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Hermosillo, Mexico

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 .

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.

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.

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.

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