New constraints on the origin of the Sierra Madre de Chiapas (south Mexico) from sediment provenance and apatite thermochronometry

Abstract

[1] The timing and source of deformation responsible for formation of the Sierra Madre de Chiapas (south Mexico) are unclear. To address this, apatite fission track and U-Th-He thermochronometry, combined with zircon U-Pb dating, were performed on bedrock and sedimentary samples of the Sierra Madre de Chiapas to discern timing of exhumation and identify sediment source areas. The U-Pb results show that Paleocene-Eocene terrigenous units outcropping at the northern section of the Sierra were mostly derived from Grenville ($1 Ga) basement whereas the internal sections of the chain yield mainly Permian to Triassic ages (circa 270-230 Ma) typical of the Chiapas massif complex. Grenville-sourced sediments are most probably sourced by the Oaxacan block or the Guichicovi complex and were deposited to the north of the Sierra in a foreland setting related to a Laramide deformation front. Other possibly source areas may be related to metasedimentary units widely documented at the south Maya block such as the Baldi unit. The apatite fission track and U-Th-He data combined with previously published results record three main stages in exhumation history: (1) slow exhumation between 35 and 25 Ma affecting mainly the Chiapas massif complex; (2) fast exhumation between 16 and 9 Ma related to the onset of major strike-slip deformation affecting both the Chiapas massif complex and Chiapas fold-and-thrust belt; and (3) a 6 to 5 Ma period of rapid cooling that affected the Chiapas fold-and-thrust belt, coincident with the landward migration of the Caribbean-North America plate boundaries. These data suggest that most of the topographic growth of the Sierra Madre de Chiapas took place in the middle to late Miocene. The new thermochronological evidence combined with stratigraphic and kinematic information suggests that the left-lateral strike-slip faults bounding the Chiapas fold-and-thrust belt to the west may have accommodated most of the displacement between the North American and Caribbean plates during the last 6-5 Ma.Citation: Witt, C., S. Brichau, and A. Carter (2012), New constraints on the origin of the Sierra Madre de Chiapas (south Mexico) from sediment provenance and apatite thermochronometry, Tectonics, 31, TC6001,

Geomorphic analysis of transient landscapes in the Sierra Madre de Chiapas and Maya Mountains (northern Central America): implications for the North American–Caribbean–Cocos plate boundary

“…The development of large alluvial valleys within the Chiapas Massif suggests that the Permian batholith and its sedimentary cover were uplifted and significantly eroded until rivers reached an almost flat base level. Indeed, Witt et al (2012a) show that the middle to late Miocene period is associated with a marked increase in erosion of the Chiapas Massif and sedimentation within the basins of the Tabasco region. The distribution of morphometric indices (Fig.…”

“…Thermochronological and stratigraphic evidence suggests two main periods of topographic growth. The first one occurred during the middle Miocene (16-10 Ma) and the latest one started during the late Miocene-Pliocene and is still ongoing (Guzmán-Speziale and Meneses-Rocha, 2000;Meneses-Rocha, 2001;Ratschbacher et al, 2009;Witt et al, 2012a). We assume that the relict landscapes of the Sierra Madre de Chiapas have developed following the middle Miocene phase of topographic growth.…”

“…Thermochronological, tectonic and stratigraphic evidence suggests that renewed exhumation and topographic growth occurred along the Chiapas region during the middle Miocene (16-10 Ma) and late Miocene-Pliocene (6-5 Ma), following a phase of rapid exhumation to upper crustal levels at ∼ 30 Ma (Ratschbacher et al, 2009;Witt et al, 2012a). The Tonalá shear zone may have accommodated significant deformation since 16 Ma, while the displacement along the transpressive Tuxtla and Malpaso faults occurred during the last 6-5 Myr and could have reached 50-70 km, involving 0.5-0.8 cm yr −1 of left-lateral motion (Meneses-Rocha, 2001;Witt et al, 2012b).…”

Elevated rates of positive selection drive the evolution of pestiferousness in the Colorado potato beetle (Leptinotarsa decemlineata, Say)

“…However, as host generalization appears to have evolved multiple times in our phylogenetic reconstruction, it seems unlikely that co-speciation with host plants is the main mechanism driving diversification in Leptinotarsa , and rather, these beetles most likely radiate onto existing hostplant diversity (Gómez-Zurita et al 2007). Alternative drivers of speciation include climatic events during the Miocene epoch (~23.03-5.33 Ma), when global temperatures became significantly warmer and drier, and geological events associated with the orogeny of the Sierra Madre de Chiapas in southern Mexico ~12-10 Ma, possibly driving speciation via allopatric isolation (Witt et al 2012). Additional sampling of Leptinotarsa and related taxa, as well as population-level sampling, will be required to test these competing hypotheses regarding plant-insect co-speciation, climate change, and geology.…”

OSLsignal resetting in young deposits determined with a pulsed photon‐stimulated luminescence (PPSL) unit

“…The sierra abruptly ends in the coastal plain of Chiapas, where the elevation is between 10 and 100 m a.s.l. (Weibel 1998;Witt et al 2011Witt et al , 2012. Rivers in this setting transport large volumes of sediment from the sierra.…”