Meteoritics & Planetary Science 41, Nr 2, 237–246 (2006) Abstract available online at http://meteoritics.org 237 © The Meteoritical Society, 2006. Printed in USA. Investigation of Shuttle Radar Topography Mission data of the possible impact structure at Serra da Cangalha, Brazil Wolf U. REIMOLD 1* , Gordon R. J. COOPER 1 , Rafael ROMANO 2 , Duncan R. COWAN 3 , and Christian KOEBERL 4 1 Humboldt-Universit‰t zu Berlin, Museum f¸r Naturkunde, Institut für Mineralogie, D-10115 Berlin, Germany 2 Department of Geology, Federal University of Ouro Preto, Ouro Preto, Brazil 3 Cowan Geodata Services, 12 Edna Road, Dalkeith, Western Australia, Australia 4 Department of Geological Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria * Corresponding author. E-mail: uwe.reimold@museum.hu-berlin.de (Received 24 February 2005; revision accepted 18 September 2005) Abstract–The Serra da Cangalha crater structure in northeast Brazil, ∼13 km in diameter, has long been widely considered to be a confirmed impact structure, based on reports of shatter cone findings. Only very limited field work has been carried out at this crater structure. Landsat Thematic Mapper (TM) and Shuttle Radar Topography Mission (SRTM) data sets for the region around this crater structure are compared here with regard to their suitability to determine first-order structural detail of impact crater structures. The SRTM data provide very detailed information regarding drainage patterns and topography. A pronounced central ring of up to 300 m elevation above the surrounding area, two comparatively subdued intermediate rings of 6 and 10.5 km diameter, respectively, and the broad, complex crater rim of up to >100 m elevation can be distinguished in the Serra da Cangalha data. The maximum cratering-related regional deformation (radial and concentric features) seems to be limited to a radial distance of 16–18 km from the center of the structure. A first comparison of macrostructural information from several impact structures with that from Serra da Cangalha does not yield firm trends, but the database is still very small at this stage. The varied nature of the target geology strongly influences the development of structural features in any impact event. INTRODUCTION AND BACKGROUND The Serra da Cangalha structure is centered at 8°05′S and 46°52′W in the extreme northeast of Tocantins state in Brazil (Fig. 1). Based on findings of shatter cones, it is widely held that Serra da Cangalha is indeed a confirmed impact structure (Dietz and French 1973; McHone 1979; Santos and McHone 1979; CrÛsta 1987, 2004), although bona fide microscopic evidence of shock metamorphism has never been reported (CrÛsta 2004). Past authors assigned a diameter of 12–13 km to the structure, which is comprised of several ring features. Most prominent of these is a 3 km (5 km, according to De Cicco and Zucolotto 2002) inner circular ring of mountains 250–300 m high that lends this structure an appearance similar to that of the Gosses Bluff structure of Australia, which has a 4.5 km inner ring and a subdued outer rim feature at 24 km diameter (Milton et al. 1996). Similar to Gosses Bluff’s inner ring structure and that of the Libyan impact crater Oasis (Koeberl et al. 2005a), the inner ring at Serra da Cangalha is thought to represent the differentially eroded remnant of a lithologically diverse central uplift feature formed from a layered sequence of target rocks. The Serra da Cangalha structure was formed in the intracratonic ParnaÌba basin (formerly known as the Maranhão basin). The basin stratigraphy involves Upper Silurian to Cretaceous sedimentary rocks. The geology of the region and the structure was reviewed by CrÛsta (1982, 1987, and references therein). The strata within the structure include upper Permian sandstones of the Pedra de Fogo Formation, Permian/Carboniferous sandstones of the 323–290 Ma PiauÌ Formation and the 354–323 Ma Poti Formation, as well as dark shales of the Upper Devonian Long· Formation. The structure is surrounded by tabular outliers (mesas) of Triassic sandstones of the SambaÌba Formation. In the center of the structure, these strata are intensely deformed and display vertical dips (CrÛsta 1982) (presumably on bedding surfaces). On the basis of stratigraphic drilling in the region by the Geological Survey of Brazil, the original stratigraphic depth of the strata now exposed in the center of the impact structure is estimated between 100 and 1300 m below surface, which