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Unusual echinoid resting trace records change in the position of the redox boundary (Palaeogene of the Lesser Caucasus in Georgia)

Uchman Alfred, Lebanidze Zurab, Kobakhidze Nino, Beridze Tamar, Makadze Davit, Lobzhanidze Koba, Khutsishvili Sophio, Chagelishvili Rusudan, Koiava Kakha, Khundadze Nino

Acta Geologica Polonica

2022

Vol. 72, no. 3

317--330

The first recognition of a tracemaker responding to a temporary shift in the redox boundary is recognized. This is recorded by a new trace fossil, Sursumichnus orbicularis igen. et isp. nov., which is established for mound-like structures on the upper surfaces of sandstone beds from the Borjomi Flysch (upper Paleocene–lower Eocene) in the Lesser Caucasus (Georgia). It is connected with the spatangoid echinoid burrow Scolicia de Quatrefages, 1849 and interpreted as a resting trace of the same tracemaker produced after moving up from a deeper position within the sediment. The resting is caused by an episode of unfavourable conditions related to shallowing of the redox boundary. The trace fossil is a component of the Nereites ichnofacies.

Late Cretaceous (Turonian - Coniacian) irregular echinoids of western Kazakhstan (Mangyshlak) and southern Poland (Opole)

Olszewska-Nejbert D.

Acta Geologica Polonica

2007

Vol. 57, no. 1

1-87

During the Late Cretaceous, both Mangyshlak and the Opole area were part of the North European Province, and irregular echinoid faunas during the Turonian and Coniacian in both areas were dominated by holasteroids and spatangoids, in particular by Plesiocorys, Echinocorys and Micraster. Almost 1,000 specimens from both areas have been studied. Taxonomically more varied are the faunas species in 3 genera. One species, Micraster (Micraster) praerogalae, a transitional form between Micraster (Micraster) cortestudinarium(GOLDFUSS) and Micraster (Micraster) rogalae NOWAK, is described as new. Micraster (Micraster) rogalae is markedly diachronous within the North European Province, first appearing in the late Coniacian in Mangyshlak and reaching central and western Europe during the late Early Santonian. A similar pattern is revealed by a large morphotype of Echinocorys ex gr. scutata LESKE. Palaeoecological and actualistic data show the taxa studied to have been shallow infaunal (Catopygus), shallow epifaunal [Conulus (Conulus) subrotundus], deeper infaunal [Micraster (Micraster)], deeper semi-infaunal [Micraster (Gibbaster), Plesiocorys (Sternotaxis) plana], deeper epifaunal [Echinocorys, Plesiocorys (Plesiocorys) placenta], and deeper infaunal (Hemiaster). Echinoid bioevents described originally from the Salzgitter-Salder section (Lower Saxony, Germany) can also be recognised in the Opole area, but not further afield in Mangyshlak.