Pardo-Iguzquiza E.,Instituto Geologico |
Duran J.J.,Instituto Geologico |
Dowd P.A.,University of Adelaide
Acta Carsologica | Year: 2013
Digital elevation models (DEM) are digital representations of topography that are especially suitable for numerical terrain analysis in earth sciences and engineering. One of the main quantitative uses of DEM is the automatic delineation of flow networks and watersheds in hydrology and geomorphology. In these applications (using both low-resolution and precision DEM) depressions hinder the inference of pathways and a lot of work has been done in designing algorithms that remove them so as to generate depression-free digital elevation models with no interruptions to flow. There are, however, geomorphological environments, such as karst terrains, in which depressions are singular elements, on scales ranging from centimetres to kilometres, which are of intrinsic interest. Te detection of these depressions is of significant interest in geomorphologic mapping because the development of large depressions is normal in karst terrains: potholes, blind valleys, dolines, uvalas and poljes. Te smallest depressions that can be detected depend on the spatial resolution (pixel size) of the DEM. For example, depressions from centimetres to a few metres, such as some types of karren, cannot be detected if the raster digital elevation model has a spatial resolution greater than, say, 5 m (i.e., square 5m pixel). In this work we describe a method for the automatic detection and delineation of terrain depressions. First, we apply a very efficient algorithm to remove pits from the DEM. Te terrain depressions are then obtained by subtracting the depression-free DEM from the original DEM. Te fnal product is a digital map of depressions that facilitates the cal-culation of morphometric features such as the geometry of the depressions, the mean depth of the depressions, the density of depressions across the study area and the relationship between depressions and other variables such as altitude. Te method is illustrated by applying it to data from the Sierra de las Nieves karst massif in the province of Málaga in Southern Spain. This is a carbonate aquifer that is drained by three main springs and in which the depressions play an important role in the recharge of the aquifer. A doline density map, produced from a map of 324 detected dolines/uvalas, identifes three main recharge areas of the three springs. Other morphometric results related to the size and direction of the dolines are also presented. Finally the dolines can be incorporated into a geomorphology map.
Campbell K.E.,Vertebrate Zoology |
Prothero D.R.,Occidental College |
Romero-Pittman L.,Instituto Geologico |
Hertel F.,Northridge |
Rivera N.,Occidental College
Journal of South American Earth Sciences | Year: 2010
The chronostratigraphy of the youngest Neogene deposits of the Amazon Basin, which comprise the Madre de Dios Formation in eastern Peru, remains unresolved. Although 40Ar/39Ar dates on two volcanic ashes from this formation in Peru provide critical baseline data points, stratigraphic correlations among scattered riverine outcrops in adjacent drainage basins remain problematic. To refine the chronostratigraphy of the Madre de Dios Formation, we report here the magnetostratigraphy of an outcrop on the Madre de Dios River in southeastern Peru. A total of 18 polarity zones was obtained in the ∼65-m-thick Cerro Colorado section, which we correlate to magnetozones Chrons C4Ar to C2An (9.5-3.0Ma) based on the prior 40Ar/39Ar dates. These results confirm the late Miocene age of a gomphothere recovered from the Ipururo Formation, which underlies the late Miocene Ucayali Unconformity at the base of the Cerro Colorado outcrop. The results also support earlier interpretations of a late Miocene age for other fossils of North American mammals recovered from basal conglomeratic deposits of the Madre de Dios Formation immediately above the Ucayali Unconformity. These mammals include other gomphotheres, peccaries, and tapirs, and their presence in South America in the late Miocene is recognized as part of the first pulse of the Great American Faunal Interchange. © 2009 Elsevier Ltd.
Modenesi-Gauttieri M.C.,Instituto Geologico |
de Toledo M.C.M.,University of Sao Paulo |
Hiruma S.T.,Instituto Geologico |
Taioli F.,University of Sao Paulo |
Shimada H.,Instituto Geologico
Catena | Year: 2011
The thick weathering profiles of humid tropical areas are an important, yet generally neglected, source of information on landscape evolution. Six complete profiles of the weathering mantle were sampled by drilling on the three stepped levels of the Campos do Jordão Plateau, on the NW flank of the Continental Rift of Southeastern Brazil. Mineralogical and micromorphological analyses of drill core samples, complemented by geochemical interpretations and by previous data on the upper saprolite, indicate continuity of a general lateritic trend during the entire process of mantle formation. Lateritization phases of different intensity were defined and considered to reflect adjustment to changes in environmental conditions created by the gradual uplift of the plateau to its present position. Older and more superficial materials related to intense lateritic weathering are characterized by allitization with direct formation of gibbsite from silicates, probably related to tropical climates existing immediately before the formation of the continental rift, during the Paleogene, and also before any significant increase in altitude. Monosialitization phase with general kaolinitization and restricted indirect formation of gibbsite from silicates could be associated to less aggressive climates that followed the Neogene (Miocene?) accentuation of uplift rates along the continental rift. The changes produced by uplift in the tropical climate eventually favored the development of a podzolization trend in soils above 1800. m. © 2011 Elsevier B.V.
Hiruma S.T.,Instituto Geologico |
Modenesi-Gauttieri M.C.,Instituto Geologico |
Riccomini C.,University of Sao Paulo
Boreas | Year: 2013
Despite the generalized occurrence of colluvial deposits in the humid tropical areas of southeastern Brazil, regional correlation is difficult because the deposits are discontinuous, and chronological data are very scarce and scattered. For the first time, colluvial deposits in the Bocaina Plateau are described, including 18 radiocarbon ages from 12 profiles. The plateau is located on the eastern flank of the Continental Rift of Southeastern Brazil and is the highest part of the Serra do Mar, with elevations up to 2000m above sea level. Because the Bocaina Plateau is part of the summit surfaces of southeastern Brazil, it was subjected to specific climatic conditions during the Quaternary. Colluvial deposits on the lower hillslopes and edges of amphitheatres can show complex sequences with up to three intercalated dark humic horizons, corresponding to Late Pleistocene and Holocene phases of morphodynamic activity and pedogenesis. Ages of palaeosols vary from 650±50 a BP to 36880±980 a BP. Landforms and colluvia on the Bocaina Plateau are very similar to those found on the opposite flank of the continental rift, on the Campos do Jordão Plateau. Ages of buried soils point to similar soil formation and colluviation episodes in the two plateaus. As in Campos do Jordão, the succession of erosive, depositional and pedogenetic processes on the altos campos hillslopes is probably related to late Quaternary climate changes. © 2012 The Authors. Boreas © 2012 The Boreas Collegium.
Hiruma S.T.,Instituto Geologico |
Hiruma S.T.,University of Sao Paulo |
Riccomini C.,University of Sao Paulo |
Modenesi-Gauttieri M.C.,Instituto Geologico |
And 3 more authors.
Gondwana Research | Year: 2010
The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5. Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200. Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins. © 2010 International Association for Gondwana Research.
Souza P.A.,Federal University of Rio Grande do Sul |
Felix C.M.,Federal University of Rio Grande do Sul |
Perez-Aguilar A.,Instituto Geologico |
Petri S.,University of Sao Paulo
Revue de Micropaleontologie | Year: 2010
The rhythmites of Itu present the best exposures of glacial varvites known in the Paraná Basin, and constitute a classic geological monument related to the Late Palaeozoic Gondwanan glaciation. Palynological results in this paper are based on rhythmites from two quarries in Itu area, central-eastern State of São Paulo, Brazil, including correlate levels of the " Itu Varvite Park" , as well as based on samples from the borehole IT-IG-85 (at 171 and 228. m) drilled also in the Itu City. Well-preserved indigenous miospores and microphytoplankton elements have been recorded. The former comprise 15 spore species and 19 pollen species, of which three are recorded for the first time in the Brazilian part of the Paraná Basin (Verrucosisporites cf. V. andersonii, Convolutispora archangelskyi and Caheniasaccites verrucosus). Microalgae include prasinophyceans (Leiosphaeridia sp., Tasmanites sp., Deusilites tenuistriatus), chlorophyceans (Botryococcus braunii) and zignemataceans (Tetraporina). The palynological content confirms a late Pennsylvanian (Kasimovian/Gzhelian) age for these rhythmites, which are assigned to the Crucisaccites monoletus interval Zone, based on the record of the eponymous pollen species and Scheuringipollenites maximus. Although very scarce, prasinophycean algae suggest low salinity marine conditions. © 2009 Elsevier Masson SAS.
Spiske M.,University of Munster |
Piepenbreier J.,University of Munster |
Benavente C.,Instituto Geologico |
Bahlburg H.,University of Munster
Earth-Science Reviews | Year: 2013
Numerous post-tsunami surveys have been conducted in the last two decades, especially since the 2004 Indian Ocean tsunami. These studies have documented a variety of characteristic sedimentary and erosional features that can be ascribed to known events. Nevertheless, the question arises whether these structures are just ephemeral or have a potential to be preserved in the geological record. This review describes the changes that have affected muddy to sandy siliciclastic tsunami deposits in Peru. Each of these was surveyed in the first months after the tsunami: Chimbote (1996), Camaná (2001) and Pisco-Paracas (2007). Here, we describe the changes we observed during re-surveys in 2007 and 2008.It has long been recognized that onshore tsunami deposits may suffer from surficial processes, tectonic movements and anthropogenic alteration. Earthquake-induced uplift or subsidence may subject a tsunami deposit to erosion or burial, respectively. Quick burial in rapidly subsiding coastal areas may enhance preservation. Deposits of the last or most landward-reaching wave may be preferentially preserved if they escape erosion by subsequent tsunami waves; however, inland areas are also vulnerable to subaerial reworking, including by wind and by humans.The Peruvian examples reviewed here show that the preservation of arid-coast tsunami deposits depends on interactions that are more complex that hitherto perceived. These involve sediment type, grain size, depositional setting, co-seismic movement, bioturbation, winds, and anthropogenic modification. In one example, all traces of the tsunami have been removed or reworked by flash floods and ocean waves. In another example, clasts on a coastal plain from tsunami-backwash began to be rounded and abraded by eolian sands immediately after the event. Eolian processes also smoothed and filled tsunami scours. By contrast, muddy tsunami deposits in certain areas escaped erosion by wind, probably because of their greater cohesion. In still another example, 0.5. m of co-seismic uplift was not enough to prevent ocean waves from removing a tsunami sand sheet that had mantled a coastal marsh. The buried record of tsunami deposits on modern coasts may therefore not fully represent the vulnerability of these regions to tsunamigenic hazards. © 2013 Elsevier B.V.
Shimada H.,Instituto Geologico
Boletim Paranaense de Geosciencias | Year: 2013
The exploitation of gold in secondary deposits started in Apiaí in the second half of the 17th century, andwas discontinuously performed until the end of the 19th century. The underground mining was initiated in 1889 in the Morro do Ouro mine and operated intermittently until 1942, when it was compulsorily closed, not operating since them. In 1998, after being abandoned for a long time, it turned into an area of public interest by a municipal law. In 2002, a proposal to turn the former mine into a geotouristic attraction was accepted by the municipality wich started the effective set up of the park in 2003. In 2004, the Parque Natural Municipal do Morro do Ouro was officially created, characterizing the conversion of an environmental liability into a geotouristic site.
Plata J.L.,Instituto Geologico |
Rubio F.M.,Instituto Geologico
Near Surface Geophysics | Year: 2011
The Lagoons of Estaña, at the Spanish pre-Pyrenees, constitute a set of natural water ponds the origin of which is not well-known, though a karstic formation is one of the hypotheses. A project is being developed with the objective of understanding the hydrological functioning of the lagoons related to underground waters. The lagoons are in Keuper and Muschelkalk rocks in contact with the main water-bearing structure of the zone, formed by a syncline of Cretaceous limestone. All the area is affected by a strong tectonics. In order to know the hydrogeological limits of this contact and to map the subsurface Triassic structures several resistivity profiles and eighteen magnetic resonance soundings (MRS) are made connecting the syncline with the lagoons and around them. Because of space limitations in the field the geographical distribution of the measurements is not the most appropriate one to detect possible karstic structures. A special strategy for the interpretation, mainly qualitative, is designed based on the pattern of the e(t) and E 0(q) curves, including a detailed verification of the geological situation of the MRS measurements to prevent errors that could occur in case of ID modelling is not appropriate. Part of the area is influenced by a high geomagnetic gradient due to the presence of basic rocks but good MRS measurements are obtained and it is demonstrated that this magnetic anomaly does not affect the lagoon area. The joint use of MRS and resistivity sections allows a correct interpretation and to establish the geometry of a hydrogeological model. © 2011 European Association of Geoscientists & Engineers.
News Article | February 23, 2017
VANCOUVER, BRITISH COLUMBIA--(Marketwired - Feb. 23, 2017) - Alianza Minerals Ltd. (TSX VENTURE:ANZ) ("Alianza" or the "Company") announces that an application has been made with the Peruvian authorities (INGEMMET - Instituto Geologico Minero y Metalúrgico) for nine concessions comprising six properties in central Peru. These new properties target base metals mineralization in the Peruvian Polymetallic Belt, a prolific region host to deposits such as the Cerro de Pasco Mine, where zinc, lead and copper ore has been mined for over 100 years. Alianza's target properties were internally generated from a study that examined a range of criteria including metallogeny, regional geology, regional structure, private and public geochemical databases, favourable CSR conditions and local knowledge. Management is planning reconnaissance exploration programs for all six of these properties once the concession grants are completed. It is anticipated that this process will be completed in Q2 2017 and reconnaissance work will commence shortly thereafter. "Alianza is acquiring these new concessions as a result of in-house generative work that identified 30 grassroots targets," stated Jason Weber, P.Geo., President and CEO of Alianza. "We are targeting large base metal deposits and this region of Peru is known for its lead and zinc production, with mines that were first developed over one hundred years ago. We are eager to visit these targets and ground-truth our ideas." Alianza's financing announced on February 15, 2017 has been increased to $625,000 for a total of 5,000,000 units. The units have also been amended to include one common share and one half common share purchase warrant valid for a three year period and now exercisable at $0.20 per share. The financing is fully subscribed and will close within 10 days. Alianza increases the chances of success in mineral exploration by using the "Prospect Generator" business model, focussing on gold and copper exploration in Latin America and Nevada. The Company has 28.3 million shares issued and outstanding, and is listed on the TSX Venture Exchange (TSX VENTURE:ANZ). Mr. Jason Weber, BSc, P.Geo., Alianza's President and CEO is a Qualified Person as defined by National Instrument 43-101. Mr. Weber supervised the preparation of the technical information contained in this release. NEITHER THE TSX VENTURE EXCHANGE NOR ITS REGULATION SERVICES PROVIDER (AS THAT TERM IS DEFINED IN THE POLICIES OF THE TSX VENTURE EXCHANGE) ACCEPTS RESPONSIBILITY FOR THE ADEQUACY OR ACCURACY OF THIS RELEASE. STATEMENTS IN THIS NEWS RELEASE, OTHER THAN PURELY HISTORICAL INFORMATION, INCLUDING STATEMENTS RELATING TO THE COMPANY'S FUTURE PLANS AND OBJECTIVES OR EXPECTED RESULTS, MAY INCLUDE FORWARD-LOOKING STATEMENTS. FORWARD-LOOKING STATEMENTS ARE BASED ON NUMEROUS ASSUMPTIONS AND ARE SUBJECT TO ALL OF THE RISKS AND UNCERTAINTIES INHERENT IN RESOURCE EXPLORATION AND DEVELOPMENT. AS A RESULT, ACTUAL RESULTS MAY VARY MATERIALLY FROM THOSE DESCRIBED IN THE FORWARD-LOOKING STATEMENTS.