Climatic and geomorphologic cycles in a semiarid distributive fluvial system, Upper Cretaceous, Bauru Group, SE Brazil

Author(s)

Theodoro Soares, Marcus Vinicius ^[1] ; Basilici, Giorgio ^{[1, 2, 3]} ; Dal'Bo, Patrick Fuhr ^{[4, 2]} ; Marinho, Thiago da Silva ^[5] ; Mountney, Nigel Philip ^[2] ; Colombera, Luca ^[2] ; de Oliveira, Emerson Ferreira ^[1] ; Brito da Silva, Karla Evenny ^[1]

Affiliation

^[1] Univ Estadual Campinas, Inst Geosci, Dept Geol & Nat Resources, BR-13083870 Campinas, SP - Brazil

^[2] Univ Leeds, Sch Earth & Environm, Fluvial & Eolian Res Grp, Leeds LS2 9JT, W Yorkshire - England

^[3] Consejo Nacl Invest Cient & Tecn, Ctr Reg Invest Cient & Transferencia Tecnol, Buenos Aires, DF - Argentina

^[4] Univ Fed Rio de Janeiro, Inst Geosci, Dept Geol, Rio De Janeiro, RJ - Brazil

^[5] CCCP UFTM, Ctr Pesquisas Paleontol LI Price, BR-262, Km 784, BR-38001970 Uberaba, MG - Brazil

• Document type: Journal article
• Source: SEDIMENTARY GEOLOGY; v. 372, p. 75-95, OCT 2018.
• Web of Science Citations: 5

Abstract

Studies of distributive fluvial systems and their preserved successions envisage the distribution and orientation of architectural elements to be primarily controlled by channels radiating outward from fan apices, in many cases along an elongate basin margin. Conceptual models for such systems account for the downstream dynamics of the fluvial network, but with limited consideration of temporal geomorphic variations, resulting vertical organisation of architectural elements, or of the interplay of factors controlling system dynamics. To understand the external and internal architecture of distributive fluvial systems, and the factors that influence their sequential facies organisation, a sedimentary succession of the proximal portion of an Upper Cretaceous, semiarid, distributive fluvial system, located at the north-eastern margin of the Bauru Basin (Southeast Brazil), has been analysed in detail. Three fining- and thinning-upward fluvial sequences are identified, forming an interval separated at the top and the bottom by two palaeosol profiles. Each sequence is formed of channel and floodplain deposits. Two types of channel deposits are identified. One is composed of stacked sets of small-scale dune deposits, suggesting perennial and steady fluvial regime, associated with more humid climate periods. The other is composed of largescale sets indicative of flattened dunes associated with unsteady and fast-changing fluvial flow, formed in quasi supercritical flow regime conditions, associated with drier climate periods. The vertical alternation of these two types of channel deposits records the accumulation of a fluvial succession that responded to high-frequency, climate-induced cyclic change in boundary conditions. Two palaeosol profiles, at the top and at the bottom of the succession, indicate temporary interruptions and cessation of the fluvial sedimentation, likely related to avulsion of the fluvial belt. Thus, the studied succession reveals high-frequency climate-induced allogenic sedimentary cycles that occur within a long-period autogenic geomorphologic-induced sedimentary cycle. This work suggests that the internal architecture of the channel deposits can be used as a climate proxy, and that climate and geomorphology act jointly as notable factors to control the vertical organisation of distributive fluvial systems. (C) 2018 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 12/23209-0 - Sediments and palaeosols of Cretaceous desert depositional systems (Bauru Group, SE of Brazil, and Los Llanos formation, W of Argentina): proxies for palaeoenvironmental interpretation and stratigraphic benefits
• Grantee: Giorgio Basilici
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/06968-5 - Depositional architecture and dynamics of semiarid fluvial systems: the Bauru Group in the Triangulo Mineiro region (Upper Cretaceous)
• Grantee: Marcus Vinícius Theodoro Soares
• Support Opportunities: Scholarships in Brazil - Master