Structural geology and geochronology of the Comondú Group in the Tembabichi area, Baja California Sur, México

Abstract

This study provides a geological map and regional interpretation of an area spanning E-W across the southern Baja California peninsula, Mexico. Characterizing the kinematics and timing of deformation within the Comondú Group (Oligocene–Miocene) is crucial to understand the evolution of the Gulf of California rift. Structural evidence indicates that the Lower Comondú volcanic and sedimentary sequence (dated ∼29–19 Ma) was deposited in a sedimentary basin bounded by regional west-dipping normal faults, reflecting the progressive development of a broad extensional zone. We document NW to NE-trending, SW to NW-dipping normal faults, along with mafic and pyroclastic dykes dated between 18 and 15 Ma that share similar kinematic characteristics. Our findings suggest that these dykes were emplaced along pre-existing normal faults affecting the Lower to Middle Comondú Group. The geochronological and structural data presented on the main map provide new insights for deciphering the complex geological evolution of this region.

Keywords

• Comondú Group
• Gulf of California rift
• 40Ar/39Ar dating
• West dipping normal faults
• mafic dykes
• pyroclastic dykes