LA-ICP-MS-based apatite fission track dating of the Todos Santos Formation sandstones from the Sierra de Chiapas (SE Mexico) and its tectonic significance

This study reports the first LA-ICP-MS-based apatite fission track age data from the Toarcian-Oxfordian Todos Santos Formation sandstones exposed in the Sierra de Chiapas (SCH), SE Mexico. Single-grain fission track ages obtained from four rock samples vary between 232 +/- 31 (1 sigma) and 40 +/- 3 (1 sigma) Ma, indicating partial resetting of detrital apatite populations by post-depositional heating during diagenesis. Decomposed data were interpreted as follows: (a) cooling of the sediment source area at 203 +/- 7 (1 sigma) and 163 +/- 3 (1 sigma) Ma, which are respectively coincident with the late Permian-Triassic thermo-tectonic event and Early-Middle Jurassic arc volcanism that affected the Chiapas Massif Complex; and (b) a post-burial cooling period (with variable cooling rates of <3 degrees C Ma(-1)) in the range of similar to 83-51Ma controlled by a Late Cretaceous-early Eocene tectonic activity, which can be correlated with the Laramide orogeny that occurred along central and northern Mexico during the same period of time (i.e. from 85-80 to 50-40Ma). The results obtained in the present study, as well as previously published data, indicate that the SCH has experienced a multi-episodic thermo-tectonic evolution with at least four main stages.