The Middle America Trench in the Geological Framework of Central America

The tectonic framework of the Middle America Trench is composite. In its northern part, the Trench runs along the North American continent (at the least, along Mexico up to the Guatemala Transverse Zone; at the most, up to the Honduras Platform). In this part the Trench is not related to the tectonic features of Mexico, which it cuts very obliquely, and is thus a recent neotectonic feature. In its southern part, the Isthmus of Central America is a tectonic edifice (with a strike like that of the Trench) supporting a huge Tertiary volcanic cover; in this part, the Trench could have originated from an ancient subduction zone involving Mesozoic oceanic sediments and crust. Along the Guatemala Transverse Zone the following events took place: at the end of the Cretaceous, a big overthrust of Central American-Caribbean ophiolitic facies occurred towards the north, at the termination of the North American continent; and during the Pliocene to Quaternary there was a strong sinistral strike slip motion along the Quaternary there was a strong sinistral strike slip motion along the Polochic-Motagua Fault Zone. One should note that the division of the Middle America Trench by the Tehuantepec Ridge does not correspond to the tectonic or the neotectonic division of Central America along the Guatemala Transverse Zone or the PolochicMotagua Fault Zone. Presently the Middle America Trench is a neotectonic feature. Its northern part, the Acapulco Trench, could have been initiated by a large sinistral strike slip motion giving to the Honduras Platform an offset of about 800 km with regard to the Oaxaca Platform and cutting the Mexican structure off. Whereas its southern part, the Guatemala Trench, could have resulted from a long-lived subduction zone, perhaps related to the Franciscan subduction zone of North America. The occurrence of Upper Jurassic-Cretaceous-Tertiary oceanic sediments in the slope of the Guatemala Trench, as well as in the Nicoya Complex of Costa Rica, is a strong argument against the generally accepted idea of a Pacific origin for the Caribbean Plate, which can be better understood as a part of the Tethys.

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