Volcano-sedimentary processes at Las Derrumbadas rhyolitic twin domes, Serdán-Oriental basin, Eastern Trans-Mexican Volcanic Belt

The eruption of the ∼10 km3 rhyolitic Las Derrumbadas twin domes about 2000 yrs ago has generated a wide range of volcano-sedimentary deposits in the Serdán-Oriental lacustrine basin, Trans-Mexican Volcanic Belt. Some of these deposits have been quarried, creating excellent exposures. In this paper we describe the domes and related products and interpret their mode of formation, reconstructing the main phases of the eruption as well as syn-and-post eruptive erosional processes. After an initial phreatomagmatic phase that built a tuff ring, the domes grew as an upheaved plug lifting a thick sedimentary pile from the basin floor. During uplift, the domes collapsed repeatedly to form a first-generation of hetero-lithologic hummocky debris avalanche deposits. Subsequent dome growth produced a thick talus and pyroclastic density currents. Later, the hydrothermally-altered over-steepened dome peaks fell to generate 2nd generation, mono-lithologic avalanches. Subsequently, small domes grew in the collapse scars. From the end of the main eruptive episode onwards, heavy rains remobilized parts of the dome carapaces and talus, depositing lahar aprons. Las Derrumbadas domes are still an important source of sediments in the basin, and ongoing mass-wasting processes are associated with hazards that should be assessed, given their potential impact on nearby populations.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5752296

The Historical Seismicity of the Puebla-Tlaxcala Region (Trans-Mexican Volcanic Belt) during Early Novohispanic Times (A.D. 1542–1740) and the Structure of the Tlaxcala-Huamantla Half-Graben

This article documents earthquake intensity observations during early novohispanic times (A.D. 1542–1740) in the Puebla-Tlaxcala region (central Mexico), mostly based on Nahuatl-language historical annals and chronicles, and includes (as a supplement) a descriptive earthquake catalog for this period. Although it is difficult to assign intensities from fragmentary accounts, the largest shocks (A.D. 1582 and 1711) caused damage through the entire region. Earthquake ground shaking in the study area, located within the active volcanic arc crossing central Mexico, can result from intraslab normal faulting in the subducted Cocos plate, subduction interface thrust earthquakes, motion on the faults of the intra-arc Tlaxcala-Huamantla half-graben, as well as extension accommodated through magmatic injection. Most of the historical sources describe earthquakes felt only locally and sometimes report prolonged sequences of shocks, which is indicative of magmatic dike-induced earthquakes or else resulted from motion on the faults of the Tlaxcala-Huamantla half-graben. This structure, ∼70 km long and 15–20 km wide, is the only major tectonic depression in the eastern part of the trans-Mexican volcanic belt. It is filled by a volcano-sedimentary sequence, up to 400 m thick, of unknown but likely Pliocene age. The half-graben is bound in the north by an east–west-striking and south-dipping normal fault system, which is morphologically most pronounced near the town of Tlaxcala where the footwall uplift reaches a maximum of 350 m. The fault array is likely to be active; it vertically displaces Quaternary Totolqueme volcano.

Canine Silica Urolithiasis in Mexico, Associated with the Concentration of Dissolved Silica in Tap Water

Silica urolithiasis is infrequent in dogs, but in Mexico represents 12.9%. Our hypothesis is the consumption of high amounts of silicates in the diet, especially that dissolved in tap water. The objective of this study was to determine the concentrations of silica in the tap water in different geographical areas and their relationship with cases of silicate urolithiasis in dogs. From 179 cases of silicate urolithiasis, 98.9% were from dogs within a geographic area called the Trans-Mexican Volcanic Belt, which represents a cross shaft to the center of the country. Silica concentrations in tap water ranged between 3 and 76 mg/L, with a range of 27 to 76 mg/L, a mean of 49.9 ± 12 mg/L within the Trans-Mexican Volcanic Belt, and a concentration from 3 to 30 mg/L, with a mean of 16.4 ± 7 mg/L outside this area; these were significantly different ( p < 0.001 ). These findings demonstrate that there is a geographic risk factor for silicate urolithiasis in urolith-forming dogs, related to the consumption of tap water with a high concentration of silica. Further studies are necessary to identify this same pathophysiological association in other species.