Dinosaur Footprints in Terrigenous Sediments on the Early Jurassic Shelf of the Central North Caucasus: Sedimentological
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saur Footprints in Terrigenous Sediments on the Early Jurassic Shelf of the Central North Caucasus: Sedimentological and Paleoecological Settings Yu. O. Gavrilov* Geological Institute, Russian Academy of Sciences, Moscow, 119017 Russia *e-mail: [email protected] Received April 19, 2020; revised April 19, 2020; accepted April 29, 2020
Abstract—Dinosaur footprints were found in Pliensbachian terrigenous rocks in the central North Caucasus. Tracks of different sizes (12‒35 cm) were identified at three levels of the Mizur Formation section. The sediments accumulated on the wide (15‒20 km) shelf of a paleobasin. The coastal land was covered with abundant vegetation. The warm and humid climate favored the development of weathering crusts, lake–bog systems, and peat accumulation. The seawater temperature ranged from 21 to 25°C. The accumulation of sediments on the shallow shelf and their distribution over the area were influenced by wave activity, currents, and tidal phenomena. At low tide, small dinosaurs visited the shelf zone in order to search for food in the form of benthic fauna, which was abundant in clayey–silty sediments. The simultaneous presence of significantly different–size animal tracks may indicate that large individuals preyed on smaller ones. The presence of dinosaur tracks at different levels of the upper Pliensbachian strata indicates that representatives of the terrestrial fauna periodically visited the paleoshelf during the Domerian. Keywords: North Caucasus, dinosaur footprints, Pliensbachian paleobasin, terrigenous sediments, shallow shelf, low tides DOI: 10.1134/S002449022005003X
INTRODUCTION Dinosaur footprints were identified in one of the upper Pliensbachian sections during lithological study of the Lower and Middle Jurassic sequences of North Ossetia, North Caucasus (Gavrilov, 2005). We found two more footprint levels in the section during the subsequent studies. Since Early Jurassic dinosaur footprints were unknown previously in the Caucasus, this paper is devoted to; (1) description of the detected footprints; (2) analysis of the sedimentological and paleoecological conditions that existed during the deposition of Liassic sediments in this area and was favorable for the occupation by land vertebrates. Extensive literature is devoted to the problem of identifying traces of animal life, including various vertebrates, in the Mesozoic. Dinosaur footprints in sedimentary sequences worldwide are described in numerous publications (Alexander, 1989; Avanzini, 1998; Carvalho, 2004; Currie and Sargeant, 1979; Dinosaur …, 1989; Farlow, 1987; Kuban, 2006; Leonardi, 1987, 1994; Lockley, 1991; Lucas et al., 2006; Milàn and Bromley, 2006; Olsen and Galton, 1984; Olsen et al., 1998; Rubilar-Rogers et al., 2008; The Study …, 1975; Thulborn, 1990; Tverdokhlebov et al., 2002; and others). A comprehensive review of dinosaurian assemblages in northern Eurasia along with
their ecology and paleobiogeography of their habitat is given in (Nesov, 1995 and others). It seems strange that, unlike in the Central Asia
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