The Upper Jurassic Stanleyville Group of the eastern Congo Basin: An example of perennial lacustrine system Alexis Caillaud a, * , Christian Blanpied b , Damien Delvaux c a LOG, UMR CNRS 8187, Universit e de Lille, B^ at. SN5, 59655, Villeneuve d'Ascq Cedex, France b TOTAL SA EP/PN, 2 Place Jean Millier, La D efense 6, 92278, Paris La D efense Cedex, France c Royal Museum for Central Africa, Geodynamics and Mineral Resources, B-3080, Tervuren, Belgium article info Article history: Received 3 November 2016 Received in revised form 28 April 2017 Accepted 1 May 2017 Available online 3 May 2017 Keywords: Congo Basin Stanleyville Group Jurassic Lacustrine sedimentology Central Africa abstract The intracratonic Congo Basin, located in the Democratic Republic of Congo (DRC), is the largest sedi- mentary basin of Africa. The Jurassic strata outcrop along its eastern margin, south of Kisangani (formerly Stanleyville). In the last century, the Upper Jurassic Stanleyville Group was described as a lacustrine series containing a thin basal marine limestone designed as the “Lime Fine” beds. Since the proposal of this early model, the depositional environment of the Stanleyville Group, and especially the possible marine incursion, has been debated, but without re-examining the existing cores, outcrop samples and historical fossils from the type location near Kisangani that are available at the Royal Museum for Central Africa (MRAC/KMMA, Tervuren, Belgium). In order to refine the former sedimentology, a series of nine exploration cores drilled in the Kisangani sub-basin have been described. This study aims at integrating sedimentary facies in existing sedimentary models and to discuss the hypothesis of the presence of Kimmeridgian marine deposits along the Congo River near Kisangani, a region which lies in the middle of the African continent. Eight facies have been identified, which permit a reinterpretation of the deposi- tional environment and paleogeography of the Stanleyville Group. The base of the Stanleyville Group is interpreted to represent a conglomeratic fluvial succession, which filled an inherited Triassic paleo- topography. Above these conglomerates, a transition to a typically lacustrine system is interpreted, which includes: (1) a basal profundal, sublittoral (brown to dark fine-grained siltstones with microbial car- bonates, i.e., the “Lime Fine” beds) and littoral lacustrine series; covered by (2) a sublittoral to profundal interval (brown to dark organic-rich, fine-grained siltstones), which corresponds to the maximum extent of the paleo-lake; and, finally (3) a shallow lacustrine series (greenish calcareous siltstones and sand- stones with red siltstones). Unlike what has been proposed, the “Lime Fine” beds are interpreted herein to be of lacustrine origin, rather than representing a Kimmeridgian marine transgression. We conclude that a Jurassic marine transgression did not, in fact, occur in the eastern region of the Congo Basin. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Near the center of the African continent, the Congo Basin was probably initiated as an aborted rifted basin during the early Neoproterozoic (~1.0e0.9 Ga), and then it evolved into an intra- cratonic basin in the Phanerozoic (Kadima et al., 2011a). During the Mesozoic, continental conditions prevailed for most of this time; however, some workers have suggested that brief marine in- cursions during the deposition of the Upper Jurassic Stanleyville Group and Upper Cretaceous Kwango Group may have flooded the basin (Cahen, 1954, 1983). Moreover, due to its large size (about 1.2 million of km 2 ), the deposition of continental series in the Congo Basin was driven by geological processes other than those gov- erning the deposition of sediments in the surrounding Mesozoic to Tertiary rifts. For instance, a short marine incursion during the Kimmeridgian (~155 Ma) was proposed to have reached the area of Kisangani (former Stanleyville) from the Indian paleo-coast (Cahen, 1983). Indeed, a thin (43 cm thick) marker horizon of limestones, the “Lime Fine” beds (Cahen, 1983), is interpreted as a marine in- terval in the lacustrine Stanleyville Group. However, the marine origin of this marker horizon has never been questioned or tested (Saint Seine,1955; Saint Seine et Casier,1962; Taverne,1975; Cahen, 1983; Linol et al., 2015a) although it has been widely used as * Corresponding author. E-mail address: caillaud.alexis@gmail.com (A. Caillaud). Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci http://dx.doi.org/10.1016/j.jafrearsci.2017.05.002 1464-343X/© 2017 Elsevier Ltd. All rights reserved. Journal of African Earth Sciences 132 (2017) 80e98