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Gravimetric analysis of the rifts and volcanic fields of the Jalisco block, Mexico

2020; Elsevier BV; Volume: 791; Linguagem: Inglês

10.1016/j.tecto.2020.228577

1879-3266

Miguel Ángel Martínez Camacho, Román Álvarez,

Geological and Geochemical Analysis

The gravity map of the complete Jalisco Block (JB) is obtained from satellite-derived measurements at a resolution of ~1 km separation, including the offshore region up to the Middle America Trench (MAT). Tepic-Zacoalco (TZ) and Colima delimiting rifts of the JB are identified as gravimetric minima. The NW limit of the block appears also as a rifted zone, with a gravity minimum connecting Bahia de Banderas with the TZ rift, defining a new triple point: the Compostela Triple Point (rift-rift-rift) that together with the Guadalajara Triple Point determine the north boundary of the Jalisco Block. The largest negative gravity anomalies are observed associated with the Central Jalisco Volcanic Lineament (CJVL) and Bahía de Banderas; they appear to be connected since they are only separated by a small positive anomaly east of Bahía de Banderas. The CJVL is parallel to the Middle America Trench, exhibiting a discontinuous alignment of Quaternary volcanism from the Colima Volcanic Complex to the northwestern rifted limit of the Jalisco Block. Ameca and Santiago rivers flow parallel to each other in a northwesterly direction for 100 km, then Santiago river changes course to continue 64 km in a north-northwesterly direction up to Aguamilpa dam. Ameca river should follow the same direction; instead, it abruptly changes its course to a southwesterly direction to discharge in Bahía de Banderas. The drastic course deviation is attributed to the intersection of Ameca river causeway with the Bahía de Banderas-Compostela rift, proposed in this study to be the northwestern limit of the Jalisco Block.