N 22 foraminiferous zone

The N 22 foraminiferous zone , often just N 22 , is the youngest foraminiferous zone in the history of the earth. This biozone originated in the equatorial Atlantic and enables an age allocation of subtropical and tropical marine sediments of the Pleistocene and Holocene .

history

The N-zone structure (N is the abbreviation for Neogen) was introduced by WH Blow in 1969 and revised in 1979. He subdivided the 23 million years long Neogene into 22 foraminiferous zones , N 1 to N 22. This original structure was then revised and slightly modified by Stainforth in 1975 and by Srinivasan and Kennet in 1981. In 1985 Berggren changed the N notation of the neogene to M (for Miocene), PL (for Pliocene) and PT for Pleistocene. In 2005 they proceeded in the same way for the Paleogene and created the notation O (for Oligocene), E (for Eocene) and P (for Paleocene).

Biostratigraphic definition

The N 22 foraminiferous zone (in yellow) compared to the different zone schemes

The start of the N recently 22 Foraminiferenzone, as Globigerinoides ruber zone or abbreviated as Pt 1 zone designated ( Engl. Globigerinoides ruber Partial-range zone ), will be the last occurrence (engl. Load appearance date - LAD - or highest occurrence - HO) of the planktonic foraminifere Globigerinoides fistulosus . This type of foraminifera disappeared 1.88 million years ago BP at the end of N 21 at the exit of the Gelasium ( Upper Pliocene ) or immediately after the end of the magnetic Chron C 2r .

Due to the last appearance of Globorotalia tosaensis 0.61 million years ago BP, N 22 can be divided into two subzones:

• Globorotalia truncatolinoides-Subzone - Pt 1b-Subzone (Partial-range Subzone)
• Globorotalia tosaensis subzone - Pt 1a subzone (highest-occurrence subzone). It was still referred to as Globigerinoides fistulosus-Globorotalia tosaensis Interval Sub-Zone by Berggren in 1995 (a) .

Since N 22 extends to the present (Holocene), it also contains all recently occurring Foraminiferentaxa such. B. Globigerinoides sacculifer , which makes up 80% of tropical plankton .

Examples of taxa found in N 22 are:

• Genus Bolliella :
  • Bolliella calida ( first appearance date - FAD or lowest occurrence - LO - 0.22 million years BP). Formerly Globigerinella calida .
• Genus Globigerina :
  • Globigerina cariacoensis , Globigerina juvenilis .
• Genus Globigerinita :
  • Globigerinita glutinata .
• Genus Globigerinoides :
  • Globigerinoides ruber (LAD of the pink variety Globigerinoides ruber rosa 0.12 million years ago BP), Globigerinoides sacculifer , Globigerinoides trilobus .
• Genus Globoquadrina :
  • Globoquadrina pseudofoliata .
• Genus Globorotalia :
  • Globorotalia crassaformis hessi (FAD 0.75 million years ago BP), Globorotalia crassaformis viola , Globorotalia excelsa (FAD 1.0 million years ago BP), Globorotalia fimbriata , Globorotalia flexuosa (LAD 0.07 million years ago BP), Globorotalia hirsuta ( FAD 0.45 million years ago BP), Globorotalia menardii , Globorotalia tosaensis (LAD 0.61 million years ago BP), Globorotalia truncatolinoides , Globorotalia tumida flexuosa , Globorotalia ungulata .
• Genus Globoturborotalita :
  • Globoturborotalita apertura (LAD 1.63 million years ago BP), Globoturborotalita obliquus (LAD 1.3 million years ago BP).
• Genus Neogloboquadrina :
  • Neogloboquadrina acostaensis , Neogloboquadrina dutertrei .
• Genus Orbulina :
  • Orbulina universa .
• Genus Pulleniatina :
  • Pulleniatina finalis , Pulleniatina obliquiloculata .
• Genus Sphaeroidinella :
  • Sphaeroidinella dehiscens .

Stratigraphic equivalents

The foraminiferous zone N 22 is at the same time as the magnetic Chron C 1 and C 2n (C 2n, however, began already 1.95 million years ago BP).

Biostratigraphic equivalents are the nannoplankton zones (calcareous coccoliths ) NN 19 , NN 20 and NN 21 (or CN 13, CN 14 and CN 15), the dinoflagellate zones D 21 b and D 21 c , the radiolarian zones RN 12 b , RN 13 , RN 14 , RN 15 , RN 16 and RN 17 and the diatom zones NPD 10 , NPD 11 and NPD 12 .

N 22 is roughly congruent with the foraminiferous zone PT 1 of Berggren established in 1995 in the western Atlantic. In the Mediterranean region , N 22 is represented by the foraminifera zones MPL 6 (upper half), MPL 7 and MPL 8. In the Pacific area , the zones Pl 5/6 (uppermost section), Pt 1a and Pt 1b are to be used.

literature

• F, Gradstein et al: A Geological Time Scale 2004 . Cambridge University Press, 2004, ISBN 0-521-78673-8 .
• BS Wade et al .: Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the Geomagnetic Polarity and Astronomical Time Scale . 2011.

Individual evidence

1. ^ WH Blow: Late middle Eocene to Recent planktonic foraminiferal biostratigraphy . In: P. Bronniman, HH Renz (Ed.): Proceedings of the First International Conference on Planktonic Microfossils 1967 . tape 1 , 1969, p. 199-242 .
2. ↑ MS Srinivasan, JP Kennet: Neogene planktonic foraminiferal biostratigraphy and evolution: equatorial to subantarctic, South Pacific . In: Marine Micropaleontology . tape 6 , 1981, pp. 499-533 .
3. ↑ ^{a b} W. A. ​​Berggren, DV Kent, CC Swisher III, M.-P. Aubry: A revised Cenozoic geochronology and chronostratigraphy . In: WA Berggren, DV Kent, M.-P. Aubry, J. Hardenbol (Ed.): Geochronology, Time Scales and Global Stratigraphic Correlation: A Unified Temporal Framework for an Historical Geology, SEPM Spec. Publ. Volume 54 , 1995, pp. 129-212 .
4. ^ WA Berggren, PN Pearson: A revised tropical and subtropical Paleogene planktonic foraminiferal zonation . In: Journal of Foraminiferal Research . tape 35 , 2005, pp. 279-298 .
5. ↑ ^{a b} B. S. Wade et al .: Review and revision of Cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the Geomagnetic Polarity and Astronomical Time Scale . 2011.
6. ↑ FL Parker: Living planktonic foriminifera from the Equatorial and Southeast Pacific . In: Science Report Tohoku University . 2nd series (Geol.) 4. Sendai, Japan 1960, pp. 71-82 .
7. ^ PR Thompson, AWH Bé, J.-C. Duplessy, NJ Shackleton: Disappearance of pink-pigmented Globigerinoides ruber at 120,000 yr BP in the Indian and Pacific oceans . In: Nature . tape 280 , 1979, pp. 554-558 .
8. ↑ GCH Chaproniere, MJ Styzen, WW Sager, H. Nishi, PJ Quinterno, N. Abrahamsen: Late Neogene biostratigraphic and magnetostratigraphic synthesis . In: Proceeding of the Ocean Drilling Program, Scientific Results . tape 135 , 1994.
9. ↑ ^{a b} W. A. ​​Berggren, FJ Hilgen, CG Langereis, DV Kent, JD Obradovich, I. Raffi, ME Raymo, NJ Shackleton ,: Late Neogene chronology: new perspectives in high-resolution stratigraphy . In: Geological Society of America Bulletin . tape 107 , 1995, pp. 1272-1287 (a).
10. ↑ C. Pujol, J. Duprat: Quaternary planktonic foraminifers of the southwestern Atlantic ( Rio Grande Rise ) Deep Sea Drilling Project Leg 72 . In: PF Barker, RL Carlson, DA Johnson et al. (Eds.): Initial Reports of the Deep Sea Drilling Project 72 . Washington (US Govt. Printing Office) 1983, p. 601-615 .
11. ^ AC Mix, J. Le, NJ Shackleton: Benthic foraminiferal stable isotope stratigraphy of Site 846: 0-1.8 Ma . In: NG Pisias, LA Mayer, TR Janecek, A. Palmer-Julson, TH van Andel (Eds.): Proceeding of the Ocean Drilling Program, Scientific Results . tape 138 , 1995, pp. 839-854 .
12. ↑ ^{a b} Chaisson, W. P and Pearson, P. N: Planktonic foraminifer biostratigraphy at Site 925: Middle Miocene - Pleistocene . In: NJ Shackleton, WB Curry, C. Richter, TJ Bralower (Eds.): Proceeding of the Ocean Drilling Program, Scientific Results . tape 154 , 1997, pp. 3-31 .