Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific
Variability in the test of Globorotalia menardii during the past 8 million years has been investigated at DSDP Site 502A (Caribbean Sea) and DSDP Site 503A (Eastern Equatorial Pacific). Measurements were made of spire height (∂x), maximum diameter (∂y), the tangent angles of the upper and lower peri...
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Association Carnets de Geologie
2007
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ftdoajarticles:oai:doaj.org/article:6dc52d92845d423f86e86dc421b591ff 2023-10-01T03:59:02+02:00 Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific Knappertsbusch Michael 2007-07-01T00:00:00Z https://doaj.org/article/6dc52d92845d423f86e86dc421b591ff EN FR eng fre Association Carnets de Geologie http://paleopolis.rediris.es/cg/CG2007_A04/index.html https://doaj.org/toc/1765-2553 https://doaj.org/toc/1634-0744 1765-2553 1634-0744 https://doaj.org/article/6dc52d92845d423f86e86dc421b591ff Carnets de Géologie, Vol CG2007, p A04 (2007) Globorotalia menardii Neogene evolution Isthmus of Panama morphometrics Geology QE1-996.5 Paleontology QE701-760 Stratigraphy QE640-699 article 2007 ftdoajarticles 2023-09-03T00:42:08Z Variability in the test of Globorotalia menardii during the past 8 million years has been investigated at DSDP Site 502A (Caribbean Sea) and DSDP Site 503A (Eastern Equatorial Pacific). Measurements were made of spire height (∂x), maximum diameter (∂y), the tangent angles of the upper and lower peripheral keels (Φ1, Φ2, respectively), the number of chambers in the final whorl, and the area of the silhouette in keel view. Four morphotypes alpha, beta, gamma, and delta were distinguished. Morphotype alpha was found in strata ranging in age from the Late Miocene through the Holocene. It shows a continuous increase in ∂x and ∂y until the Late Pleistocene. During and after the final closure of the ancient Central American Seaway (between 2.4 Ma and 1.8 Ma) there was a rapid increase in the area of the test in keel view. At the Caribbean Sea site, morphotype beta evolved during the past 0.22 Ma. It is less inflated than alpha and has a more delicate test. In the morphospace of ∂x vs. ∂y, morphotypes alpha and beta can be distinguished by a separation line ∂y = 3.2 * ∂x - 160 (∂x and ∂y in µm). Plots of morphotype alpha are below that line, those of beta are above it. Morphotype alpha is taken to be Globorotalia menardii menardii Parker, Jones & Brady (1865) and includes G. menardii 'A' Bolli (1970). Morphotype beta is identified as G. menardii cultrata (d'Orbigny). Morphotypes gamma and delta are extinct Upper Miocene to Pliocene forms which evolved from morphotype alpha. They have a narrower Φ1 angle and more chambers (≥7) than morphotype alpha commonly with 5 to 6 chambers (7 in transitional forms). In contemporaneous samples morphotype delta can be distinguished from gamma by a smaller value of Φ1 and 8 or more chambers in the final whorl. Morphotype gamma is taken to be G. limbata (Fornasini, 1902) and includes the junior synonym G. menardii 'B' Bolli (1970). Morphotype delta is G. multicamerata Cushman & Jarvis (1930). With the exception of the Late Pleistocene development of G. menardii cultrataonly in ... Article in Journal/Newspaper Planktonic foraminifera Directory of Open Access Journals: DOAJ Articles Pacific |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English French |
topic |
Globorotalia menardii Neogene evolution Isthmus of Panama morphometrics Geology QE1-996.5 Paleontology QE701-760 Stratigraphy QE640-699 |
spellingShingle |
Globorotalia menardii Neogene evolution Isthmus of Panama morphometrics Geology QE1-996.5 Paleontology QE701-760 Stratigraphy QE640-699 Knappertsbusch Michael Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific |
topic_facet |
Globorotalia menardii Neogene evolution Isthmus of Panama morphometrics Geology QE1-996.5 Paleontology QE701-760 Stratigraphy QE640-699 |
description |
Variability in the test of Globorotalia menardii during the past 8 million years has been investigated at DSDP Site 502A (Caribbean Sea) and DSDP Site 503A (Eastern Equatorial Pacific). Measurements were made of spire height (∂x), maximum diameter (∂y), the tangent angles of the upper and lower peripheral keels (Φ1, Φ2, respectively), the number of chambers in the final whorl, and the area of the silhouette in keel view. Four morphotypes alpha, beta, gamma, and delta were distinguished. Morphotype alpha was found in strata ranging in age from the Late Miocene through the Holocene. It shows a continuous increase in ∂x and ∂y until the Late Pleistocene. During and after the final closure of the ancient Central American Seaway (between 2.4 Ma and 1.8 Ma) there was a rapid increase in the area of the test in keel view. At the Caribbean Sea site, morphotype beta evolved during the past 0.22 Ma. It is less inflated than alpha and has a more delicate test. In the morphospace of ∂x vs. ∂y, morphotypes alpha and beta can be distinguished by a separation line ∂y = 3.2 * ∂x - 160 (∂x and ∂y in µm). Plots of morphotype alpha are below that line, those of beta are above it. Morphotype alpha is taken to be Globorotalia menardii menardii Parker, Jones & Brady (1865) and includes G. menardii 'A' Bolli (1970). Morphotype beta is identified as G. menardii cultrata (d'Orbigny). Morphotypes gamma and delta are extinct Upper Miocene to Pliocene forms which evolved from morphotype alpha. They have a narrower Φ1 angle and more chambers (≥7) than morphotype alpha commonly with 5 to 6 chambers (7 in transitional forms). In contemporaneous samples morphotype delta can be distinguished from gamma by a smaller value of Φ1 and 8 or more chambers in the final whorl. Morphotype gamma is taken to be G. limbata (Fornasini, 1902) and includes the junior synonym G. menardii 'B' Bolli (1970). Morphotype delta is G. multicamerata Cushman & Jarvis (1930). With the exception of the Late Pleistocene development of G. menardii cultrataonly in ... |
format |
Article in Journal/Newspaper |
author |
Knappertsbusch Michael |
author_facet |
Knappertsbusch Michael |
author_sort |
Knappertsbusch Michael |
title |
Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific |
title_short |
Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific |
title_full |
Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific |
title_fullStr |
Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific |
title_full_unstemmed |
Morphological variability of Globorotalia menardii(planktonic foraminifera) in two DSDP cores from the Caribbean Sea and the Eastern Equatorial Pacific |
title_sort |
morphological variability of globorotalia menardii(planktonic foraminifera) in two dsdp cores from the caribbean sea and the eastern equatorial pacific |
publisher |
Association Carnets de Geologie |
publishDate |
2007 |
url |
https://doaj.org/article/6dc52d92845d423f86e86dc421b591ff |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
Planktonic foraminifera |
genre_facet |
Planktonic foraminifera |
op_source |
Carnets de Géologie, Vol CG2007, p A04 (2007) |
op_relation |
http://paleopolis.rediris.es/cg/CG2007_A04/index.html https://doaj.org/toc/1765-2553 https://doaj.org/toc/1634-0744 1765-2553 1634-0744 https://doaj.org/article/6dc52d92845d423f86e86dc421b591ff |
_version_ |
1778532461657980928 |