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Abstract

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.
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Authors and Affiliations

Alfred Uchman
1
Zurab Lebanidze
2
Nino Kobakhidze
3
Tamar Beridze
3
Davit Makadze
4
Koba Lobzhanidze
3
Sophio Khutsishvili
3
Rusudan Chagelishvili
5
Kakha Koiava
2
Nino Khundadze
4

  1. Faculty of Geography and Geology, Institute of Geological Sciences, Jagiellonian University, Gronostajowa3a, 30-387 Kraków, Poland
  2. Department of Geology, Faculty of Exact and Natural Sciences, Iv. Javakhishvili Tbilisi State University, University str. 13, 0186 Tbilisi, Georgia
  3. Alexander Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Politkovskaia 31, 0186 Tbilisi, Georgia
  4. Alexander Tvalchrelidze Caucasian Institute of Mineral Resources, Tbilisi State University, 12 Mindeli str., 0186 Tbilisi, Georgia
  5. Department of Geology and Paleontology, Georgian National Museum, 3 Purtseladze str., 0105 Tbilisi, Georgia
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Abstract

New echinoid material from the Oligocene Chlamys Ledge Member (uppermost part of the Polonez Cove Formation) on King George Island, West Antarctica, includes the “regular” echinoid Caenopedina aleksandrabitnerae sp. n. and poorly preserved spatangoids, here tentatively identified as members of the genus Abatus . Caenopedina aleksandrabitnerae sp. n. is characterized by fully tuberculate genital plates, which sets it apart from most other species in the genus, by the uneven periproctal margin which indicates that periproctal plates were incorporated into the apical disc, and by moderately wide interambulacral plates with a height/width ratio of 1:3. Among the modern Caenopedina species it is closest to the Australian and New Zealand representatives, which is in contrast to previous reviews of Cenozoic Antarctic echinoid faunas that suggested limited relationship to the Australasian region. This is the first record of Caenopedina from Antarctica; it considerably extends its historical distribution to the south.
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Authors and Affiliations

Andreas Kroh

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