Reconstructing the Evolution of Cave Systems As a Key to Understanding the Taphonomy of Fossil Accumulations
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Quaternary International 339-340 (2014) 25e40 Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint Reconstructing the evolution of cave systems as a key to understanding the taphonomy of fossil accumulations: The case of Urs¸ ilor Cave (Western Carpathians, Romania) Silviu Constantin a,*, Marius Robu b, Cristian-Mihai Munteanu b, Alexandru Petculescu b, Marius Vlaicu b, Ionut¸ Mirea a, Marius Kenesz c, Virgil Dragus ¸ina, Dirk Hoffmann d, Valentina Anechitei e,f, Alida Timar-Gabor e,f, Relu-Dumitru Roban g, Cristian G. Panaiotu g a The “Emil Racovit¸ a” Institute of Speleology, Center for Geochronology and Paleoclimate, str. Frumoasa 31, 010986 Bucharest, Romania b The “Emil Racovit¸ a” Institute of Speleology, Calea 13 Septembrie, 13, 050711 Bucharest, Romania c The “Emil Racovit¸ a” Institute of Speleology, Cluj Branch, str. Clinicilor 5, 400006 Cluj-Napoca, Romania d CENIEH, Paseo Sierra de Atapuerca s/n, 09002 Burgos, Spain e Faculty of Environmental Science and Engineering, Babes¸ -Bolyai University, Fântânele 30, 400294 Cluj Napoca, Romania f Interdisciplinary Research Institute on Bio-Nano-Science, Babes¸ -Bolyai University, Treboniu Laurean 42, 400271 Cluj-Napoca, Romania g Faculty of Geology and Geophysics, University of Bucharest, N. Bâlcescu 1, 010041 Bucharest, Romania article info abstract Article history: The Urs¸ ilor Cave (NW Romania) is a famous cave bear paleontological site hosting an important Late Available online 5 November 2013 Pleistocene faunal assemblage and subject to systematic excavation works. To better understand the origin of fossil assemblages, the sedimentary history of the cave must be reconstructed. We conducted a series of investigations on various cave deposits which included sedimentology and grain-size analyses, U-series dating of speleothems, OSL dating of sediments, and AMS radiocarbon dating of fossil remains. The results allowed for the identification of several major chronological controls for the evolution of the cave during the last 300,000 years. Five evolutionary stages or key-moments were dated, and a tentative speleogenetic scenario is presented. The combined numerical dates and sedimentological study show that the evolution of the cave was more complex than previously thought. In particular, the fossil accumulation was related to a succession of rapid flooding events at w47e40 ka. Alternating deposi- tional and erosional phases have occurred since at least 210 ka complicating the sediment structures. The results suggest that the upper and lower levels of the cave may have been functioned occasionally as hydrologically separated karst systems and that the animal populations from what is now a single cave system may not necessarily be synchronous. This case study shows that reconstructing sedimentary history of a given cave is crucial for the correct understanding of its thanatocenosis. Ó 2013 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction hydraulic regimes (Sasowsky and Mylroie, 2004). The associations of fossil remains preserved in caves, especially those of micro- Cave deposits are largely recognized as holding the potential of mammals, have been long considered as a paleoclimate proxy. valuable palaeoenvironmental and paleoclimatic archives (see, for Moldovan et al. (2011) have shown that even invertebrate fossil example, Ford and Williams, 2007; White, 2007). Speleothems are associations from cave sediments may be used as another paleo- currently considered as one of the most reliable cave archives for environmental proxy. reconstructing paleoclimate evolution at regional scale (Fairchild The advance of direct and indirect dating techniques (e.g. and Baker, 2012). Fluviatile or lacustrine sediments from caves Couchoud, 2006; Grün, 2006; Berger et al., 2008) has allowed for a are also physical and chemical recorders of past climate and better understanding of both the timing and the palae- oenvironmental significance of large fossil accumulations and/or archaeological sites. However, especially in deep-cave settings, a key-requirement for understanding the taphonomy of a paleonto- * Corresponding author. logical deposits is the correct interpretation of the evolution of the E-mail address: [email protected] (S. Constantin). given cave system. Often (e.g. Zupan Hajna et al., 2008; Trinkaus 1040-6182/$ e see front matter Ó 2013 Elsevier Ltd and INQUA. All rights reserved. http://dx.doi.org/10.1016/j.quaint.2013.10.012 26 S. Constantin et al. / Quaternary International 339-340 (2014) 25e40 et al., 2013), this can only be achieved by the combined study of a (Fig. S1) that leads to a small chamber (the Excavation Chamber) wide range of cave archives and/or the analysis of coeval proxies. and the Scientific Reserve. The paleontological excavation of the sediment deposit from the The Scientific Reserve is the lower level of Urs¸ilorCave(w500 m in Scientific Reserve in Urs¸ ilor (¼Bears)Cave(Robu et al., 2011) has length) and includes a generally large horizontal passage (10 Â 15 m), revealed the presence of an extensive bone bed including mostly with several small side-passages and fossil meanders (Fig. S2). A small cave bear remains but also two cave lions and at least one hyaena stream (1e10 l/s) flows through the lower level and sinks into an and one mustelid. The taphonomic analysis has revealed that the impenetrable sump in the Excavation Chamber. Along the lower vertebrate remains may have been accumulated via multiple passage, the stream has deposited alluvial sediments consisting of mechanisms such as pitfall entrapment, natural death (including fine sands, silts, and clays which often support stalagmite formations drowning) or fluvial transport. As direct radiocarbon dating has on their top. Currently the stream meanders through w0.5e3 m-high yielded results that are close to or exceed the limits of the method, alluvial terraces. In the Excavation Chamber, it sinks and flows the dating of complementary cave deposits and the understanding through an accumulation of sediments that exceeds 200 m3 of a mix of the speleogenetic scenario are crucial for taphonomical of sandy-clayish alluvia and fossil bone beds. interpretations. Both cave levels host important cave bear bone assemblages With only a few exceptions (Constantin, 2003; Petculescu and (both on the surface and within the sediment, scattered or fully Murariu, 2009; Häuselmann et al., 2010; Trinkaus et al., 2013) articulated specimens) and cave bear ichnofabrics (nests, scratch most studies on the evolution of karst systems from the Romanian marks, footprints and fur imprints). However, most articulated Carpathians rely only on stratigraphical and geomorphological skeletons and ichnofabrics are found in the Lower Level whereas in evidence. Urs¸ ilor Cave is no exception, with the earlier attempts to the Upper Level the fossil remains are more scattered and/or reconstruct the evolution of the cave and the sedimentation covered by massive speleothem formations. mechanisms and chronology (Hadnagy, 1977; Terzea, 1978, 1989; The genesis of the cave system has been largely interpreted by Valenas ¸ , 1979; Jurcsák et al., 1981) relying mostly on the analysis corroborating observations on the overall cave morphology and of the mineralogy of sediments, cave morphology, and a partial correlations of the different cave levels with the local river terraces paleontological record. (Valenas ¸ , 1979; Rusu, 1981; Rusu and Racovit¸ a, 1981). In broad This study focuses on the establishment of a chronological and terms, the evolution of the cave was thought to include the evolutionary framework for the Urs¸ ilor Cave in the last w300,000 following stages: years. It integrates the study of relevant cave deposits (cave sedi- ments, speleothems, and fossil bones) which were directly or (1) an initial karst drainage towards the Craiasa Valley led to indirectly dated by means of radiocarbon, U-series, and optically the formation of the Upper Level passages. This stage in- stimulated luminescence (OSL). It also integrates new, detailed, cludes successive abandonments of older passages, in pace geomorphological and topographical surveys of the cave that are with the deepening of the base level. The Twisted Passage relevant to its speleogenesis. The aim of the study was to provide a was abandoned in favour of a new resurgence via the solid chronological and paleoevolutive basis for the taphonomical Candlesticks Passage which was, in turn, abandoned for a interpretation of the fossil accumulation from the Scientific Reserve new drainage via the Access Passage. of Urs¸ ilor Cave. (2) the capture of the subterranean stream towards the end of the “Emil Racovit¸ a” Passage. A new drainage was established to- 2. Background wards the Pes¸teradelaChis¸cau, a small (148 m) resurgence cave located w40 m below the current entrance of Urs¸ilor Urs¸ ilor Cave is located on the western slope of the Apuseni Cave (Figs. 1 and 2). The greatest part of the passages between Mountains (Western Carpathians, Romania), on the left side of the the sink and Pes¸ tera de la Chis¸cau are impenetrable and Craiasa Valley, at 491 m a.s.l (Fig. 1). The cave was discovered in thought to be generally small in size. This may have caused 1975 by blasting in a local marble quarry. Owing to both its rich and periodic accumulations of water upstream the sink and the complex Upper Pleistocene thanatocenosis, and the abundance of deposition of alluvial material throughout the Lower Level. speleothems,