Canadian Journal of Earth Sciences LITHOBIOTOPES OF THE NEMEGT GOBI BASIN Journal: Canadian Journal of Earth Sciences Manuscript ID cjes-2020-0148.R1 Manuscript Type: Article Date Submitted by the 17-Nov-2020 Author: Complete List of Authors: Jerzykiewicz, Tomasz; retired Currie, Philip J.; University of Alberta, Biological Sciences Fanti, Federico; Departmen of Earth and Geoenvironmental Sciences, University of Bologna Lefeld, Jerzy; retired Keyword: Mongolia, UpperDraft Cretaceous, Lithobiotope, Dinosaurs Is the invited manuscript for consideration in a Special Tribute to Dale Russell Issue? : © The Author(s) or their Institution(s) Page 1 of 81 Canadian Journal of Earth Sciences 1 LITHOBIOTOPES OF THE NEMEGT GOBI BASIN 2 3 Tomasz Jerzykiewicz, Philip J. Currie, Federico Fanti and Jerzy Lefeld 4 5 T. Jerzykiewicz. Research scientist and exploration geologist, Montréal, PQ, Canada. 6 P.J. Currie. Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 7 2E9, Canada. 8 F. Fanti. Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum, 9 Università di Bologna, Via Zamboni 67, 40126 Bologna, Italy. 10 J. Lefeld. Research scientist, Polish Academy of Sciences, Warszawa, Poland. 11 [email protected]. Draft 12 13 Corresponding authors. T. Jerzykiewicz (email: [email protected]) and P.J. Currie 14 (email: [email protected]). 15 16 17 18 19 20 21 22 23 © The Author(s) or their Institution(s) Canadian Journal of Earth Sciences Page 2 of 81 24 Abstract: Three distinct but overlapping dinosaur-dominated faunas characterize the Upper 25 Cretaceous Djadokhta, Baruungoyot and Nemegt formations of the Nemegt Basin of Mongolia. 26 Documented faunal differences cannot be explained easily by temporal succession, but can be 27 understood in the light of physical processes controlling life, death, and burial of taxa. The 28 stratigraphy of the Gobi Desert region records tectonically driven geometries, clearly 29 documenting preservational processes different than those acting in most other dinosaur- 30 dominated beds worldwide. Small, asymmetric tectonic grabens were filled with Upper 31 Cretaceous, dinosaur bearing deposits showing asymmetric distributions of facies, here termed 32 Lithobiotopes. The water-lain fluvial and alluvial plain facies of the Nemegt Lithobiotope 33 supported and preserved a fauna dominated by gigantic dinosaurs, but had a preservational bias 34 against smaller animals. The Nemegt passedDraft laterally into interdune facies of the Baruungoyot 35 Lithobiotope, which represented a hostile environment for large species, but preserved smaller 36 animals. This in turn passed laterally into the aeolianite facies of the Djadokhta Lithobiotope, 37 which is characterized by remains of small dinosaurs and a rich fauna of other animals. The 38 Nemegt Gobi Basin can be visualized as an oasis with a central pond supplied with water from 39 ephemeral channels and surrounded by a semi-arid alluvial plain and dune fields. 40 41 Key words: Mongolia, Upper Cretaceous, Lithobiotope, dinosaurs 42 43 Résumé: To be translated by the journal. 44 Mots-clés: Mongolie, Crétacé supérieur, Lithobiotope, dinosaure 45 46 © The Author(s) or their Institution(s) Page 3 of 81 Canadian Journal of Earth Sciences 47 48 49 50 51 52 53 Introduction 54 The Late Cretaceous dinosaurs from the Gobi Desert have been the subject of enormous 55 interest since their discovery by American expeditions one hundred years ago (Andrews 1923, 56 1932; Berkey 1924a, 1924b). Unearthed rather unexpectedly in a desert, the dinosaurs from 57 southern Mongolian localities became anDraft instant sensation and the subject of original 58 palaeontological publications (Granger and Gregory 1923; Osborn 1924a, b; Gilmore 1933) and 59 popular books (Andrews 1921, 1926, 1953; Gallenkamp 2001; Jerzykiewicz 2018). The interest 60 of palaeontologists in exploration of the Gobi localities has not diminished. On the contrary, 61 palaeontologists from all over the world continue to be attracted to the region (for an extensive 62 and up-to-date review see Fanti et al. 2018). Of special interest are the world-renowned localities 63 in the Nemegt Basin where a rich and diverse dinosaur-dominated fauna and continuous 64 exposures have continued to attract multinational expeditions (Kielan-Jaworowska 1968; Lavas 65 1993; Novacek 1996; Fanti et al. 2018). The geological signatures of the dinosaur habitats from 66 the Gobi Desert have also been studied and publicized (Berkey and Morris 1927; Gradziński 67 1970; Gradziński and Jerzykiewicz 1974a, b; Jerzykiewicz and Russell 1991; Fastovsky et al. 68 1997; Hicks et al. 1999; Dingus et al. 2008; Eberth et al. 2009; Eberth 2018). Despite such 69 premises, the stratigraphy and sedimentary environments of the Gobi habitats are controversial © The Author(s) or their Institution(s) Canadian Journal of Earth Sciences Page 4 of 81 70 and, as a matter of fact, these controversies remain largely unresolved. The reasons are manifold. 71 Progress in sedimentary geology combined with new field observations have made most of the 72 initial interpretations obsolete. Insufficient and frequently localized observations resulted in 73 speculation rather than a comprehensive stratigraphic analysis of the basin. However, despite 74 many unfruitful attempts, the most outstanding issue is the lack of stratigraphical interpretations 75 on the genesis and correlativity of the Upper Cretaceous strata. 76 The geographic extension, nature and age of the boundaries dividing each of the major 77 fossil units (Djadokhta, Baruungoyot and Nemegt formations) remain poorly understood as the 78 lack of continuous exposures limits our possibilities to address these critical questions. 79 Makovicky (2008) found that the Djadokhta sites were probably progressively younger to the 80 west, and found weak support that UkhaaDraft Tolgod may even be contemporaneous with 81 Baruungoyot beds. This is a conclusion also suggested faunally by Kielan-Jaworowska et al. 82 (2003). 83 Furthermore, two irreconcilable classifications have been used to describe stratigraphy of 84 the Cretaceous of Mongolia. The Russian explorers, ignoring stratigraphy previously introduced 85 by the American expeditions of the 1920s, utilized their own stratigraphic classification and still 86 insist on their application (Shuvalov 2000). This fact is causing considerable confusion in the 87 correlation of the Upper Cretaceous dinosaur-bearing strata – starting with nomenclatural issues - 88 and controversies in understanding of the habitats in which the dinosaurs lived (for a 89 comprehensive discussion of the problem see Jerzykiewicz, 2000). Recent attempts to create a 90 single, stratigraphic framework within which detailed and more localized geological 91 observations could be placed provided useful insights into the lithostratigraphy of the area, and 92 also documented how different palaeoenvironments can be traced in the area. Nonetheless, such © The Author(s) or their Institution(s) Page 5 of 81 Canadian Journal of Earth Sciences 93 interpretations are not supported by structural analyses at a basin scale, rely on stratigraphic 94 patterns rather than observable marker beds, lack data from key areas where exposures provide 95 crucial information on the reciprocal architecture of the sedimentary units, and do not improve 96 our understanding on the relationship between fossil spatial and stratigraphic occurrence and 97 depositional settings in the Cretaceous (Hicks et al. 1999; Eberth 2018). 98 The present situation can be described as a scientific crisis, especially in the light of the 99 relevance of the Gobi basin for our comprehension of Late Cretaceous ecosystems. It is the 100 purpose of this paper to offer a solution of this predicament by proposing a new genetic 101 classification of the dinosaur-bearing strata of the area. Instead of using either formation or the 102 Russian svita, we propose to use a unit called a lithobiotope. Lithobiotope integrates the 103 lithology of the sediments that entomb theDraft dinosaur remains with the habitats of the dinosaur 104 assemblage. 105 This paper is based on firsthand experience that all of the authors gained during fieldwork 106 in expeditions to the Gobi Desert. The first author served as the geologist of the 1971 Polish- 107 Mongolian Palaeontological Expedition, was the geologist of the 1988 Sino-Canadian 108 Palaeontological Expedition, and returned to the Ordos Basin of China in 1990 (sponsored by the 109 Canadian Museum of Nature). The second author was co-leader of the Sino-Canadian 110 Palaeontological Expeditions in the Chinese part of the Gobi Desert from 1985 to 1990, and was 111 the Canadian leader of various expeditions to collect dinosaurs in Mongolia every year since 112 1999. The third author was on a Dinosaurs of the Gobi expedition in 2007, and led two National 113 Geographic funded expeditions into the Nemegt Basin in 2016 and 2018. The fourth author is a 114 veteran of the first Polish-Mongolian Palaeontological Expeditions in the years 1964 and 1965. © The Author(s) or their Institution(s) Canadian Journal of Earth Sciences Page 6 of 81 115 The expertise of the authors covers all known dinosaur-bearing localities of southern Mongolia, 116 plus some localities in the Chinese Gobi Desert and the Ordos Basin of China. 117 Mongolian place and stratigraphic names have been spelled in many different ways. To 118 minimize confusion, the standards suggested by Benton et al. (2000) are used in