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.
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.
Filho W.S.,Instituto Geologico |
Sapiensa Almeida L.H.,University of Sao Paulo |
Boggiani P.C.,University of Sao Paulo |
Karmann I.,University of Sao Paulo
Carbonates and Evaporites | Year: 2012
Active tufas in the form of waterfalls and dams occur along drainage channels in the Serra do André Lopes region (State of São Paulo, southeastern Brazil) and are associated with the karst system that developed on a dolomitic plateau with a superhumid subtropical climate. The predominance of autogenic waters enables the groundwater to become enriched in calcium carbonate, with low terrigenous sediment content. The tufas that were studied are composed of calcite and have high calcium contents and low magnesium contents. Eroded tufa beds that originate from changes in the position of fluvial channels or river flow rates also occur in this region. In the Sapatú deposit, phytohermal tufas with complex morphologies are arranged in levels constituting various temporally repeated sequences that were deposited between 10,570 and 4,972 cal years BP. In the Frias deposit, distal fluvial deposits of tufa are massive with a relatively greater quantity of terrigenous material and show evidence of dissolution and reprecipitation. The base of this deposit is composed of a cemented breccia dated at 25,390 years BP, which is younger than the overlying tufas ([42,000 years BP). In the two deposits, the levels of terrigenous sediments (quartz sand and lithic pebbles) and terrestrial gastropod shells are interpreted as phases of increased flow rate of rivers during intervals of higher rainfall. © 2012 Springer-Verlag.
Pennsylvanian palynofloras from the Itu rhythmites (Itararé Subgroup, Paraná Basin) in São Paulo State, Brazil [Palynoflores pennsylvaniennes des rythmites de Itu (Sous-groupe Itararé, Bassin du Paraná), État de São Paulo, Brésil]
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.
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.