Build‐up and depositional dynamics of an arc front volcaniclastic complex: the Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Abstract

Volcanic terrains such as magmatic arcs are thought to display the most complex surface environments on Earth. Ancient volcaniclastics are notoriously difficult to interpret as they describe the interplay between a single or several volcanoes and the environment.

Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

“…At most sites, tilting direction of the K 3 axis and the azimuth of magnetic lineation are consistent with sediment source direction as deduced from sedimentary structures. The accuracy of AMS in pyroclastic rocks could be partly supported by their closeness to their suspected source areas and through analysis of lateral facies distributions (Lenhardt et al, 2011).…”

“…Within the San Andrés Member, two depositional systems are present: a braided-river system, which dominated the deposition in the Malinalco Member, and a volcanic ring-plain system, introducing volcanic material from its source in the north (Lenhardt et al, 2011). Especially in the western part of the study area (MAL section), the roughly W-E flow direction can still Paleocurrent directional data are commonly used to interpret channel sinuosity (Ghosh, 2000;Le Roux, 2001).…”

“…Only a few lava flows and dikes are present. The Tepoztlán Formation accumulated mainly in medial to distal environments, in flank and apron settings of a volcanic ring plain, which interfingered with an axial W-E trending braided river system (Lenhardt et al, 2011). Subaerial radial ring-plains 8 usually develop around isolated volcanoes (Palmer, 1991;Palmer and Neall, 1991;Palmer et al, 1993), and consist of resedimented volcanoclastics and occasionally fluvial deposits (e.g., Cas and Wright, 1987;Cronin and Neall, 1997).…”

“…6). Lenhardt et al (2011) describe the depositional setting as a low-sinuosity channel system with high-sediment-laden debris flows and hyperconcentrated flows, originating from several volcanoes after heavy rains. The W-E trending axial braided-river system can be explained by the La Pera fault system, which has existed since pre-Miocene times (Johnson and Harrison, 1990;Garduno et al, 1993).…”

“…The studied samples of the Tepoztlán Formation comprise 5 volcanic and sedimentary lithofacies types distinguished on the basis of rock type, sedimentary and volcanic structures or textures, and grain size, consisting of lava, tuff, tuffaceous breccia, sandstone and conglomerate (Lenhardt et al, 2011).…”