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First evidence of Palaeo-Tethyan Upper Triassic calcareous nannofossils in North Dobrogean Orogen (Romania)

Demangel, Isaline LU orcid ; Bucharest, University ; Lazăr, Iuliana ; Seghedi, Antoneta and Munteanu, Ioan (2024) In Rivista Italiana di Paleontologia e Stratigrafia 130(1). p.81-96
Abstract
This study presents the analysis of Upper Triassic sediments from five locations in North Dobrogea (Romania) and the Black Sea. Microfacies analyses on thin sections from the Frecăţei log reveal a shallowing trend and likely an increase in energy upward into the section. The oldest part of the log is characterised by deposition of mudstones transitioning to wackestones, with an increase of bivalves. Similar wackestones are observed in the Izvoarele and Rândunica logs, i.e. microfacies with abundant bivalves, some foraminifera and echinoderms. The off-shore boreholes 816 and 817 Lebăda Vest (core CM 9 and CM 31) seem to have been deposited in a basinal or distal marine shelf environment indicated by ... (More)
This study presents the analysis of Upper Triassic sediments from five locations in North Dobrogea (Romania) and the Black Sea. Microfacies analyses on thin sections from the Frecăţei log reveal a shallowing trend and likely an increase in energy upward into the section. The oldest part of the log is characterised by deposition of mudstones transitioning to wackestones, with an increase of bivalves. Similar wackestones are observed in the Izvoarele and Rândunica logs, i.e. microfacies with abundant bivalves, some foraminifera and echinoderms. The off-shore boreholes 816 and 817 Lebăda Vest (core CM 9 and CM 31) seem to have been deposited in a basinal or distal marine shelf environment indicated by the presence of mudstones with rare bioclasts. In contrast, sample CM 10 from borehole 816 LV is a micritised grainstone suggesting a deposition in a shallower, higher energy environment. Scanning electron microscope observations reveal a moderate diagenetic alteration in all studied samples, mainly due to dissolution. Two calcareous nannofossil species: Prinsiosphaera triassica triassica and Eoconusphaera zlambachensis were commonly observed in sample F of the Frecăţei log, allowing for assignment of the sediments to the Rhaetian age. Two coccoliths were also observed in sample F of Frecăţei log and sample CM 9 of the borehole 816 LV indicating the presence of coccolithophorids within the study region. This discovery constitutes the first confirmed record of well-preserved, determinable Upper Triassic calcareous nannofossils in the Palaeo-Tethys Ocean. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Prinsiosphaera triassica, Eoconusphaera zlambachensis, Rhaetian, Frecăţei, Borehole 816 LV, Black Sea, Palaeo-Tethys
in
Rivista Italiana di Paleontologia e Stratigrafia
volume
130
issue
1
pages
16 pages
ISSN
2039-4942
DOI
10.54103/2039-4942/19776
language
English
LU publication?
yes
id
50403386-fde8-4e95-b391-3b5c35adacd9
date added to LUP
2024-03-19 11:15:57
date last changed
2024-03-19 14:35:45
@article{50403386-fde8-4e95-b391-3b5c35adacd9,
  abstract     = {{This study presents the analysis of Upper Triassic sediments from five locations in North Dobrogea (Romania) and the Black Sea. Microfacies analyses on thin sections from the Frecăţei log reveal a shallowing trend and  likely  an  increase in  energy  upward  into  the  section.  The  oldest  part  of   the  log  is characterised  by  deposition  of   mudstones  transitioning  to  wackestones, with  an  increase  of   bivalves.  Similar  wackestones  are  observed  in  the Izvoarele and Rândunica logs, i.e. microfacies with abundant bivalves, some foraminifera and echinoderms. The off-shore boreholes 816 and 817 Lebăda Vest (core CM 9 and CM 31) seem to have been deposited in a basinal or distal marine  shelf   environment  indicated  by  the  presence  of   mudstones  with rare  bioclasts.  In  contrast,  sample  CM  10  from borehole 816 LV is a micritised grainstone suggesting a deposition in a shallower, higher energy environment. Scanning electron microscope observations reveal a moderate diagenetic alteration in all studied samples, mainly due to dissolution. Two calcareous nannofossil species: Prinsiosphaera triassica triassica and Eoconusphaera zlambachensis were commonly observed in sample F of the Frecăţei log, allowing for assignment of the sediments to the Rhaetian age. Two coccoliths were also observed in sample F of Frecăţei log and sample CM 9 of the borehole 816 LV indicating the presence of coccolithophorids within the study region. This discovery constitutes the first confirmed record of well-preserved, determinable Upper Triassic calcareous nannofossils in the Palaeo-Tethys Ocean.}},
  author       = {{Demangel, Isaline and Bucharest, University and Lazăr, Iuliana and Seghedi, Antoneta and Munteanu, Ioan}},
  issn         = {{2039-4942}},
  keywords     = {{Prinsiosphaera triassica; Eoconusphaera zlambachensis; Rhaetian; Frecăţei; Borehole 816 LV; Black Sea; Palaeo-Tethys}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{1}},
  pages        = {{81--96}},
  series       = {{Rivista Italiana di Paleontologia e Stratigrafia}},
  title        = {{First evidence of Palaeo-Tethyan Upper Triassic calcareous nannofossils in North Dobrogean Orogen (Romania)}},
  url          = {{https://lup.lub.lu.se/search/files/177606823/Demangel_et_al_2024.pdf}},
  doi          = {{10.54103/2039-4942/19776}},
  volume       = {{130}},
  year         = {{2024}},
}