Disruption of playa–lacustrine depositional systems at the Permo-Triassic boundary: evidence from Vyazniki and Gorokhovets on the Russian Platform

Abstract

The geological section in the Zhukov ravine is represented by two packets of rocks: a lower mudstone-siltstone packet and an upper sandstone packetThe lower mudstone-siltstone packet is represented in exposures 1 and 2. Ostracods from the bottom packet are selected from marls and limestones lying 2 -3 m below the top.

Cretaceous stem chondrichthyans survived the end-Permian mass extinction

“…Before this discovery, the last known unambiguous representatives of the superorder Cladodontomorphii (Symmoriiformes and Ctenacanthiformes, see refs 4,10) were Late Permian in age 4,[11][12][13] . All allegedly Triassic cladodontomoph shark occurrences have been re-evaluated (for example, the Middle Triassic Acronemus tuberculatus 14 ) or have very dubious taxonomic values (Early Triassic fin spines 15 and denticles 16 ).…”

The westernmost occurrence of <i>Gnathorhiza</i> in the Triassic, with a discussion of the stratigraphic and palaeogeographic distribution of the genus

“…It is recorded from the European part of Russia and from Kazakhstan ( Fig. 2b; Minikh, 1977Minikh, , 1995Newell et al, 2010). Its fossils were found in Induan and lower Olenekian sediments gathered in "the first ichthyofaunal complex" (sensu Minikh, 1995) and Vetlugian Gorizont (sensu Minikh, 1997, 2006).…”

“…In the upper Olenekian sediments ("II ichthyofaunal complex", Yarenskian Gorizont) of south pre-Uralian and northern Caspian region Gnathorhiza findings are accompanied with Arganodus, Ceratodus and Ptychoceratodus fossils (Minikh, 1977(Minikh, , 1995Minikh, 1997, 2006). All Lower Triassic sediments of Russia and Kazakhstan yielding gnathorhizid remains are of lacustrine-alluvial origin (Minikh, 1995;Newell et al, 2010).…”

“…: Brazil, Rio Grande do Sul State, Rio do Rasto Formation (Ragonha, 1989;Richter and Langer, 1998); 14, Gnathorhiza sp. : Oman, Al Wusta region, Gharif Formation (Schultze et al, 2008); 15, Gnathorhiza otschevi: Poland, Czatkowice 1, karst fillings (this paper); 16, G. triassica triassica, G. triassica baskunchakensis, G. triassica beresnikiensis: Russia, Arkhangelsk Oblast (Minikh, 1977); 17, G. triassica triassica: Russia, Komi Republic (Minikh, 1977);18, G. triassica triassica, G. triassica baskunchakensis: Russia, Kirov Oblast (Minikh, 1977);19, G. triassica triassica, G. triassica beresnikiensis, G. lozovskii, G. bogdensis: Russia, Vologda Oblast (Minikh, 1977);20, G. otschevi, G. triassica triassica, G. triassica beresnikiensis, G. bogdensis: Russia, Kostroma Oblast (Minikh, 1977);21, G. triassica triassica, G. lozovskii: Russia, Yaroslavl Oblast (Minikh, 1977;Novikov and Sennikov, 1997); 22, Gnathorhiza otschevi: Russia, Vladimir Oblast (Newell et al, 2010); 23, G. triassica triassica: Russia, Nizhny Novgorod Oblast (Minikh, 1977(Minikh, , 2000; 24, G. otschevi, G. triassica triassica, G. triassica beresnikiensis, G. triassica baskunchakensis, G. lozovskii: Russia, Orenburg Oblast (Minikh, 1977;Minikh and Minikh, 1997); 25, G. triassica triassica, G. triassica baskunchakensis: Kazakhstan, Atyrau Oblast (Minikh and Minikh, 1997); 26, G. otschevi, G. triassica baskunchakensis, G. bogdensis: Russia, Bolshoye Bogdo Mountain (Minikh, 1977;Minikh and Minikh, 1997). Numbers not in stratigraphic order.…”

“…In the Late Permian, Gnathorhiza occurred in Russia (Minikh, 1989;Minikh and Minikh, 2006) and Brazil (Toledo and Bertini, 2005). The youngest fossils of Gnathorhiza are known from the Lower Triassic freshwater sediments of Russia (Minikh, 1977(Minikh, , 2000Minikh and Minikh, 2006;Newell et al, 2010) and Poland (Borsuk-Białynicka et al, 2003).…”