LATE CRETACEOUS STRATIGRAPHY OF THE SOUTHEASTERN CHACO - PARANÁ BASIN (“NORTE BASIN” - URUGUAY): THE MAASTRICHTIAN AGE OF THE CALCRETIZATION PROCESS

Gerardo Veroslavsky,Natalie Aubet,Sergio A Martínez,Larry M Heaman,Valeria Mesa,Fernanda Cabrera

doi:10.5016/geociencias.v38i2.13779

Gerardo Veroslavsky, Natalie Aubet + Show 4 more

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https://doi.org/10.5016/geociencias.v38i2.13779

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Abstract

In the last 40 years, successive revisions have been introduced to the lithostratigraphy of the Late Cretaceous of the Norte Basin, whose record is formed by predominantly siliciclastic continental fossiliferous sedimentary rocks. A factor that contributed to the terminology proliferation was the misplaced importance attributed to the epigenetic processes and products (calcretes and ferricretes, occasionally fossiliferous) affecting those siliciclastic rocks. Based on field work and lithological logs from a number of key areas, the validity of the original stratigraphic column showing, from base to top, the Guichón, Mercedes, Asencio and Queguay formations is supported. For those particular units, the lithostratigraphic scope given by the original definitions is correct and, with minimum adjustments, they should be restored for their practical usefulness as geological mapping units. An evolutionary scheme for the Late Cretaceous of the Norte Basin is herein presented, with the aim of contributing to a greater understanding of the succession of sedimentary and epigenetic processes. A Maastrichtian age is proposed for the carbonatic cementation and/or substitution that affected the Mercedes and Asencio formations, thus originating the Queguay Formation, based on absolute age of the calcite cement (~ 72 Ma; U-Pb), paleontological data, and the correlation established with similar events recorded in the Marília Formation on the Bauru Basin (Brazil).

Highlights

Geological Setting Methodology ResultsStratigraphic section The Queguay quarry sectionABSTRACT - In the last 40 years, successive revisions have been introduced to the lithostratigraphy of the Late Cretaceous of the Norte Basin, whose record is formed by predominantly siliciclastic continental fossiliferous sedimentary rocks
Based on extensive field work in key areas, fundamental contributions on paleontological aspects of the Queguay Formation, and the results of experimental radiometric (U-Pb) dating of early diagenetic carbonate phases, in this paper we review the lithostratigraphy of the Late Cretaceous in the Norte Basin of Uruguay, within the framework of the paleogeographic context given by the Bauru Basin and the Argentinean Mesopotamia
The results firstly show the regional stratigraphic sections of the Norte Basin in general and, secondly, focus on the key section of the Queguay quarry, representative of the Queguay Formation type area

Summary

Introduction

Geological Setting Methodology ResultsStratigraphic section The Queguay quarry sectionABSTRACT - In the last 40 years, successive revisions have been introduced to the lithostratigraphy of the Late Cretaceous of the Norte Basin, whose record is formed by predominantly siliciclastic continental fossiliferous sedimentary rocks. Based on field work and lithological logs from a number of key areas, the validity of the original stratigraphic column showing, from base to top, the Guichón, Mercedes, Asencio and Queguay formations is supported. During the Late Cretaceous, the new tectonic and depositional scenarios favored the accumulation of continental sediments unconformably overlying the Early Cretaceous basaltic areas formed within the old domains of the Paleozoic Paraná and Chaco-Paraná basins (Figure 1). This situation promoted the development of clastic and fossiliferous alluvial, fluvial, lacustrine, and aeolian depositional systems (Fernandes & Coimbra, 1996), greatly influenced by a regional west-southwest trending flow that transported sediments down paleoslope from the Paleo Paraná-Plata systems to the Salado and Punta del Este basins (Potter, 1997). A considerable number of scientific contributions discuss the pedogenetic/diagenetic schemes concerning the formation of calcretes in the Mercedes, Asencio and Queguay formations (Tófalo, 1986; Veroslavsky & Martínez, 1996; Veroslavsky et al, 1997; Tófalo et al, 2001; Tófalo & Morras, 2009; Tófalo & Pazos, 2010; Alonso-Zarza et al, 2012; Martínez et al, 2015; Cabrera et al, 2018)

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