Pre- and post-Marinoan carbonate facies of the Democratic Republic of the Congo: Glacially- or tectonically-influenced deep-water sediments? Franck Delpomdor a, ⁎, Nicholas Eyles b , Luc Tack c , Alain Préat a a Biogeochemistry and Modeling of the Earth System, Université libre de Bruxelles, Brussels, 1050, Belgium b Physical and Environmental Sciences, University of Toronto, Scarborough, Ontario, M1C 1A4, Canada c Royal Museum for Central Africa, Tervuren, 3080, Belgium abstract article info Article history: Received 24 February 2016 Received in revised form 8 June 2016 Accepted 9 June 2016 Available online 11 June 2016 The upper carbonate-rich parts of the West Congo Supergroup (~1000–560 Ma) from the Democratic Republic of the Congo have hitherto been considered as a record of abrupt eustatic and climatic events accompanying glaciation and deglaciation of a Snowball Earth-type Marinoan ice age that was of global extent. These strata have however never been investigated in detail. Results of new sedimentological work at key outcrops over a 1300 km outcrop belt show that pre- and post-Marinoan carbonates are respectively, storm-influenced sediments deposited principally in a mid/outer-ramp setting, and deep-water slope carbonates (calicturbidites) representing a lobe-fringe or levee-overbank setting. The Upper Diamictite Formation held previously by some to be a subglacial tillite, comprises gravity flows (debrites) deposited in deep water below wave base along the unstable margins of a carbonate ramp. A direct glacial influence on sedimentation for diamictites or any accom- panying facies cannot be readily identified. Sedimentary facies reported here primarily record the presence of deep-water submarine to alluvial fan systems related to extensional tectonic processes of the central-southern Macaúbas Basin (now located in Brazil) between 700 Ma and 660 Ma followed by the 630-Ma onset of the pre-collisional magmatic arc in the Araçuaí-West Congo Orogen. No extreme short-lived climatic or eustatic events of a Snowball Earth-type ice age are recorded in the studied succession, which primarily reflects long- term overriding regional tectonic controls resulting in diachronous sedimentation along the western margin of the Congo Craton. © 2016 Elsevier B.V. All rights reserved. Keywords: Neoproterozoic Snowball Earth Debrites Deep-water carbonates Diamictite Tectonics 1. Introduction The Neoproterozoic Era (~1000–540 Ma) has been argued by some to be characterized by several catastrophic Snowball Earth-type ice ages involving short-lived global climate and eustatic events (Kirschvink, 1992; Hoffman et al., 1998; Hoffman and Schrag, 2002). The model postulates extremely low global temperatures (-50 °C) dur- ing several long-lived Neoproterozoic glacioeras (~770–735 Ma Kaigas, ~715–680 Ma Sturtian, ~660–635 Marinoan, and ~585–582 Ma Gaskiers events). Each event has been argued to involve the growth of large continental-scale ice sheets at sea level in areas near the equator, and a thick ice cover on the world's oceans. Based on the commonly considerable thickness of Neoproterozoic diamictites (to 1 km), lateral extent and in some cases, diagnostic glaciogenic features, such as subglacially striated pavements, facetted and striated clasts, ice-rafted dropstones and far-travelled extrabasinal clast assemblages (Boulton, 1978; Etienne et al., 2007; Arnaud and Etienne, 2011; Arnaud, 2012 and references therein), diamictites have at one time or another been reported as terrestrial glacial or cold climate deposits left by the melting of continental ice sheets (‘tillites’). The presence in places of rocks interpreted as glaciogenic in origin with an overlying dolomite unit has been described as evidence of abrupt warming related to an increase of atmospheric carbon dioxide due to volcanic degassing. However, other work has cautioned that thick diamictites more often than not lack convincing glacial indicators and are deep marine deposits intimately associated with thick (~1 km) turbidite successions. These facies together form distinct tectonostratigraphic successions that were deposited in evolving tectonically-active rift basins as Rodinia broke apart. Diamictites often many hundreds of metres in thickness, are commonly amalgamated debrites recording repeated reworking and often mixing of gravelly and muddy coastal facies into deep water, thereby demanding caution in inferring direct glacially- controlled climatic and eustatic interpretations from such succes- sions (see Eyles and Januszczak, 2004a, 2004b, 2007; Arnaud and Eyles, 2002, 2006; van Loon, 2008; Direen and Jago, 2008; Evans and Raub, 2011; Arnaud, 2012; Carto and Eyles, 2012 and discussion therein). Varying degrees of glacial influence have certainly been identified but point to regional, not global, ice covers strongly Palaeogeography, Palaeoclimatology, Palaeoecology 457 (2016) 144–157 ⁎ Corresponding author at: Illinois State Geological Survey, University of Illinois, Champaign, IL 61820, United States. E-mail address: delpomdor.franck@gmail.com (F. Delpomdor). Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo