Late Jurassic paleoclimate of Central Africa Timothy S. Myers ⁎, Neil J. Tabor, Louis L. Jacobs Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX 75275, United States abstract article info Article history: Received 22 September 2010 Received in revised form 27 July 2011 Accepted 26 August 2011 Available online 3 September 2011 Keywords: Congo Basin Stanleyville Group Paleosols Paleoclimate Stable isotopes Paleopedology and geochemical analysis of Upper Jurassic deposits in the Stanleyville Group of Central Africa indicate harsh Late Jurassic paleoclimates in the interior of Gondwana. Subsurface samples collected from the Samba borehole near the center of the Congo Basin show only weak morphological evidence of pedogenesis, but are characterized by an abundance of shrink-swell (vertic) features and rare calcium carbonate nodules, indicating seasonal variations in moisture availability and net soil moisture deficiency, respectively. X-ray dif- fraction analysis of paleosol matrix material reveals the presence of analcime and the clay mineral palygors- kite, strong indicators of hot, arid climatic conditions. The δ 18 O and δD values of clay minerals from paleosol profiles range from +22.3‰ to +25.4‰ and −44.4‰ to −39.6‰ SMOW, respectively, and correspond to crystallization temperatures between 25 °C and 40 °C. These crystallization temperatures compare favorably with austral summer surface temperature estimates for Central Africa that result from Late Jurassic global circulation models. Calculations of soil CO 2 production using the δ 13 C values of pedogenic carbonates and plant-derived organic matter produce lower CO 2 production estimates for the Stanleyville Group relative to the roughly contemporary Morrison Formation of the western U.S. These low soil CO 2 production estimates provide further support for arid Late Jurassic climate conditions in the Congo Basin. The paleoclimatic condi- tions inferred here from the Stanleyville Group are similar to those reconstructed from other Upper Jurassic African continental localities between 5°S and 20°S paleolatitude. However, penecontemporaneous terrestrial coastal sites within this latitudinal belt of Gondwana retain evidence of generally wetter conditions, suggesting that those regions may have received more rainfall than the continental interior. The paleoclimatic setting reconstructed here from geologic indicators and geochemical proxies suggests that general circulation models accurately predict unique paleoenvironmental conditions that lack modern analogs. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The latter half of the Jurassic Period was a time of significant paleo- geographic change as fragmentation of Pangea progressed and the in- cipient North Atlantic developed between North America and Eurasia (Uchupi, 1988; Smith et al., 1994; Golonka et al., 1996). These tectonic rearrangements brought about major changes in both climate and sea level (Parrish, 1993; Hallam, 2001). Global datasets of paleoclimate in- dicators suggest that low-latitude Late Jurassic environments were arid and tropical ever-wet conditions were absent (Rees et al., 2000). During the Late Jurassic, the African portion of Gondwana straddled the equator (Smith et al., 1994), providing a large area for development of low-latitude continental environments. Some of the Late Jurassic ter- restrial ecosystems that developed in eastern Africa boasted diverse faunas that rivaled those of contemporary Europe and North America (Goodwin et al., 1999; Aberhan et al., 2002), but data from this time pe- riod are lacking for much of the rest of the continent. Despite the fact that several east African localities have provided a wealth of vertebrate fossil material (Raath and McIntosh, 1987; Goodwin et al., 1999; Aberhan et al., 2002), Upper Jurassic continen- tal deposits compose only a small portion of the present surficial ge- ology of Africa, and little effort has been devoted to the study of paleoclimatic data recorded in these rocks. Paleoclimate interpreta- tions made from African Upper Jurassic strata are typically restricted to general comments on the presence of climatically-sensitive sedi- mentary indicators, presented as background information in studies of vertebrate faunas and depositional environments (e.g., Assefa, 1991; Aberhan et al., 2002). Even less is known about the terrestrial environments that developed in the interior of the African continent. The Upper Jurassic–Lower Cretaceous Stanleyville Group of the Congo Basin presents a unique opportunity to study the paleoclimatic condi- tions of low-latitude, Late Jurassic terrestrial environments deep in the interior of Gondwana. This study evaluates paleoclimatic conditions during deposition of the Stanleyville Group using paleopedological, mineralogical, and geochemical data. Examination of climatically-sensitive paleosol features and mineralogical composition yields information about relative amounts of precipitation and patterns of annual rainfall dis- tribution, while stable isotope analysis of clay minerals provides Palaeogeography, Palaeoclimatology, Palaeoecology 311 (2011) 111–125 ⁎ Corresponding author. Tel.: + 1 214 768 1751; fax: + 1 214 768 2701. E-mail address: smyers@smu.edu (T.S. Myers). 0031-0182/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2011.08.013 Contents lists available at SciVerse ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo