https://doi.org/10.1130/G46740.1 Manuscript received 27 November 2018 Revised manuscript received 8 September 2019 Manuscript accepted 10 September 2019 © 2019 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana Neil Patrick Griffis1,2*, Isabel Patricia Montañez1, Roland Mundil2, Jon Richey1, John Isbell3, Nick Fedorchuk3, Bastien Linol4, Roberto Iannuzzi5, Fernando Vesely6, Thammy Mottin6, Eduardo da Rosa6, Brenhin Keller2 and Qing-Zhu Yin1 1 Department of Earth and Planetary Sciences, University of California, Davis, California 95616, USA 2 Berkeley Geochronology Center, Berkeley, California 94709, USA 3 Department of Geosciences, University of Wisconsin, Milwaukee, Wisconsin 53211, USA 4 Department of Geosciences, Nelson Mandela University, Port Elizabeth 6019, South Africa 5 Departamento de Paleontologia e Estratigrafa, Universidade Federal Rio Grande do Sul, Porto Alegre, RS, 90040-060, Brazil 6 Departamento de Geologia, Universidade Federal do Paraná, Curitiba, PR, 80060-000, Brazil ABSTRACT and dynamics. Tectonic controls would have The demise of the Late Paleozoic Ice Age has been hypothesized as diachronous, occurring operated on 106 to 107 yr time scales and re- frst in western South America and progressing eastward across Africa and culminating in sulted in a diachronous glacial record across Australia over an ∼60 m.y. period, suggesting tectonic forcing mechanisms that operate on high-latitude Gondwana (Isbell et al., 2012; time scales of 106 yr or longer. We test this diachronous deglaciation hypothesis for south- Limarino et al., 2014). Late Paleozoic climate western and south-central Gondwana with new single crystal U-Pb zircon chemical abra- simulations, however, do not support a tectonic sion thermal ionizing mass spectrometry (CA-TIMS) ages from volcaniclastic deposits in the drift model for ice initiation thresholds (Lowry Paraná (Brazil) and Karoo (South Africa) Basins that span the terminal deglaciation through et al., 2014). Conversely, a CO2 driver would the early postglacial period. Intrabasinal stratigraphic correlations permitted by the new have operated on shorter time scales, analogous high-resolution radioisotope ages indicate that deglaciation across the S to SE Paraná Basin with the Cenozoic glaciation history of Antarc- was synchronous, with glaciation constrained to the Carboniferous. Cross-basin correlation tica (Miller et al., 2005). Notably, CO2-forced reveals two additional glacial-deglacial cycles in the Karoo Basin after the terminal degla- deglaciation (and associated base-level changes) ciation in the Paraná Basin. South African glaciations were penecontemporaneous (within would be expected to have been rapid (103 to U-Pb age uncertainties) with third-order sequence boundaries (i.e., inferred base-level falls) 105 yr) and thus broadly synchronous across in the Paraná Basin. Synchroneity between early Permian glacial-deglacial events in south- multiple basins. western to south-central Gondwana and pCO2 fuctuations suggest a primary CO2 control The precision and distribution of existing on ice thresholds. The occurrence of renewed glaciation in the Karoo Basin, after terminal U-Pb age constraints for ice-proximal deposits deglaciation in the Paraná Basin, refects the secondary infuences of regional paleogeogra- of southern Gondwana precludes evaluation of phy, topography, and moisture sources. the relative infuence of hypothesized glaciation- deglaciation drivers and their role in the ulti- INTRODUCTION marino et al., 2014) as well as tectonic controls mate turnover to a permanent greenhouse in the The Late Paleozoic Ice Age (LPIA), span- (Visser, 1997). Alternatively, CO2 forcing has middle Permian. Here we present a temporally ning 340–280 Ma, has produced the only known been hypothesized as the primary driver of the refned record of glaciation in southwestern to archive of a permanent icehouse-to-greenhouse repeated, discrete glaciations and intervening south-central Gondwana across the latest Car- turnover on a planet populated by complex ter- periods of diminished ice, and the ultimate turn- boniferous and early Permian, built using high- restrial ecosystems and metazoan life (Gastaldo over to permanent greenhouse conditions (Mon- precision, single-crystal zircon U-Pb chemical et al., 1996). The spatial and temporal distri- tañez et al., 2007, 2016). Although these two abrasion thermal ionizing mass spectrometry bution of continental ice throughout southern proposed forcing mechanisms (tectonic versus (CA-TIMS) dating of volcaniclastic deposits lo- Gondwana during the LPIA and its ultimate climate) for the late Paleozoic glaciation history cated within the earliest postglacial sediments demise have been attributed in large part to are interlinked through the infuence of large- of the Paraná Basin, Brazil, and two glacial- 7 8 the long-term (10 to 10 yr) drift of southern scale tectonics on CO2 sources (i.e., volcanism) deglacial cycles (deglaciation sequences DS III Gondwana away from the South Pole during and sinks and through atmospheric and ocean and DS IV) in the Karoo Basin, South Africa the Carboniferous–Permian (Crowell, 1983; Li- circulation (McKenzie et al., 2016; Montañez (Visser, 1997). The new chronostratigraphic et al., 2016), the two mechanisms differ in their framework is used to evaluate the synchroneity *E-mail: [email protected] temporal scales of infuence on ice distribution of ice loss across this region and to evaluate the CITATION: Griffs, N.P., et al., 2019, Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana: Geology, v. 47, p. XXX–XXX, https://doi.org/10.1130/G46740.1 Geological Society of America | GEOLOGY | Volume XX | Number XX | www.gsapubs.org 1 Downloaded from https://pubs.geoscienceworld.org/gsa/geology/article-pdf/doi/10.1130/G46740.1/4836971/g46740.pdf by Southern Connecticut State University user on 08 October 2019 base-level response in the Paraná Basin to the Paraná Basin occurs within the upper Taciba For- Two third-order depositional sequences, higher-latitude ice record (Karoo Basin) during mation (Itararé Group), composed of diamictite previously suggested to have been controlled the early Permian. and dropstone-poor mudstones (Fig. 1; Vesely by regional tectonic forcing (Holz et al., 2006), and Assine, 2004). The terrestrial and marginal occur in the latest Carboniferous through early GEOLOGIC SETTING, marine facies assemblage of the Guatá Group, Permian sedimentary record of the Paraná Ba- STRATIGRAPHY, AND EXISTING U-Pb which include the Rio Bonito and Palermo For- sin. The frst sequence boundary (SB-2 of Holz GEOCHRONOLOGY mations, overlay the Itararé Group and attain a et al. [2006]) separates deeper-water glacially The Paraná and Karoo Basins span a collec- maximum thickness of 300 m (Fig. 1; Rocha- infuenced diamictites and organic mudstones tive area of 2.3 × 106 km2 and were the largest Campos et al., 2008, Holz et al., 2010). In south- of the Taciba Formation from fuvial sandstones depocenters of LPIA sediment accumulation eastern Paraná Basin, the Rio Bonito Formation and coals of the Triunfo Member of the Rio Bo- in southwestern to south-central Gondwana is further divided into the Triunfo, Paraguaçú, nito Formation in the southeastern Paraná Basin (Fig. 1). The Paraná Basin, located between 40°S and Siderópolis Members (Schneider et al., (Fig. 1). In regions of the southern Paraná Basin, and 55°S during the earliest Permian (Franco 1974), which are not formally recognized in this sequence boundary locally separates crystal- et al., 2012; Domeier and Torsvik, 2014), re- the southern Paraná Basin. However, sequence line basement and fuvial sandstones (SB-1 + 2 cords an extensive record of paleo-glaciation boundaries SB-2 and SB-3, which bracket these of Holz et al. [2006]). In the southeastern Paraná within the Itararé Group (Rocha-Campos et al., members, are correlated between regions (Fig. 1; Basin, the fuvial sandstones of the Triunfo Mem- 2008). Record of the demise of glaciation in the Holz et al., 2006; Iannuzzi et al., 2010). ber transition into the offshore mudstones of the Figure 1. Stratigraphic columns of the core, outcrop, and mines for the southern and southeastern Paraná Basin, Brazil, and for the Karoo Basin, South Africa, calibrated by U-Pb zircon chemical abrasion thermal ionizing mass spectrometry (CA-TIMS) ages (see the Data Reposi- tory [see footnote 1]). Core HV-59 is located in the Candiota region of southern Brazil. The Karoo Basin section is modifed after Visser (1997). DS II–DS IV are deglaciation sequences correlated across the Karoo Basin (Visser, 1997). Stars indicate stratigraphic position of CA-TIMS samples (black—published values [Griffis et al., 2018]; red—new data presented in this study). Asterisks (*) on age markers 7 and 8 denote sample locations reported by Bangert et al. (1999) and resampled and dated in this study. Gray bars are correlated marine transgressions: T-CP—transgression, Carboniferous-Permian; T-P1—transgression, Permian 1 (296 Ma); T-P2—transgression, Permian 2 (282 Ma). Approxi- mate distances between regions are noted at top of fgures. SB—sequence boundaries and interpreted ages (Holz et al., 2006); Gp.—Group; Fm.—Formation; It.—Itararé Group; Tc.—Taciba Formation; PG—Paraguaçú Member; PL—Palermo Formation; PA—Prince