Paracme
Paracme, as used in biostratigraphy, is a term that describes the interval of temporary disappearance or absence of a taxon. It defines the interval between when a taxon temporarily disappears and when it reappears in biostratigraphical observation.[1] Paracme Base "PB" (lowest occurrence) is used to denote the start of the disappearance, and Paracme Top "PT" (highest occurrence) denotes the reappearance of the taxon.
Notable examples
[edit]There are several instances where paracme have been reported in nannoplankton and sometimes used as a biostratigraphy marker.
- Reticulofenestra pseudoumbiliucus Paracme: a short time interval in the early Miocene during which R. pseudoumbilicus is absent or extremely rare compared with the underlying and overlying segments. The timing of the event is estimated to be between 8.8 Ma and 7.2 Ma in tropical areas.[2][3][4] Studies have also shown that the timing of this interval varies significantly across latitudes, with much shorter durations reported in the mid-latitude regions[2]
- Discoaster pentaradiatus Paracme: Interval of temporary absence of Discoaster pentaradiatus between ~3.90 Ma and 3..6 Ma.
- Discoaster tamalis Paracme
- Sphenolithus heteromorphus Paracme
References
[edit]- ^ Di Stefano, Agata; D’Andrea, Natale Maria; Distefano, Salvatore; Urso, Salvatore; Borzì, Laura; Baldassini, Niccolò; Barbagallo, Viviana (February 2023). "Calcareous Nannofossil Biostratigraphy and Biochronology at ODP Site 1123 (Offshore New Zealand): A Reference Section for the Last 20 Myr in the Southern Ocean". Journal of Marine Science and Engineering. 11 (2): 408. doi:10.3390/jmse11020408. ISSN 2077-1312.
- ^ a b Asanbe, Joseph (2022). The Biogeographical Extent and Global Synchronicity of the Late Miocene Reticulofenestra pseudoumbilicus Paracme. Uppsala universitet, Institutionen för geovetenskaper. OCLC 1372265146.
- ^ NOTARO, AMALIA; RAFFI, ISABELLA; REGHELLIN, DANIELE (2023-02-09). "THE DISTRIBUTION RANGE OF CALCAREOUS NANNOFOSSIL SPECIES <em>RETICULOFENESTRA PSEUDOUMBILICUS</em> IN THE MIOCENE: AN EXAMPLE OF ECOLOGICAL INFLUENCE ON EVOLUTIONARY DEVELOPMENT". Rivista Italiana di Paleontologia e Stratigrafia. 129 (1). doi:10.54103/2039-4942/17769. ISSN 2039-4942. S2CID 256797128.
- ^ Backman, Jan; Raffi, Isabella; Rio, Domenico; Fornaciari, Eliana; Pälike, Heiko (2012-11-01). "Biozonation and biochronology of Miocene through Pleistocene calcareous nannofossils from low and middle latitudes". Newsletters on Stratigraphy. 45 (3): 221–244. doi:10.1127/0078-0421/2012/0022. ISSN 0078-0421.