to 2.8 km extending 400 km from behind the Central America volcanic arc to the Caribbean Sea. Much of this elevated area is underlain by up to 2 km of ignimbrite and tuff deposits produced during a regional "flareup" that peaked at 15 Ma and ended by 10.5 Ma and was probably related to partial melting of continental crust beneath the area. A record of regional uplift across Honduras is recorded in deeply entrenched rivers with bedrock meanders, dissected erosion surfaces and incised bedrock channels that cut into the ignimbrites. A widespread network of incised bedrock channels and meanders has been mapped in the field, on aerial photos, and satellite images and compiled in GIS coverages. Bedrock meanders are tectonically significant because they require uplift without significant tilting to form. Bedrock channels incised into the ignimbrite date the initiation of the uplift after the peak of the ignimbrite flareup at 15 Ma. Disruption of bedrock meanders in western Honduras, related to post-10.5 Ma extension, brackets the age of uplift between 10.5 and 15 Ma. I propose regional uplift initiated in Honduras and Nicaragua between 15 and 10.5 Ma involving the breakoff of the subducted Cocos slab beneath this area and the upwelling of hotter, less dense asthenosphere into the area of slab breakoff. The presence and location of a 200-km-wide slab gap beneath northern Central America is constrained by tomographic work by van der Hilst (1990) and is projected onto maps of bedrock meanders and all dated late Neogene extrusive and intrusive units in Honduras. A possible correlation of the slab gap to geomorphic and bedrock features of Nicaragua is also presented.
UR: http://www.ig.utexas.edu/research/projects/honduras/index.html

DE: 8100 TECTONOPHYSICS
DE: 1824 Geomorphology (1625)
SC: T
MN: Fall Meeting 2000