Geochemistry and sedimentary provenance of the Upper Cretaceous Uberaba Formation (Southeastern Triângulo Mineiro, MG, Brazil)

Abstract

RESUMO: A Formação Uberaba, de idade campaniana e ocorrência restrita à região da cidade homônima, é composta de arenitos líticos e conglomerados de cor esverdeada, com possível contribuição vulcanoclástica. Nessa unidade ocorrem minerais pesados como ilmenita ABSTRACT:The campanian Uberaba Formation, which crops out around the homonymous town, is composed of greenish lithic sandstones and conglomerates with possible volcanoclastic contribution. In this unit, heavy minerals such as ilmenite, garnet, perovskite and magnetite, besides clinopyroxene, plagioclase, quartz, calcite and apatite, are found. The Uberaba Formation geochemistry is marked by high grades of Ba, Ta, La, Nb and Th, with flat (no Eu anomaly) and highly fractionated (La N /Yb N = ca. 128) chondrite-normalized rare earth elements. Mineral chemistry analyses of detrital garnets from the Uberaba Formation indicate the predominance of chorlomite with an affinity to crustal garnets (G3). The sedimentary provenance of the Uberaba Formation corresponds to a mixing of materials from the alkaline districts of the Alto Paranaíba and from the erosion of the Serra Geral Formation and the Canastra and Araxá groups. Diamond-producing conglomerates which crop out nearby, in Romaria, were considered by some authors as correlated to the Uberaba Formation. However, the composition of garnets recovered from those conglomerates is different, plotting in the field of mantle garnets (G9/G10). We consider, then, that those units are not correlated, and that the Uberaba Formation is not a possible source for the alluvial diamonds found in the homonymous river.

The Buffer Capacity of Riparian Vegetation to Control Water Quality in Anthropogenic Catchments from a Legally Protected Area: A Critical View over the Brazilian New Forest Code

“…The Uberaba Formation is made up of Cenozoic sediments, with a predominance of sedimentary rocks with volcaniclastic contribution, and overlays the Serra Geral Formation along an erosive contact. The upper contact with the Marília Formation is also considered abrupt, being marked by a silexite level and a conglomerate rich in quartz grains cemented by calcite [27].…”

A Regression Model of Stream Water Quality Based on Interactions between Landscape Composition and Riparian Buffer Width in Small Catchments

“…The studies mentioned in the previous paragraph link stream water quality variations to changes in buffer strip width and(or) landscape composition, acting independently as main effects, but fail to address potential joint effects. However, interactions among main effects are widely discussed in the scientific literature about regression models [38][39][40], and can play a role in the context of water quality assessments and their correlation with multi-scale factors. For example, stream water quality could be improved with narrower buffer strips if an enhanced self-purification of runoff was accomplished within a rural catchment by a large proportion of forest areas relative to agricultural areas.…”

Provenance Response to Rifting and Separation at the Jan Mayen Microcontinent Margin

“…Immediately above the unconformity with the underlying volcanic succession, a 2 m thick conglomerate unit is developed. This conglomerate contains a wide variety of alkaline igneous clasts unrecorded in the underlying Igtertiva Formation volcanic succession, which comprises the youngest part of the Blosseville Group and has been dated by the 40 Ar- 39 Ar method as 49.09 ± 0.48 Ma [23]. The Bopladsdalen Formation has a late Early Eocene age [29].…”