DOCSLIB.ORG

Digital Processing of Satellite Images Applied to the Epithermal Ore Deposits Exploration, Santa Cruz Province, Argentina

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Digital Processing of Satellite Images Applied to the Epithermal Ore Deposits Exploration, Santa Cruz Province, Argentina Digital processing of satellite images applied to the epithermal ore deposits exploration, Santa Cruz province, Argentina. 1Gómez, J.C., 1de Barrio, R.E., 1-2Schalamuk, I. and 1-2Lopez, R. 1. Instituto de Recursos Minerales, F.C.N.yM. (UNLP). 2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). [email protected] Abstract –In the Deseado Massif, southern Argentina there are many gold and silver epithermal deposits, some of them in exploitation. These deposits area associated to basic to acid volcanic and piroclastic rocks, Jurassic in age, belonging to Bajo Pobre, Chon Aike and La Matilde Formations. Epithermal precious metal deposits correspond to low sulfidation type. Hydrothermal alteration processes (silicification, argillization and propilitization) have not generated big halos or are covered by modern sediments. For these reasons such processes can not be identified through traditional methodologies. The digital processing of Landsat 7 images was used with the objective of founding new targets. In this way several tasks were undertaken i.e. geometric correction, HIS enhancement and digital analysis. This methodology has allowed to identified areas with argillic alteration that were not observed in the satellite images without special processing latterly confirmed with field work. I. INTRODUCTION Fig. 1 Work area location In the Deseado Massif, southern Argentina there are many gold epithermal deposits, which have been Upper Jurassic, whose deposits refer to Bahía Laura partially studied and explored by costeaning and Group, which is made up of the Chon Aike and La Matilde Formations. perforations. The main ore deposit is the Cerro Vanguardia mine, in exploitation since 1998. The first Formation is mainly of acid composition. It As part of the research of those epithermal deposits, consists of lavas and ash flow tuffs. The lavic facies that are being taken for the Instituto de Recursos (Figure #3) are light colored, characterized by Minerales (Universidad Nacional de La Plata) in the subrounded outcrops which reach hundreds of Deseado Massif Geological Province, it was made meters in diameter, its scarce porphyrism and the digital processing of Landsat 7 images in the mesoscale flow banding. On the other hand, the ash northwestern region (69° 45’ to 70° 30’ W Long., flow tuffs (Figure #4) are red, brown or yellowish and 46° 30’ to 47° 30’ S. Lat., Figure 1) with the colored, forming thick broad units with variable welding degree. objective of founding new targets. In this way several tasks were undertaken i.e. geometric La Matilde Formation rocks are principally tuffs correction, HIS enhancement and ratios that permit and reworked sediments. identified hydrothermal alteration zones latterly Cretaceous sedimentary and pyroclastic rocks from confirmed with support of field work. Chubut Group and Tertiary sediments belonging to II. GEOLOGICAL SETTING the Golfo San Jorge Basin, outcrop all over the northern studied area. Usually these rocks are In the studied area, the oldest stratigraphical unit covered by tertiary basalts in outcrops affected by belongs to the volcanic rocks of the Bajo Pobre fluvial and eolic erosion. They are withish and Formation (Middle Jurassic). Such unit is composed locally well stratificated. of andesitic and basandesitic lavas and dominant Tertiary basalts begin to spread out towards the grayish, greenish, violet volcanic agglomerates with North of the studied area. Their thickness amounts to a high alteration. The following volcanic unit which a few meters only. They belong to the so-called involves the greatest area, belongs to the Middle- A B 20 Km Km Fig. 2 Digital processing of Landsat 7 images A: Geological image Fusion IHS RGB 742 + Panchromatic. B: Epithermal alteration Image, Fusion Intensity RGB 742 + 5/7 ratio. Arrows show argillic alteration zones and associated lavic lithologies (Chon Aike Formation). Basalto Cerro Sombrero and its equivalents and fall Such processes can not be identified through within the Eocen-Oligocen age. traditional methodologies. Tertiary basalts of possible Mio-Pliocen age outcrop Hydrothermal alteration mainly consists of in the southern area. Usually, they appear as silicification, argillization and in less proportion subhorizontal levels, overlying Jurassic as well as propilitization. Tertiary Formations. Their presence in the area is very scarce. IV. METODOLOGY a) GEOMETRICAL CORRECTION III.. MINERALIZATIONS Epithermal gold and silver deposits correspond to In order to carry out this work, it was necessary to take basic information spatially refferenciated. For low sulphidation type and have different emplacements such as: veins, veinlets, stockworks this reason Landsat 7 (TM +ETM) Path 229 Row 93 and 94 images were used. A field trip was made to and scarce disseminations. (Schalamuk et al., 1997, take control points, using GPS technology. 1999, 2002) The vein shaped ones can be up to a few hundreds Before this, the field work was planned taking into meters long and their maximum thickness is from 2 account many points: the particular spatial resolution of the images, the maximum permit error, possibility to 3 meters. They are essentialy made up of siliceous material (quartz, chalcedony, opal) and very scarce of access to punctual places and the spatial distribution of points (Lillesand and Kiefer, 2000, sulphurs. The ore is composed by native gold, Gao, 2001). electrum, native silver and some silver sulphosalts. Hydrotermal alteration processes, which have not Thirty GPS points were also taken using a Garmin generated big halos or which are covered by modern E’trex Submit with a planimetric error between 8 sediments, are associated with these mineralizations. and 15 mts. The points were located using natural Figure 3 Acid lava outcrops , Chon Aike Formation, southem of del Infierno Creek Figure 4 Rhyolitic ash flow tuff, Chon Aike Formation, southem of del Infierno Creek. and human features as reference, easily visible in the and Campo Inchauspe geodetic datum, with a images. planimetric error (rms) from 25 to 30 m, and an For the digital processing the software ER Mapper spatial resolution of 15 m (pixel size). To perform V. 6.2 was employed. Using different processing the geometrical correction a first order polynomial images techniques and the information taken in the was used and the resampling system was the cubic field work a geometrical correct image was convolution. generated in a map projection Gauss Krüger Band 2 b) LANDSAT 7 IMAGE ENHANCEMENT AND DIGITAL reasonable to think in a genetic linking even though ANALYSIS PROCESS it rest more research to confirm this. RGB algorithms were generated matching different - Altered lava outcrops are regionally aligned with a bands, looking for a particular enhance in order to main orientation NW-SE and subserviently WNW- discriminate the different facies of Chon Aike ESE and NE-SW. Formation. Then using HIS fusion algorithms - The above mentioned method enables to identify (Intensity, Hue, Saturation), RGB combinations argilitic alteration areas which are not visible in were jointed with the 15 m. resolution Panchromatic satellite images with normal vision. Therefore, this image, reaching to different products. method is useful for exploration purposes, since For image enhancement the following steps were these characteristics are truly related to epithermal used: Au and Ag mineralizations in other areas of the a) Directional spatial filters were carried out, using Deseado Massif. the panchromatic band to remark the linear features and then the interpretation and mapping of these VI. ACKNOWLEDGMENTS structures. Statistical treatment has allowed to Authors thank Agencia Nacional de Promoción establish three main fracturation systems: NW-SE, Científica y Tecnológica (FONCyT) and NE-SW and N-S. FOMICRUZ S.E., Research Project BID b) Anaglyphs, overlapping two neighbor images for 802/OC.AR PID 32/98, whose support this 3D interpretation. investigation. c) Digital RGB fusion, making merges between VII. REFERENCES regular and panchromatic bands. J. Gao, 2001. Non-Differential GPS as an alternative source of DIGITAL ANALYSIS planimetric control for rectifying satellite imagery. Photogrammetric engineering & Remote sensing (PE In a second stage, algorithms with bands ratio & RS), 67: 49-56. Maryland. (Ratios algorithms) were made, i.e. RGB 7,4,2 + 5/7 S. Lillesand and R. Kiefer, 2000. Remote sensing and image interpretation. 4th edition. John Wiley & Sons Inc. 724 (Sabine, 1999) with the intention of discriminate the pgs. pattern of known mineralized areas in lavic facies of Ch.Sabine, 1999. Remote sensing strategies for mineral the ignimbritic – lavic Jurassic complex and related exploration. En A. Rencz (editor): Remote sensing for argillic hydrotermally altered zones in other areas. the Earth sciences, pg.: Cap. 8: 375-428. John Wiley & Sons, Inc. New York. In the next step the work was pointed out in I.B. Schalamuk; M.A. Zubia, A. Genini, R.R. Fernández, 1997. extrapolations the small lithological differences Jurassic epithermal Au-Ag deposits of Patagonia, Argentina. Ore Geology Rewiew. (ed. Elsevier) Vol 12, watched to the whole area of study, getting 20 new Nro. 3: 173-186. areas subsequently researched at the field work, I.B. Schalamuk, R. E. de Barrio, M.A. Zubia, A.Genini and H. where the observations allow to confirm that the Echeveste, 1999. Provincia auroargentífera del pointed areas were lavic lithologies with argillic Deseado, Santa Cruz. En Recursos minerales de la República
Load more

Recommended publications
  • Tetrapod Track Assemblages from Lower Cretaceous Desert Facies In
    Palaeogeography, Palaeoclimatology, Palaeoecology 507 (2018) 1–14 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Tetrapod track assemblages from Lower Cretaceous desert facies in the Ordos Basin, Shaanxi Province, China, and their implications for Mesozoic T paleoecology ⁎ Lida Xinga,b,c, Martin G. Lockleyd, , Yongzhong Tange, Anthony Romiliof, Tao Xue, Xingwen Lie, Yu Tange, Yizhao Lie a State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China b School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China c State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China d Dinosaur Trackers Research Group, CB 172, University of Colorado at Denver, PO Box 173364, Denver, CO 80217-3364, USA e Shaanxi Geological Survey, Xi'an 710054, Shaanxi, China f School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia ARTICLE INFO ABSTRACT Keywords: Tetrapod ichnofaunas are reported from desert, playa lake facies in the Lower Cretaceous Luohe Formation at Ichnofacies Baodaoshili, Shaanxi Province, China, which represent the first Asian example of an ichnnofauna typical of the Brasilichnium Chelichnus Ichnofacies (Brasilichnium sub-ichnofacies) characteristic of desert habitats. The mammaliomorph Sarmientichnus tracks, assigned to Brasilichnium,
    [Show full text]
  • Geologica Acta, Vol.4, N°4, 2006, 409-438 |415| Ce
    'geológica FOmS^Y ACTA GEOLÓGICA HISPAfilCA Geológica acta: an international earth science journal Universidad de Barcelona [email protected] ISSN (Versión impresa): 1695-6133 ESPAÑA 2006 C.C. Labandeira THE FOUR PHASES OF PLANT-ARTHROPOD ASSOCIATIONS IN DEEP TIME Geológica acta: an international earth science journal, december, año/vol. 4, número 004 Universidad de Barcelona Barcelona, España pp. 409-438 Red de Revistas Científicas de América Latina y el Caribe, España y Portugal ®re¿!alyc^ Universidad Autónoma del Estado de México http://redalyc.uaemex.mx Geológica Acta, Vol.4, N° 4, 2006, 409-438 Appendix l-IX geología acta Available online at www.geologica-acta.com The Four Phases of Plant-Arthropod Associations in Deep Time C.C. LABANDEIRA |1||2| 111 Smithsonian Institution, National Museum of Natural History P.O. Box 37012, MRC-121 Department of Paleobiology, Washington, D.C., USA 200137012. E-mail: [email protected] 121 University of Maryland, Department of Entomology College Park, Maryland, USA 20742 1 ABSTRACT I Vascular-plant hosts, their arthropod herbivores, and associated functional feeding groups are distributed spa- tiotemporally into four major herbivore expansions during the past 420 m.y. They are: (1) a Late Silurian to Late Devonian (60 m.y.) phase of myriapod and apterygote, hexapod (perhaps pterygote) herbivores on several clades of primitive vascular-plant hosts and a prototaxalean fungus; (2) a Late Mississippian to end-Permian (85 m.y.) phase of mites and apterygote and basal pterygote herbivores on pteridophyte and basal gymnospermous plant hosts; (3) a Middle Triassic to Recent (245 m.y.) phase of mites, orthopteroids (in the broadest sense) and hemipteroid and basal holometabolan herbivores on pteridophyte and gymnospermous plant hosts; and (4) a mid Early Cretaceous to Recent (115 m.y.) phase of modern-aspect orthopteroids and derived hemipteroid and holometabolous herbivores on angiospermous plant hosts.
    [Show full text]
  • Occurrence of Sauropod Dinosaur Tracks in the Upper Jurassic of Chile (Redescription of Iguanodonichnus Frenki)
    Journal of South American Earth Sciences 20 (2005) 253–257 www.elsevier.com/locate/jsames Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription of Iguanodonichnus frenki) Karen Moreno *, Michael J. Benton Earth Sciences Department, University of Bristol, Bristol BS8 1RJ, UK Received 7 July 2003; accepted 20 May 2005 Abstract New observations from the only studied Upper Jurassic dinosaur unit in South America, the Ban˜os del Flaco Formation, Chile, are presented herein. The original description of the ichnospecies Iguanodonichnus frenki contains several mistakes and information that needs updating. Therefore, we provide a redescription, including new data collected in the field, that supports I. frenki as a sauropod in origin on the basis of the following features: step angles average less than 1108; pes prints intersect the trackway midline; pes prints are longer than wide, with the long axis rotated outward; the claw impression of digit I is prominent and directed forward; and claws on digits II, III, and IV are strongly reduced. These morphological characteristics might give clues about the pes morphology of the South American Jurassic sauropods, whose foot bone remains are scarce. The presence of this sauropod ichnospecies in the Late Jurassic agrees with Early–Middle Jurassic faunal associations in South America. q 2005 Elsevier Ltd. All rights reserved. Keywords: Chile; Dinosaur footprints; Parabrontopodus; Sauropod; Upper Jurassic Resu´men En el presente trabajo se realizan nuevas observaciones acerca de las huellas de dinosaurios de la Formacio´n Ban˜os del Flaco, las cuales representan el u´nico registro conocido para Jura´sico Superior en Ame´rica del Sur.
    [Show full text]
  • Die Fossilen Araucaria-Zapfen Der La Matilde Formation Im Versteinerten Wald Von Cerro Cuadrado in Patagonien (Süd-Argentinien) Veit Martin Dörken & Hilke Steinecke
    Die fossilen Araucaria-Zapfen der La Matilde Formation im versteinerten Wald von Cerro Cuadrado in Patagonien (Süd-Argentinien) Veit Martin Dörken & Hilke Steinecke Abstract Due to a volcanic eruption, the Araucaria dominated Jurassic forest of Cerro Cuadrado (Patagonia) got very well preserved. Particularly the seed cones of Araucaria mirabilis (Araucariaceae) belong to the most spectacular fossils of this formation. Their morphology is outlined. Zusammenfassung Durch einen Vulkanausbruch vor rund 160 Mio. Jahren wurde die damalige jurassische, von Araukarien dominierte Waldforma- tion von Cerro Cuadrado (Patagonien) in einer einzigartigen Qualität konserviert. Zu den spektakulärsten Fossilien zählen hier zweifelsohne die Samenzapfen von Araucaria mirabilis (Araucariaceae), die nachfolgend vorgestellt werden. 1. Einleitung Die Familie hatte früher ein wesentlich weiteres Die Araukariengewächse (Araucariaceae) wie auch Verbreitungsareal, als das heutige Artenspektrum die Gattung Araucaria selbst, sind eine erdge- dies noch vermuten lässt. So waren die Araucaria- schichtlich sehr alte Gruppe von Gymnospermen ceae im Erdmittelalter (Mesozoikum, vor rund 250 (= Nacktsamern). Ihr Ursprung liegt wahrschein- bis 100 Mio. Jahren) auch auf der Nordhemisphä- lich im Trias-Zeitalter (vor rund 250–200 Mio. re verbreitet, während sich die heutige Verbreitung Jahren, Kunzmann 2007; Zonneveld 2012). ausschließlich auf die Südhemisphäre beschränkt Abb. 1: Einst als kleines, langsam wachsendes Bäumchen in einem Vorgarten in Dortmund-Wambel gepflanzt und mittlerweile haushoch: Männliches Exemplar von Araucaria Abb. 2: Zweig von Araucaria araucana mit Pollenzapfen. araucana. (Foto: G. Steinecke) (Foto: G. Steinecke) 18 Der Palmengarten 84/1 die Gewebestrukturen im Detail studiert werden. Durch die Bedeckung mit Vulkanasche kam es zur Verkieselung der Pflanzenteile (Taylor et al. 2009). Männliche Pollenzapfen wurden im ver- steinerten Wald von Cerro Cuadrado so gut wie nicht nachgewiesen (Dernbach 1992, Taylor et al.
    [Show full text]
  • Dinosaurs (Reptilia, Archosauria) at Museo De La Plata, Argentina: Annotated Catalogue of the Type Material and Antarctic Specimens
    Palaeontologia Electronica palaeo-electronica.org Dinosaurs (Reptilia, Archosauria) at Museo de La Plata, Argentina: annotated catalogue of the type material and Antarctic specimens Alejandro Otero and Marcelo Reguero ABSTRACT A commented-illustrated catalogue of non-avian dinosaurs housed at Museo de La Plata, Argentina is presented. This represents the first commented catalogue of the La Plata Museum dinosaurs to be published. This includes the type material as well as Antarctic specimens. The arrangement of the material was made in a phylogenetic fashion, including systematic rank, type material, referred specimens, geographic and stratigraphic location, and comments/remarks, when necessary. A total of 13 type specimens of non-avian dinosaurs are housed at the collection of Museo de La Plata, including eight sauropods, one theropod, one ornithischian, and three ichnotaxa. There are four Antarctic specimens, one of which is a holotype, whereas other corresponds to the first sauropod dinosaur registered for that continent. Alejandro Otero. División Paleontología de Vertebrados, Museo de La Plata. Paseo del Bosque s/n (1900), La Plata, Argentina. [email protected] Marcelo Reguero. División Paleontología de Vertebrados, Museo de La Plata. Paseo del Bosque s/n (1900), La Plata, Argentina. [email protected] Keywords: Saurischia; Ornithischia; Holotype; Lectotype; Patagonia; Antarctica INTRODUCTION housed at the DPV collection, reaching more than 600 individual bones. These include 13 type mate- The Museo de La Plata (MLP), constructed in rial and otherwise important dinosaur specimens, 1884, is one of the oldest museums of natural his- which include ornithischians (e.g., ornithopods, tory of South America. The collection of the ankylosaurs), saurischians (e.g., theropods, sau- División Paleontología de Vertebrados (DPV) was ropodomorphs), as well as three ichnospecies created in 1877 when the museum’s future Direc- included (see Table 1 for a summary of the taxa tor, Dr.
    [Show full text]
  • X Congreso Argentino De Paleontología Y Bioestratigrafía VII Congreso Latinoamericano De Paleontología La Plata, Argentina - Septiembre De 2010
    X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 Financian Auspician 1 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 2 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 3 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 X Congreso Argentino de Paleontología y Bioestratigrafía y VII Congreso Latinoamericano de Paleontología Resúmenes/coordinado por Sara Ballent ; Analia Artabe ; Franco Tortello. 1a ed. - La Plata: Museo de la Plata; Museo de la Plata, 2010. 238 p. + CD-ROM; 28x20 cm. ISBN 978-987-95849-7-2 1. Paleontología. 2. Bioestratigrafía. I. Ballent, Sara , coord. II. Artabe, Analia, coord. III. Tortello, Franco, coord. CDD 560 Fecha de catalogación: 27/08/2010 4 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología Declarado de Interés Municipal, La Plata (Decreto N° 1158) 5 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 6 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología La Plata, Argentina - Septiembre de 2010 X Congreso Argentino de Paleontología y Bioestratigrafía VII Congreso Latinoamericano de Paleontología Prólogo Una vez más el Congreso Argentino de Paleontología y Bioestratigrafía y el Congreso Latino- americano de Paleontología se realizan de manera conjunta.
    [Show full text]
  • Theropod Dinosaurs from Argentina
    139 Theropod dinosaurs from Argentina Martín D. EZCURRA1 & Fernando E. NOVAS2 1CONICET, Sección Paleontología Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Angel Gallardo 470, Buenos Aires, C1405DJR, Argentina. [email protected], Laboratorio de Anatomía Comparada y Evolución de los Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Ángel Gallardo 470, Buenos Aires, C1405DJR, Argentina. [email protected] Abstract. Theropoda includes all the dinosaurs more closely related to birds than to sauropodomorphs (long-necked dinosaurs) and ornithischians (bird-hipped dinosaurs). The oldest members of the group are early Late Triassic in age, and non-avian theropods flourished during the rest of the Mesozoic until they vanished in the Cretaceous-Palaeogene mass extinction. Theropods radiated into two main lineages, Ceratosauria and Tetanurae, which are well represented in Cretaceous rocks from Argentina. Ceratosaurians are the most taxonomically diverse South American non-avian theropods, including small to large-sized species, such as the iconic horned dinosaur Carnotaurus. Argentinean tetanurans are represented by multiple lineages that include some of the largest carnivorous dinosaurs known worldwide (carcharodontosaurids), the enigmatic large-clawed megaraptorans, and small to medium-sized species very closely related to avialans (e.g. unenlagiids). The Argentinean non-avian theropod record has been and is crucial to understand the evolutionary and palaeobiogeographical
    [Show full text]
  • Coniferous Wood of Agathoxylon from the La Matilde Formation, (Middle Jurassic), Santa Cruz, Argentina
    Journal of Paleontology, page 1 of 22 Copyright © 2018, The Paleontological Society 0022-3360/15/0088-0906 doi: 10.1017/jpa.2017.145 Coniferous wood of Agathoxylon from the La Matilde Formation, (Middle Jurassic), Santa Cruz, Argentina Adriana C. Kloster,1 and Silvia C. Gnaedinger2 1Área de Paleontología, Centro de Ecología Aplicada del Litoral, Consejo Nacional de Investigaciones Científicas y Técnicas (CECOAL-CCT CONICET Nordeste-UNNE). 〈[email protected]〉 2Área de Paleontología, Centro de Ecología Aplicada del Litoral, Consejo Nacional de Investigaciones Científicas y Técnicas (CECOAL-CCT CONICET Nordeste-UNNE), Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste (FaCENA-UNNE). Casilla de Correo 291, 3400 Corrientes, Argentina, 〈[email protected]〉 Abstract.—In this contribution, four species of Agathoxylon are described from the La Matilde Formation, Gran Bajo de San Julián and central and south-western sectors of Santa Cruz Province, Argentina. Agathoxylon agathioides (Kräusel and Jain) n. comb., Agathoxylon santalense (Sah and Jain) n. comb., Agathoxylon termieri (Attims) Gnaedinger and Herbst, and the new species Agathoxylon santacruzense n. sp. are described based on a detailed description of the secondary xylem. In this work, it was possible to construct scatter plots to elucidate the anatomical differences between the fossil species described on quantitative anatomical data. Comparisons are made with other Agathoxylon species from Gondwana. These parameters can be used to discriminate genera and species of wood found in the same formation, as well as to establish differences/similarities between other taxa described in other formations. Some localities contain innumerable “in situ” petrified trees, which allowed us to infer that these taxa formed small forests, or local forests, or small forests within a dense forest, which is a habitat coincident with the extant Araucariaceae.
    [Show full text]
  • Efficient Chrono-Stratigraphic Database Structure in GIS Carlos Gabriel Asato, Servicio Geológico Minero Argentino Buenos Aires, Argentina
    Efficient Chrono-Stratigraphic Database Structure in GIS Carlos Gabriel Asato, Servicio Geológico Minero Argentino Buenos Aires, Argentina. E-mail [email protected] Abstract In recent years the Instituto de Geología Regional y Recursos Minerales, has been developing the Regional Geology GIS Data Standards. One of the most important tasks was the development of the chrono-stratigraphic database definition and design. In order to allow the use and exploitation of digital geological maps, a simple database structure had been made. This case differs from traditional chrono- stratigraphic database designs where there are only direct relationships between geological units and their chrono-stratigraphic definition. The design concept involves a hierarchical data organization taken from the chrono-stratigraphic column where the relationships between classes and sub- classes were preserved. In more detail it is used a special code definition that was designed in order to have a direct correspondence with a specific chrono-stratigraphic division, and indirect relation to their own hierarchical position. There is also a complete chrono-stratigraphic definition, ordered in separate fields, and organized by chrono-stratigraphic level. The data structure formed by geological layer, table relationships, chrono-stratigraphic code and chrono- stratigraphic table design allow to the users indexing, classification, and direct searching and scalable design. Introducction GIS design involves a lot of different analysis techniques based in the analysis of data spatial structures, attribute tables and related database. Analysis could be made using GIS tools, only if data structures have an appropriate design. Database design could be understood as important GIS part when querying analysis will be performed.
    [Show full text]
  • A New Middle–Late Jurassic Flora and Hot Spring Chert Deposit from The
    Geol. Mag. 144 (2), 2007, pp. 401–411. c 2007 Cambridge University Press 401 doi:10.1017/S0016756807003263 Printed in the United Kingdom A new Middle–Late Jurassic flora and hot spring chert deposit from the Deseado Massif, Santa Cruz province, Argentina ALAN CHANNING∗, ALBA B. ZAMUNER† & ADOLFO ZU´ NIGA˜ † ∗School of Earth, Ocean & Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE, UK †Departamento de Paleobotanica,´ Facultad de Ciencias Naturales y Museo, UNLP, Paseo del Bosque s/n◦, 1900 La Plata, Argentina (Received 14 March 2006; accepted 1 August 2006) Abstract – We present an initial report of a well-preserved and relatively diverse Gondwanan plant assemblage from Bah´ıa Laura Group, Chon Aike Formation strata of the Estancia Flecha Negra area, central-western region of the Deseado Massif, Santa Cruz province, Patagonia, Argentina. The locality contains the first richly fossiliferous chert with a diverse and well-preserved plant assemblage reported from the Mesozoic which is demonstrably associated with hot spring activity. A compression flora and petrified forest contained in associated clastic and volcaniclastic environments provide an indication of regional plant diversity during this as yet poorly represented stratigraphic interval. Keywords: silicification, sinter, epithermal, permineralized, permineralised, petrified. 1. Introduction 2. Regional geological setting The volcanic and volcaniclastic Bah´ıa Laura Group of The Deseado Massif, Santa Cruz province, Argentina, Santa Cruz province, Patagonia, Argentina, contains is part of a major Jurassic bimodal volcanic province, a diverse, often well-preserved and important Middle related to widespread extensional tectonism, which to Late Jurassic, Gondwanan flora (Table 1). To date, extends across Patagonia and Antarctica (Pankhurst floras have been recorded from the tuff-dominated La et al.
    [Show full text]
  • A Diverse Mammal-Dominated, Footprint Assemblage from Wetland
    www.nature.com/scientificreports OPEN A diverse mammal-dominated, footprint assemblage from wetland deposits in the Lower Cretaceous of Received: 6 September 2017 Accepted: 12 December 2017 Maryland Published: xx xx xxxx Ray Stanford1, Martin G. Lockley2, Compton Tucker3, Stephen Godfrey4 & Sheila M. Stanford1 A newly discovered assemblage of predominantly small tracks from the Cretaceous Patuxent Formation at NASA’s Goddard Space Flight Center, Maryland, reveals one of the highest track densities and diversities ever reported (~70 tracks, representing at least eight morphotypes from an area of only ~2 m2). The assemblage is dominated by small mammal tracks including the new ichnotxon Sederipes goddardensis, indicating sitting postures. Small crow-sized theropod trackways, the frst from this unit, indicate social trackmakers and suggest slow-paced foraging behavior. Tracks of pterosaurs, and other small vertebrates suggest activity on an organic-rich substrate. Large well-preserved sauropod and nodosaurs tracks indicate the presence of large dinosaurs. The Patuxent Formation together with the recently reported Angolan assemblage comprise the world’s two largest Mesozoic mammal footprint assemblages. The high density of footprint registration at the NASA site indicates special preservational and taphonomic conditions. These include early, penecontemporaneous deposition of siderite in organic rich, reducing wetland settings where even the fesh of body fossils can be mummifed. Thus, the track-rich ironstone substrates of the Patuxent Formation, appear to preserve a unique vertebrate ichnofacies, with associated, exceptionally-preserved body fossil remains for which there are currently no other similar examples preserved in the fossil record. Reports of true Mammalia tracks, from the Mesozoic, as distinct from tracks of presumed synapsids (therap- sids) from early Mesozoic (mostly Triassic and Jurassic) dune facies, are rare, and mostly involve very small samples of isolated tracks.
    [Show full text]
  • Dinosaurs (Reptilia, Archosauria) at Museo De La Plata, Argentina: Annotated Catalogue of the Type Material and Antarctic Specimens
    Palaeontologia Electronica palaeo-electronica.org Dinosaurs (Reptilia, Archosauria) at Museo de La Plata, Argentina: annotated catalogue of the type material and Antarctic specimens Alejandro Otero and Marcelo Reguero ABSTRACT A commented-illustrated catalogue of non-avian dinosaurs housed at Museo de La Plata, Argentina is presented. This represents the first commented catalogue of the La Plata Museum dinosaurs to be published. This includes the type material as well as Antarctic specimens. The arrangement of the material was made in a phylogenetic fashion, including systematic rank, type material, referred specimens, geographic and stratigraphic location, and comments/remarks, when necessary. A total of 13 type specimens of non-avian dinosaurs are housed at the collection of Museo de La Plata, including eight sauropods, one theropod, one ornithischian, and three ichnotaxa. There are four Antarctic specimens, one of which is a holotype, whereas other corresponds to the first sauropod dinosaur registered for that continent. Alejandro Otero. División Paleontología de Vertebrados, Museo de La Plata. Paseo del Bosque s/n (1900), La Plata, Argentina. [email protected] Marcelo Reguero. División Paleontología de Vertebrados, Museo de La Plata. Paseo del Bosque s/n (1900), La Plata, Argentina. [email protected] Keywords: Saurischia; Ornithischia; Holotype; Lectotype; Patagonia; Antarctica INTRODUCTION housed at the DPV collection, reaching more than 600 individual bones. These include 13 type mate- The Museo de La Plata (MLP), constructed in rial and otherwise important dinosaur specimens, 1884, is one of the oldest museums of natural his- which include ornithischians (e.g., ornithopods, tory of South America. The collection of the ankylosaurs), saurischians (e.g., theropods, sau- División Paleontología de Vertebrados (DPV) was ropodomorphs), as well as three ichnospecies created in 1877 when the museum’s future Direc- included (see Table 1 for a summary of the taxa tor, Dr.
    [Show full text]