Lithographus, an Abundant Arthropod Trackway from the Cretaceous Haenam Tracksite of Korea Nicholas J

This article was downloaded by: [Pukyong National University] On: 22 March 2012, At: 02:37 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Ichnos: An International Journal for Plant and Animal Traces Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gich20 Lithographus, an Abundant Arthropod Trackway from the Cretaceous Haenam Tracksite of Korea Nicholas J. Minter a , Martin G. Lockley b , Min Huh c , Koo-Geun Hwang c & Jeong Yul Kim d a Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada b Dinosaur Tracks Museum, University of Colorado, Denver, Colorado, USA c Faculty of Earth Systems and Environmental Sciences and Korea Dinosaur Research Center, Chonnam National University, Gwangju, Korea d Department of Earth Science Education, Korea National University of Education, Cheongwon, Korea Available online: 19 Mar 2012 To cite this article: Nicholas J. Minter, Martin G. Lockley, Min Huh, Koo-Geun Hwang & Jeong Yul Kim (2012): Lithographus, an Abundant Arthropod Trackway from the Cretaceous Haenam Tracksite of Korea, Ichnos: An International Journal for Plant and Animal Traces, 19:1-2, 115-120 To link to this article: http://dx.doi.org/10.1080/10420940.2011.625756 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Ichnos, 19:115–120, 2012 Copyright c Taylor & Francis Group, LLC ISSN: 1042-0940 print / 1563-5236 online DOI: 10.1080/10420940.2011.625756 Lithographus, an Abundant Arthropod Trackway from the Cretaceous Haenam Tracksite of Korea Nicholas J. Minter,1 Martin G. Lockley,2 Min Huh,3 Koo-Geun Hwang,3 and Jeong Yul Kim4 1Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada 2Dinosaur Tracks Museum, University of Colorado, Denver, Colorado, USA 3Faculty of Earth Systems and Environmental Sciences and Korea Dinosaur Research Center, Chonnam National University, Gwangju, Korea 4Department of Earth Science Education, Korea National University of Education, Cheongwon, Korea first considered to be those of swimming sauropods (Lee Trackways ascribed to Lithographus hieroglypichus and at- and Huh, 2002; Thulborn, 2004; Lee and Lee, 2006) but tributed to pterygote insects are described from the Cretaceous later reinterpreted as large ornithopod undertracks caused by Uhangri Formation of Korea. The locality is part of the Haenam progression over unusual substrates (Hwang et al., 2008; Song, Tracksite at the Uhangri Dinosaur Museum Complex, which is 2010). The site has also produced the world’s largest pterosaur famous for dinosaur, pterosaur and bird tracks. This represents the first report of the arthropod trackway Lithographus from tracks, assigned to the ichnogenus Haenamichnus (Lockley the Cretaceous of Korea. The trackways are preserved in cherty et al., 1997; Hwang et al., 2002) and trackways (Uhangrichnus mudstones that formed in the margins of an alkaline lake in the chuni and Hwangsanipes choughi) attributed to birds with vicinity of active volcanoes. Numerous trackways are preserved at webbed feet (Yang et al., 1995). a single horizon. This probably reflects a brief period of exposure In addition, the site reveals a single horizon with a high of balanced-fill lake margin sediments, which provided a window of opportunity for the production and preservation of trackways density of arthropod trackways. This material has previously of insects that inhabited the region rather than a sudden influx of only been illustrated briefly and without detailed comment. insects into the area related to volcanism and a productivity bloom. The first reports and illustrations of the material appeared in an unpublished research report (Huh et al., 1998) compiled at Keywords Arthropod, Continental, Ichnology, Insect, Lake margin, the time the site was being excavated prior to construction of Trackway the Uhangri Dinosaur Museum Complex. Subsequently, Hwang et al. (2002, fig. 3) published a photograph of one of these trackways but did not assign it to any ichnotaxon. No other INTRODUCTION description of these trackways exists, and they have not been The tracksite locality at the Uhangri Dinosaur Museum assigned to an appropriate ichnotaxon. Herein, we provide the Downloaded by [Pukyong National University] at 02:37 22 March 2012 Complex in Haenam-gun County (Figs. 1A–C), situated in first detailed description of these trackways and discuss their the Haenam Basin, is one of the most interesting vertebrate paleoecological significance. tracksites in Asia. In 1998 it was designated as Haenam Tracksite Natural Monument No. 394. The track-bearing units, occurring at several levels in the Uhangri Formation, have GEOLOGICAL SETTING been intensively studied and have produced abundant tracks The Haenam tracksite locality occurs within the Uhangri of dinosaurs, pterosaurs and birds. Most dinosaur tracks have Formation, which is the middle unit of the Haenam Group been attributed to the ichnogenus Caririchnium (Hwang, 2001). in the Haenam Basin of Korea. The Uhangri Formation is There has also been heated debate about some unusual footprints underlain by an andesitic tuff with andesite intrusions and flows and is overlain by the Hwangsan Tuff and Jindo Rhyolite (Lee and Lee, 1976; Chun and Chough, 1995; Hwang et al., 2008). Radiometric dating of tuffs above and below the Uhangri Address correspondence to Nicholas J. Minter, Department of Geological Sciences, University of Saskatchewan, 114 Sci- Formation places age constraints of 96 to 81 Ma (mid- ence Place, Saskatoon, Saskatchewan, S7N 5E2, Canada. E-mail: Cenomanian to Early Campanian) on the trace fossil-bearing [email protected] sequence (Moon et al., 1990; Kim et al., 2003). 115 116 N. J. MINTER ET AL. FIG. 1. A: Location of the Haenam tracksite at the Uhangri Dinosaur Museum Complex (black rectangle). B: Map of the study locality at the Uhangri Dinosaur Downloaded by [Pukyong National University] at 02:37 22 March 2012 Museum Complex. C: Linear outcrop of the Lithographus-bearing layer (stippled, at half scale) parallel to interpretative trail boardwalk and viewing platform (in black). Details of west and east outcrops are also shown with locations of approximately 80 conspicuous Lithographus trackways and those from which replicas (R) were obtained through molding. D: Schematic stratigraphic section of the Upper Cretaceous Uhangri Formation. Lithographus trackways occur at a single horizon and dinosaur, pterosaur, and bird tracks have been found in three layers. A and D redrawn after Hwang et al. (2002). The sedimentology of the Uhangri Formation was described Vertebrate tracks occur at three horizons in the study section. in detail by Chun and Chough (1995). It consists mainly of The most abundant vertebrate tracks occur in the lowermost an epiclastic sequence of conglomerates, sandstones, cherty of these horizons (Figs. 1D, 2A), which consists of laminated mudstones, black shales and volcaniclastics. The upper part black shales with plants and nonmarine ostracods. This is consists of laminated dark gray to black shale, crudely stratified overlain by a unit of convoluted sandstones/cherty mudstones sandstone, convoluted sandstone/cherty mudstone and massive (Figs. 1D, 2; facies S/M2 of Chun and Chough, 1995). This sandstone (Chun and Chough, 1995). Tuffaceous sandstones facies consists of couplets of sandstone and cherty mudstone also occur within the study section at the Uhangri Dinosaur with transitional boundaries between the sandstone and base Museum Complex (Fig. 1D). of the cherty mudstone and sharp upper boundaries (Fig. 2B). CRETACEOUS LITHOGRAPHUS FROM KOREA 117 commonly alkaline or saline and chemically stratified (Bohacs et al., 2000), and the lake waters at the time of deposition of the Haenam arthropod trackway-bearing unit are inferred to have been alkaline and saturated with dissolved silica from the nearby volcanism (Chun and Chough, 1995). The sandstones in the sandstone/cherty mudstone couplets are interpreted to have been deposited by density flows, and such perturbations are suggested to have disrupted the chemical balance of the lake water, which resulted the precipitation of silica in the cherty mudstones (Chun and Chough, 1995). Associated symmetrical ripple marks indicate wave action and that the water was shallow. The single horizon with arthropod trackways suggests that emplacement of the trackways was enabled by temporary exposure of the lake margin sediment. The lack of desiccation features indicates that exposure was probably only brief and is consistent with a balanced-fill lake. SYSTEMATIC ICHNOLOGY The

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