Papers by Renata Nela Tomezzoli
Frontiers in Earth Science, Nov 7, 2023
Geological evidence indicates that the deformation along the southwest Gondwana margin began duri... more Geological evidence indicates that the deformation along the southwest Gondwana margin began during the Middle-to-Late Devonian (the Acadian-Cháñica orogenic phase in Argentina). It has been interpreted that this deformation occurred as a consequence of the collision of Chilenia from the west and Patagonia from the south-southwest with Gondwana. As both Chilenia and Patagonia collided at the same time, in this study, we proposed that these continental blocks conform to the same allochthonous drift terrain, named here as CHIPA. The geological evolution of this margin is still under debate. Field work, paleomagnetic studies, and anisotropy of magnetic susceptibility (AMS) studies were integrated from different localities along this paleomargin in Argentina. In Permian rocks, all the geological indicators show a clear regional NW-SE elongation signature and NE-SW shortening direction. The middle Devonian to Permian patterns are more complex as the result of stress interference and the overlapping of orogenic activities with different intensities and ages. The deformation that started as the product of the CHIPA collision with Gondwana during the Middle Devonian continued through the Permian (the Hercinian-San Rafael orogenic phase in Argentina) as post-collisional compressive deformation, consequence of the paleogeographic reorganization of Gondwana and Laurentia, which moved toward the Equator from the south and the north, respectively, to form the Pangea supercontinent during the Triassic.
5th International Congress of the Brazilian Geophysical Society, 1997
Given the already documented bias in the determination of intersecting remagnetization great circ... more Given the already documented bias in the determination of intersecting remagnetization great circles as a function of the parallelism of the circles, resulting in an elongated bias in that direction, we found that rotational symmetry assumptions around the intersection would seem to be insufficient. In this contribution, we address the intersection and its inherent bias by doing bootstrap. Repeated calculations explore possible outcomes numerically; elongated distributions of the bootstrapped intersections are regarded as biased. The method calculates a more realistic confidence region based on the empirical distribution of the bootstrapped intersections. A preliminary version of the program implementing the method described here is available from L. Gallo on request.
Marine and Petroleum Geology, 2022
Journal of Palaeogeography
Apparent polar wander path of Gondwana for the Late Paleozoic proposed by <i>Tomezzoli</... more Apparent polar wander path of Gondwana for the Late Paleozoic proposed by <i>Tomezzoli</i> [2009] and<i> Gallo et al.</i> [2017] with the respective ASM patterns (with bedding correction). The abrupt changes in the trajectory of the curve is accompanied by events of greater deformation, evidenced by geological changes in the outcrops, micro-tectonic characteristics, types of magnetizations and different AMS signatures. The shortening direction indicates that the maximum stress along this part of the Gondwana boundary come from the southwest and stay stable during the Lower Carboniferous up to the Permian. These paleogeographic changes associated with that deformation are registered in the cusp that presents the apparent polar wander path of Gondwana during that period. The deformation propagated diachronous eastwards to the foreland, displaying signs first of a decrease and a subsequent pick up of intensity to decays again, suggesting cycles of higher and low...
(a) Evolution in the ellipsoids according the shape parameter (T) and the anisotropy degree (P<... more (a) Evolution in the ellipsoids according the shape parameter (T) and the anisotropy degree (P<sub>j</sub>), in the Arroyo Atravesado (green dots; this work) and in other localities of Tunas Formation (blue dots) [<i>Arzadún et al.</i>, 2016]. GC: González Chavez (top of the sequence), LS: La Susana, LM: Las Mostazas, 2M: 2 de Mayo, AP: Arroyo Paretas, R76: Ruta 76, SC: San Carlos, GA: Golpe de Agua. Sauce Grande Formation is the base of the sequence and GC locality is the top). (b) Simplified curve that shows the evolution of the deformation. SD in red: spasmodic (stronger) moments of the deformation. The arrows indicate the increase of the shortening, from the top to the base, as the deformation decrease at the top of the sequence. Comparison with conceptual models [<i>Saint-Bezar et al.</i>, 2002; <i>Parés and van der Pluijm</i>, 2003; <i>Weil and Yonkee</i>, 2009] showed in (c). There are changes in the shape of the ellipsoids, from triaxial to prolate and oblate indicating a migration from tectonic to sedimentary fabric in all the cases.
Nature-Scientific Reports, Aug 16, 2023
At the east of the Ventana Ranges, in Buenos Aires province, Argentina, outcrops the Carbonifer... more At the east of the Ventana Ranges, in Buenos Aires province, Argentina, outcrops the Carboniferous-Permian Pillahuincó Group. In the Arroyo Atravesado section, we carried out an AMS study that displays ellipsoids with constant Kmax axes trending NW-SE, parallel to the fold axes. The Kmin axes are orientated in the NE-SW quadrants, and they oscillate from horizontal (base of the sequence-western) to vertical (top of the sequence-eastern) positions, showing a change from tectonic to almost sedimentary fabric reflecting differences in the shortening. This is in concordance with the type and direction of foliation measured in petrographic thin sections which is continuous and penetrative in the western and older formations and spaced and less developed in the eastern and younger units. We integrated this study with previous Tunas Formation results (Permian of the Pillahuincó Group) displaying similar changes in the AMS pattern (tectonic to sedimentary fabric), as well as other characteristics such as the paleo-environment and sharp curvature in the apparent polar wander path of Gondwana, that mark a new threshold in the evolution of the basin. Those changes along the Pillahuinco deposition indicate two different spasms in the tectonic deformation, according to the ages of the rocks. This Carboniferous-Permian deformation is locally assigned to the San Rafael (Hercinian) orogenic phase, interpreted as the result of rearrangements of the microplates that collided previously with the margins of Gondwana, and latitudinal movements of Gondwana toward north and of Laurentia toward south to reach the Pangea configuration during the Triassic.
5th International Congress of the Brazilian Geophysical Society, 1997
AMS data of the different localities of the Tunas Formation situated in Sierra de las Tunas, Sier... more AMS data of the different localities of the Tunas Formation situated in Sierra de las Tunas, Sierra de Pillahuincó and Claromecó Basin, from de base to the top: AMS ellipsoids with structural correction, with horizontal bedding planes, and ratio between the degree of anisotropy (P<sub>j</sub>) and the shape parameter (T), with the average values in red.
Revista de la Asociación Geológica Argentina, May 24, 2021
International Journal of Earth Sciences, 2009
Plane strain tests were performed on seven kaolinite blocks, each of which developed shear bands.... more Plane strain tests were performed on seven kaolinite blocks, each of which developed shear bands. Anisotropy of magnetic susceptibility (AMS) analysis of the kaolinite reveals a threshold degree of magnetic anisotropy (P 0) exceeding which shear bands develop. Since P 0 is a strain-intensity gauge and soils are known to develop shear bands prior to landsliding, it is concluded that soil in every landslide-prone region must have its unique threshold P 0 exceeding which it develops shear bands before failing. Therefore, AMS monitoring of soil in landslide prone regions is proposed as a potential tool in the management of natural hazard zones.
Journal of South American Earth Sciences, 2021
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
La Formación Lolén, de edad devónica, aflora en el ámbito geológico de las Sierras Australes de l... more La Formación Lolén, de edad devónica, aflora en el ámbito geológico de las Sierras Australes de la provincia de Buenos Aires. La evolución geológica de esta región sigue siendo en la actualidad motivo de debate. En este trabajo se presentan los resultados de anisotropía de susceptibilidad magnética y paleomagnetismo. Los muestreos se realizaron dentro de la estancia Las Acacias cuya posición geográfica es 38° 04,2’ latitud Sur y 61° 52,76’ longitud Oeste. En la Formación Lolén fue posible aislar una magnetización preliminar postectónica de edad pérmica. Esto pone en evidencia la apertura del sistema magnético con posterioridad a su plegamiento. La fábrica magnética es de tipo oblada de origen tectónico e indica una dirección de máxima compresión SO-NE que está relacionada con los planos de clivaje que cortan a las estructuras de plegamiento previas. El hecho de que estas rocas sean portadoras de una magnetización postectónica pérmica, así como de una fábrica magnética tectónica, est...
Outcrop data for each formation of the Arroyo Atravesado locality of 103 specimens and its anisot... more Outcrop data for each formation of the Arroyo Atravesado locality of 103 specimens and its anisotropy of magnetic susceptibility parameters. B. Plane: bedding strike (0º-360º) and dip (90° clockwise, from given strike, 0º-90º). Cleavage: direction (0º-360º) and dip (90° clockwise, from given strike, 0º-90º). S<sub>0</sub> and S<sub>1</sub> foliations measured in thin sections (0°-360°). K<i><sub>max</sub></i>: average orientation of the maximum axe of AMS; K<sub>m</sub> = (K<sub>max</sub>+K<sub>int</sub>+K<sub>min</sub>)/3: average susceptibility volume in SI units; P<sub>j</sub> av: average anisotropy degree (P = K<sub>max</sub>/K<sub>min</sub>: anisotropy degree according to <i>Nagata</i>, 1961); T: average shape parameter of Jelinek (<i>Jelinek</i>, 1981); L = K<sub>max</sub>/K<sub>int</sub>: Average li...
Apparent polar wander path of Gondwana for the Late Paleozoic proposed by <i>Tomezzoli</... more Apparent polar wander path of Gondwana for the Late Paleozoic proposed by <i>Tomezzoli</i> [2009] and<i> Gallo et al.</i> [2017] with the respective ASM patterns (with bedding correction). The abrupt changes in the trajectory of the curve is accompanied by events of greater deformation, evidenced by geological changes in the outcrops, micro-tectonic characteristics, types of magnetizations and different AMS signatures. The shortening direction indicates that the maximum stress along this part of the Gondwana boundary come from the southwest and stay stable during the Lower Carboniferous up to the Permian. These paleogeographic changes associated with that deformation are registered in the cusp that presents the apparent polar wander path of Gondwana during that period. The deformation propagated diachronous eastwards to the foreland, displaying signs first of a decrease and a subsequent pick up of intensity to decays again, suggesting cycles of higher and low...
(a) Evolution in the ellipsoids according the shape parameter (T) and the anisotropy degree (P<... more (a) Evolution in the ellipsoids according the shape parameter (T) and the anisotropy degree (P<sub>j</sub>), in the Arroyo Atravesado (green dots; this work) and in other localities of Tunas Formation (blue dots) [<i>Arzadún et al.</i>, 2016]. GC: González Chavez (top of the sequence), LS: La Susana, LM: Las Mostazas, 2M: 2 de Mayo, AP: Arroyo Paretas, R76: Ruta 76, SC: San Carlos, GA: Golpe de Agua. Sauce Grande Formation is the base of the sequence and GC locality is the top). (b) Simplified curve that shows the evolution of the deformation. SD in red: spasmodic (stronger) moments of the deformation. The arrows indicate the increase of the shortening, from the top to the base, as the deformation decrease at the top of the sequence. Comparison with conceptual models [<i>Saint-Bezar et al.</i>, 2002; <i>Parés and van der Pluijm</i>, 2003; <i>Weil and Yonkee</i>, 2009] showed in (c). There are changes in the shape of the ellipsoids, from triaxial to prolate and oblate indicating a migration from tectonic to sedimentary fabric in all the cases.
AMS data of the different localities of the Tunas Formation situated in Sierra de las Tunas, Sier... more AMS data of the different localities of the Tunas Formation situated in Sierra de las Tunas, Sierra de Pillahuincó and Claromecó Basin, from de base to the top: AMS ellipsoids with structural correction, with horizontal bedding planes, and ratio between the degree of anisotropy (P<sub>j</sub>) and the shape parameter (T), with the average values in red.
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Papers by Renata Nela Tomezzoli