CENOZOIC ROTATION OF THE YUCATAN (MAYA) BLOCK ALONG THE ORIZABA FAULT ZONE OF SOUTHERN MEXICO AND THE FAULTS OF CENTRAL AMERICA

Yucatan (Maya)has been an independent block since early Cenozoic when counter-clockwise rotation began that continues today. It is bounded in Mexico by the Orizaba fault zone (OFZ), which begins near the Gulf of Mexico at the Santa Ana massif, runs along the western Isthmus of Tehuantepec, crosses the northern Gulf of Tehuantepec W of the Chiapas massif, and connects with the major faults of Guatemala and the Cayman trough. Faults of Guatemala and adjacent Honduras are boundaries to wedges whose eastward rotation has been away from the Cuicateco terrane of Oaxaca, Mexico.

Dextral slip of about 340 km across the OFZ is measured by offset of Laramide structures and Mesozoic and Tertiary contacts of the northern Chiapas massif from those in the fold and thrust belt of the Sierra Madre Oriental. Reversing the Cenozoic counter-clockwise rotation and simultaneously restoring previously-known sinistral offset across the Polochic fault of 130 km, moves the westernmost part of the tapered block between the Polochic and Jocotan faults (Chuacus-Tambor block) of Guatemala to a position between the Yucatan and Guerrero blocks about 160 km NW of the Pacific coast. Very little offset occurred across the Motagua fault zone. The northernmost part of the Chiapas massif is moved NW across the Isthmus to near the Santa Ana uplift near the Gulf of Mexico.

Ophiolites, granitoids, metasedimentary rocks and volcaniclastics related to Cretaceous arc magmatism found in the Cuicateco terrane of Oaxaca and Tambor of Guatemala are juxtaposed with this restoration model. Obduction during strike-slip movement may account for wider distribution of ophiolites of Guatemala, which were obducted during strike-slip movement.

The eastern Veracruz basin opened during rotation of the Yucatan block. Sinistral offset across the Chiapas Strike-Slip fault zone may reflect partial decoupling from the rest of the Yucatan block. The western basin (Cordoba platform) was dropped downward at an early stage of rotation.