Carbonate detritus and mylonite zones in Guerrero, Mexico and northern Honduras: new evidence for detachment of the Chortis block from southern Mexico

Brecciated lower Cretaceous carbonates on a collapsed margin in Guerrero add support to the growing evidence for the Chortis block originating from, and later detaching from, southern Mexico. Fault blocks with over 2000 m of breccia have been measured, suggesting breakup of a carbonate platform due first to magmatic uplift and later due to transcurrent faulting during detachment. There is less breccia on the Chortis block; however, magmatism may have been responsible for extensive block faulting which resulted in thick sections of well rounded limestone conglomerate that have been observed in Honduras. te scars may be evidence of basement rifting and are the basis for dividing the Xolapa complex, created by early Paleogene magmatism, into three sub-blocks. At about the same time Chortis may also have been broken into three sub-blocks by sinistral forces. A tectonic history is proposed that is based on published work by others but supported by data presented in this paper.