New Findings of Lower Cambrian Trilobites in the Southern Hövsgöl Area (Mongolia) and Their Significance for Stratigraphy and Interregional Correlation

Abstract

—Based on the materials collected by L.N. Repina in the southern Hövsgöl area (Mongolia) in 1986–1988, we describe three sections and identify lower Cambrian trilobites. The sections of Mt. Hurtel Harna and along the Ujigin Gol River were studied earlier. We consider trilobites that have been found in these sections for the first time: Redlihia zharkovi, Lermontoviella shanganica, Erbia granulosa, Kootenia siberica, and Parapoulsenia lata. The section along the ravine of the Zuun-Shuvuutyn-Sair Brook and the findings of trilobites in it are described for the first time. The found new trilobites make it possible to correlate the coeval lower Cambrian strata in the southern Hövsgöl area, Altai–Sayan folded area, and western Siberian Platform and refine the age of the certain parts of the Egyin Gol, Ukhaa Tolgoi, and Ujigin Gol formations.

New trilobite assemblage from the lower Cambrian (upper Stage 4) of the Lake Zone, western Mongolia

“…These faunal beds yielded trilobites of the genera Alokistocare , Chilometopus , Chondragraulos , Edelsteinaspis , Erkelina , Kootenia , Kootenina (= Olenoides ), Kooteniella , Laminurus , Pegetides , Piriforma (= Dinesus ), and Solontzella . An approximately coeval trilobite assemblage from the Khuvsgul terrane (Udzhigin-Gol Formation) also was described (Korobov, 1989; Korovnikov and Lazarev, 2021). In this area, trilobites are mostly represented by the genera Redlichia , Inouyina , Edelsteinaspis , Dinesus , Kootenia , Lermontoviella , Parapoulsenia , Chondragraulos , and Onchocephalina .…”

“…In contrast, our knowledge of facies and fossils from other former tectonic zones is still almost in its infancy. A few archaeocyaths and small shelly fossils from the Lake, Khan-Khukhiy, and Khuvsgul regions have been described (Vologdin, 1940; Zhuravleva, 1972; Voronin, 1988; Esakova and Zhegallo, 1996; Demidenko et al, 2003; Malakhovskaya, 2014), and some trilobite faunas were described from the Lake, Ider, and Khuvsgul regions (Dumicz et al, 1970; Blagonravov et al, 1971; Korobov, 1980, 1989; Korovnikov and Lazarev, 2021). The youngest of these assemblages is represented almost exclusively by paradoxidid trilobites of the Khovd Aimak (region), the Mongolian Altay and assigned to the former middle Cambrian Amgan Stage of Siberia (Dumicz et al, 1970).…”