Idades K-Ar de rochas alcalinas do Brasil meridional e Paraguai oriental: compilação e adaptação às novas constantes de decaimento

Abstract

menç;oespedal a dataçfles Rb/Sr realizadils por KAW ASHITA et aI. (198l1),emalllOstrasdoMaciço de Poços de Caldas. Asanál1sesefetuadasnoCentrodePesquisasGeoctonol ógicasdoIG-USP(CPGeo),aparecem relacicnadasnaTabela 1 ccwnasiglaSPl<. Ase9-Jit , l1stam-seonoJmerodecaf1l)O,omaterlal NossosagradecimentossaoelltensivosàsEq:>resasr-u::learesBrasilelras(~EBRAS),NI pessoa de Jo~o Hilário Javaronl, pOr permitir a pJJlicaç~o dos dados das anostras de Poços de Caldas,depre rtlloRAA. Parte do trabalho de cQt!Clilaçao foi realizada no escopo dos audlios fornecidos pelo Cfo.PQ (processo 4Q7.383/87) e pela fIJ\EP (convênloFIJ\EP-USP, 42.86.0491.00, coordenadorH.H .G.J. UIbrich) .

New age determinations for the Banhadão and Itapirapuã complexes in the Ribeira Valley, southern Brazil

“…The radiometric ages of the alkaline rocks from Southern Brazil, mostly determined in the past by the K-Ar method (values recalculated by Sonoki & Garda 1988), allowed Ulbrich and Gomes (1981) to draw attention to the wide age interval of 40 to 240 Ma showed by the numerous occurrences, with peaks of higher concentration of values clearly distinguished in the histogram. Revising the whole set of data available and working only with the more precise and reliable analytical results, Ulbrich et al (1990) defined some age clusters, also referred to as chronogroups, that would correspond to the main peaks of alkaline magmatic activity in the entire region.…”

“…Other indications: I, Basement; II, Paraná Basin; III, Flood Basalts. Amaral et al 1967, Sonoki & Garda 1988b: CG, unpublished data;c: Ruberti 1984;d: Ruberti et al 1997;e: Gomes & Cordani 1965;f: Amaral 1978;g: Roden et al 1985;h: Chmyz et al 2017;i: Almeida et al 2017;j: Born 1971;k: Machado Jr. 2000;l: Cordani & Hasui 1968;m: Spinelli & Gomes 2008;n: Siga Jr. et al 2007). later, by Ruberti (1984) and Ruberti and Gomes (1984), who described the presence of a phlogopite melteigite body at the central-eastern portion of the complex and of a pipe-like, well-defined late body of nepheline syenites at the western section. These latter rocks are clearly characterized by the presence of centimetric to decimetric, rounded to subrounded or even to polygonal structures (up to 40 vol.%) of alkali feldspar-nepheline intergrowths, along with kalsilite segregations, generally looking like pseudoleucite crystals (Comin-Chiaramonti et al 2008, Ruberti et al 2012.…”

“…These ages were recalculated later by Sonoki and Garda (1988) using the new decayment constants as proposed by Steiger and Jäger (1977).…”

Freshwater Decapoda trace fossils in floodplain paleosols of Marilia Formation in Minas Gerais State (SE Brazil)

“…Based on the integration of paleontological data (Gobbo-Rodrigues, 2001;Dias-Brito et al, 2001;Santucci & Bertini, 2001;Martinelli et al, 2011;Fragoso et al, 2013), stratigraphic information (Batezelli, 2015), as well as correlations with tectonic and magmatic events (Amaral et al, 1967;Hasui & Cordani, 1968;Sonoki & Garda, 1988;Machado Junior, 1992) that occurred in the northern and northeastern portions of the Bauru Basin, a Maastrichtian age is admitted for the Marília Formation. The outcrops of the Marilia Formation are densely bioturbated and cemented, resulting in the almost total obliteration of many sedimentary structures.…”

Comparação Da Dinâmica Evolutiva, a Longo E Curto Prazo, Entre O Planalto De Poços De Caldas E O Planalto De São Pedro De Caldas

“…al., 1979). Com importância destacada no relevo regional, sua história inicia-se com a intrusão de rochas félsicas em aproximadamente 89 Ma, acarretando em domeamento da região, e estende-se até cerca de 54 MA (SONOKI & GARDA 1988, ULBRICH et al, 2002, através de episódios de vulcanismo, abatimento do conduto vulcânico e estruturação da caldeira (ELLERT, 1959).…”