Hermosillo, Mexico
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Sulpizio R.,CNR Institute for the Dynamics of Environmental Processes | Sarocchi D.,Institute Geologia
Journal of Volcanology and Geothermal Research | Year: 2014

Pyroclastic density currents (PDCs) are mixtures of two components, namely solid particles and fluid (gas) phase. They macroscopically behave as dense, multiphase gravity currents (flowing pyroclastic mixtures of particles and gas) immersed in a less dense, almost isotropic fluid (the atmosphere). As for other natural phenomena, their study needs a multidisciplinary approach consisting of direct observations, analysis of the associated deposits, replication through laboratory experiments, and numerical simulations. This review deals with the description of the current state of the art of PDC physics, and combines analysis of data from various methodologies. All of the above-mentioned approaches have provided significant contributions to advancing the state of the art; in particular, laboratory experiments and numerical simulations deserve a special mention here for their tumultuous growth in recent years.A paragraph of the review is dedicated to the puzzling behaviour of large-scale ignimbrites, which are (fortunately) too rare to be directly observed; they cannot be easily reproduced through laboratory experiments, or investigated by means of numerical simulations.The final part is dedicated to a summary of the whole discussion, and to a comment on some perspectives for future developments of PDC studies. © 2014 .

Aguillon-Robles A.,Institute Geologia | Tristan-Gonzalez M.,Institute Geologia | De Jesus Aguirre-Diaz G.,National Autonomous University of Mexico | Lopez-Doncel R.A.,Institute Geologia | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2014

The San Luis Potosí Volcanic Field (SLPVF) of central Mexico includes volcanic sequences of felsic, intermediate and basic compositions that were erupted as discrete episodes from the Eocene to the Pleistocene. Volcanism was dominated by widespread and voluminous rhyolitic ignimbrites of the mid-Tertiary Ignimbrite Flare-up. However, the complete volcanic history must consider basaltic and andesitic Eocene-Pleistocene volcanic successions that provide key evidence for understanding the geochemical evolution of the volcanism in the SLPVF during this time span. Five sequences are recognized according to their geochemical characteristics, each comprising a volcano-tectonic episode. The first episode comprises basaltic andesites and andesites erupted during three intervals, 45-42. Ma, 36-31. Ma, and 31-30. Ma. The oldest was derived from subduction magmatism, whereas the youngest has an intra-plate magmatic signature and this represents the transition from the end of a long lasting subduction regime of the Farallon plate to the initiation of intra-plate continental extension in the North American plate. The second episode, at 29.5-28. Ma, comprises a bimodal succession of high-silica rhyolites and alkaline basalts (hawaiites) that are interpreted as magmatism generated in an intra-plate continental extension regime during the Basin and Range faulting. The third episode, at 21. Ma, is characterized by trachybasalts and trachyandesites that represent mantle basaltic melts that were contaminated through assimilation of the lower crust during advanced stage of intra-plate extension that started at Oligocene. The fourth episode includes 12. Ma alkaline basalts and andesites that were erupted from fissures. These mantle derived magmas evolved to andesites by crustal anatexis and crystal fractionation within a continued, extensional, intra-plate regime. Lastly, the fifth episode comprises 5.0 to 0.6. Ma alkaline basalts (basanites) containing mantle xenoliths, that were erupted from maars and tuff cones, which are the youngest manifestations of mantle-derived intra-plate extensional events. Based upon this volcanic record, the last subduction manifestations of the extinct Farallon plate occurred at about 42. Ma, this was followed by a transition to intra-plate magmatism between 42 and 31. Ma, and an extensional, intra-plate tectonic setting from 31. Ma to almost Present. © 2014 Elsevier B.V.

Villasenor A.B.,Institute Geologia | Oloriz F.,University of Granada | Lopez Palomino I.,Servicio Geologico Mexicano | Lopez-Caballero I.,Sede Institute Geologia
Revue de Paleobiologie | Year: 2012

Ten years after the publication of "Recent advances in Upper Jurassic (Kimmeridgian-Tithonian) ammonite biostratigraphy of north-central Mexico, based on recently collected ammonite assemblages", a working program based on bed-by-bed sampling of upper Jurassic sections in Mexico has allowed to improve information about known and new outcrops in northeastern, central-eastern and south-eastern Mexico. The present contribution provides an updating of the obtained information, a part of which has been published elsewhere. Of special relevance are new data concerning Oxfordian and latest Kimmeridgian/earliest Tithonian ammonites from central-east and south-eastern Mexico, which are considered as preliminar information of prime importance for correlation. A re-evaluation of registered ammonite assemblages is made in terms of faunal - ammonite - horizons of three orders of relevance for biostratigraphic correlation in Mexico. They integrate within the ammonite assemblages formally proposed previously, and their biochronostratigraphic meaning is only tentatively approached due to the incidence of endemism.

Omana L.,Institute Geologia | Doncel R.L.,Autonomous University of San Luis Potosi | Torres J.R.,Autonomous University of San Luis Potosi | Alencaster G.,Institute Geologia
Micropaleontology | Year: 2012

Lithologic and foraminiferal analysis from the western part of the Valles-San Luis Potosí platform reflect a sea-level rise suggesting that the platform was drowned at the Cenomanian-Turonian boundary interval. Benthic and planktic foraminiferal content of the succession was identified to establish the transition from the shallow-water carbonate sedimentation with abundant larger benthic foraminifera, algae, rudists and other molluscs, corals, echinoderms, worms changing to hemipelagic-pelagic sediments containing calcispheres and opportunistic foraminifers (r-strategists), such as whitenellids, hedbergellids, heterohelicids and elongated chambered forms, as well as radiolarians. The El Abra Limestone is dated as the middle-late Cenomanian age (Pseudolituonella reicheliAssemblage Zone) and was deposited on a warm shallow-marine rimmed platform. Peloidal-bioclastic packstone-grainstone is the dominant texture of these rocks. Lithological variations determined by the high detrital influx were followed by a major transgression when wackestone and marly limestone of the lower part of the Soyatal Formation were deposited. The transition to deeper open marine environments is dated as latest Cenomanian/earliest Turonian represented by the Whiteinella archaeocretacea Partial Taxon Range Zone and coincides with a global sea-level rise and the Oceanic Anoxic Event 2 (OAE 2). Deeper overlying deposits of the Helvetoglobotruncana helvetica Total Range Zone (early/middle Turonian) are characterized in the study area by the occurrence of the keeled forms (k strategists). The Cenomanian/Turonian boundary is placed within the Whiteinella archaeocretacea Partial Range Zone in absence of ammonite markers. When theValles-San Luis Potosí platformwas flooded, the carbonate factorywas stressed due to the trophic resource modifications. Production of a larger amount of nutrients led to the extinction of the k-strategist benthic foraminifera; only small benthic foraminifera survived for a short period of time in the newly established mesotrophic conditions. High productivity continued and in the eutrophic episode the calcispheres, r-opportunists, intermediate taxa and the planktic foraminifera with elongate chambers proliferated. Later, complete drowning enabled the recovery of oligotrophic conditions with the occurrence of k-strategist keeled planktic taxa.

Sulpizio R.,CIRISIVU | Capra L.,National Autonomous University of Mexico | Sarocchi D.,Institute Geologia | Saucedo R.,Institute Geologia | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2010

Maps of areas potentially affected by block-and-ash flows and associated ash clouds are here presented for the Volcán de Colima. TITAN2D 2.0.1 code has been used to simulate block-and-ash flows using as an input volume that of the actual summit dome (assessed at 2×106m3), while the Energy Cone model has been used to delimit the possible inundated area from associated ash clouds. Both Merapi- and Soufriere-type block-and-ash flows were generated using different basal friction angles and maintaining fixed the volume and the internal friction angle. The setting of the input parameters takes into account some flow characteristics, such as the stepwise aggradation of different pulses that piled up to form the total thickness of the block-and-ash flow deposits. The outputs of the computational routines are reported as two maps describing the total thickness of the final deposits. They predict that thick deposits will engulf the ravines descending from the main cone to the west, south and southeast, with expected maximum runouts between 4.5 and 7km. The associated ash clouds have slightly longer runouts, and the model predicts they will inundate some higher grounds that are not affected by the concentrate underflows. The presented maps represent useful tools for managing the current block-and-ash flow hazard at Volcán de Colima. © 2010 Elsevier B.V.

Charpentier I.,French National Center for Scientific Research | Sarocchi D.,Institute Geologia | Rodriguez Sedano L.A.,National Autonomous University of Mexico
Computers and Geosciences | Year: 2013

This paper presents a modular Matlab tool, namely MORPHEO, devoted to the study of particle morphology by Fourier analysis. A benchmark made of four sample images with different features (digitized coins, a pebble chart, gears, digitized volcanic clasts) is then proposed to assess the abilities of the software. Attention is brought to the Weibull distribution introduced to enhance fine variations of particle morphology. Finally, as an example, samples pertaining to a lahar deposit located in La Lumbre ravine (Colima Volcano, Mexico) are analysed. MORPHEO and the benchmark are freely available for research purposes. © 2012 Elsevier Ltd.

Berriasian-Aptian stratigraphic sections of the Sabinas Basin, northeast Mexico, show three major unconformities as second order sequence boundaries. Every sequence includes transgressive-regressive tracts and a maximum flooding zone. From the Chihuahua Basin to the Tampico Basin there are transgressive-regressive tracts placed at the same age and stratigraphic level, which are correlative to the Sabinas sections. The previous sequence boundaries may have a subordinate tectonic component, but sequence analysis indicates that these sequences are due to variations mostly linked to eustatic changes in sea level globally, as mentioned by other authors. © 2011 Sociedad Geológica Mexicana.

de Antunano S.E.,197 Slade Lane | de Antunano S.E.,Institute Geologia
Boletin de la Sociedad Geologica Mexicana | Year: 2011

The Burgos Basin is located at the Coastal Plain of the Gulf of Mexico. It consists of more than 5000 m of siliciclastic Cenozoic rocks and more than 3000 m of Mesozoic carbonate, evaporite and siliciclastic rocks. The basin contains stratigraphic sequences with transgressive and regressive cycles with unconformities limiting several of the sequences. This basin experienced several superimposed tectonic events. The complex basement contains both metamorphic and igneous rocks, affected by rifting during the opening of the Gulf of Mexico. As a result of crustal subsidence, marine pre-tectonic and syntectonic sediments accumulated from Late Jurassic to Eocene. The Laramide episode is represented by foreland deposits, deeply erosive surfaces, and broad folds. An upper detachment level, with syndepositional listric faults and roll-over structures, denotes tectonic extension during the Paleocene and Eocene. The post-tectonic stage is associated to basement uplift during the Oligocene, deep detachment on Jurassic evaporites, decoupling of sedimentary cover link to extension faults, and a main unconformity at 30 Ma. The early phase of the Perdido Fold Belt occurred at this stage. This event is linked to cortical uplift and may be related to the emplacement of the East Alkaline Magmatic Arc, during the Oligocene. Finally, from late Oligocene to Neogene thick siliciclastic prograding sequences accumulated towards the Gulf of Mexico. The late phase of deformation consists of growth faults associated to shale and Jurassic salt diapirs, and a late deformation of the Perdido Fold Belt. In this basin there have been discovered more than 220 onshore gas fields in Cenozoic and Mesozoic rocks, with a cumulative production of over 8 × 1012 ft3 of dry gas and subordinate condensate in over 60 years of exploitation. The next challenge will be to discover new productive plays in stratigraphic traps, Mesozoic structures and oil and gas reservoirs offshore. © 2011 Sociedad Geológica Mexicana.

Giambiagi L.,CONICET | Mescua J.,CONICET | Folguera A.,Institute Geologia | Martinez A.,National University of San Luis
Revista de la Asociacion Geologica Argentina | Year: 2010

The structure of the southern sector of the Precordillera is the result of different deformational events: Eopaleozoic, Neopaleozoic, Permian- Triassic and Cenozoic, each one with particular strike, vergence and style. Many early and late Paleozoic structures have been reactivated during the subsequent tectonic events. The kinematic analysis of Eopaleozoic structures allows us to distinguish between two deformational events with particular kinematic characteristics. The first event, D1, shows an E-W maximum shortening direction and westward vergence. The second event, D2, shows a NW to WNW maximum shortening direction and double vergence. Two models explain this kinematic variation; whether the two events were separated in time and respond to different tectonic events, or they are related to a transpressive event with rotation of the shortening direction through time. The late Paleozoic deformation was characterized by the generation of a thin-skinned fold and thrust belt in the eastern sector and a thick-skinned one in the western sector with reactivation of Eopaleozoic structures. The kinematic analysis indicates a NW-SE shortening direction and double vergence. During the extensional period, from Late Permian to Middle Triassic, the region had a transtensional deformation produced by a NE extensional direction and the reactivation of a NNOoriented preexisting weakness zones. The pre-Andean structures were reactivated during the Andean orogeny, generating a thick-skinned fold and thrust belt with double vergence.

Sarocchi D.,Institute Geologia | Sulpizio R.,University of Bari | Macias J.L.,National Autonomous University of Mexico | Saucedo R.,Institute Geologia
Journal of Volcanology and Geothermal Research | Year: 2011

On July 17 1999, a strong explosion occurred at Colima Volcano (Mexico) that produced a 10km high eruptive column. The partial column collapse originated a block-and-ash flow (BAF) that flowed to the south, along the San Antonio and Montegrande ravines, travelling 3.3km from the volcano summit. The flow filled the ravines with a volume estimated at 7.9×105m3. The erosion of these deposits occurred between 1999 and 2002 (time of sampling), providing excellent longitudinal outcrops that allowed their detailed textural study. The study was carried out by means of quantitative textural analysis: (1) Rosiwal intersections, for carrying out vertical granulometric profiles; (2) total grain-size analysis, from -11 to +9 Φ; and (3) Fourier and fractal analysis of the particle morphology. Grain size and morphometric parameters obtained with these methods were used to identify vertical and longitudinal variation patterns in the BAF deposit. The grain size variations allowed to infer the main particle segregation mechanisms that acted during transport and deposition of the studied BAFs. The two methods used for studying the particle shape morphologies yielded results with different accuracy and reliability. In particular, fractal analyses have been found to be the most effective in describing the particle support mechanisms that acted during transport and deposition of the studied BAFs.The results highlight the importance of the information obtained by means of these techniques, and provide new insights in transportation and deposition mechanisms of BAFs. © 2011 Elsevier B.V.

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