Some of the SEM-photographed specimens display characteristics transitional between Pg. However, all the latest hypotheses suggest that Subbotina evolved from Eoglobigerina. El estudio de cortes doraminiferos altas latitudes Keller, ; Keller et al. Foraminuferos contrast, the test of E. The Globigerinoides primordius Zone spanning the lowermost part of the section and assigned to the Aquitanian early Miocene. Over SEM-photographs, including different views and details of the surface of the tests of specimens, were taken.

Author:Akigrel Zunos
Language:English (Spanish)
Published (Last):17 August 2007
PDF File Size:17.73 Mb
ePub File Size:10.37 Mb
Price:Free* [*Free Regsitration Required]

Parasubbotina moskvini was not considered by either Olsson et al. Geographical coordinates of all strati-graphic sections are given in Appendix 1. Most of the Elphidium genus shows strong diversity and dissolution with small-size test. Whereas the next zonal marker, Globigerinoides trilobusis not recorded in this zone and makes its first occurrence with the last extinction of Gs. Foraminlferos catastrophic was the mass extinction?

High oxygen content and organic flux cause eutrophic conditions. The transition from Palaeoglobigerina to Eoglobigerina implied progressive textural changes in the wall surface, such as the development of pore-pits, spines and eventually a cancellate wall.

Oxic, suboxic and dysoxic pllanctonicos were identified Table 1 based on the schemes by KaihoBaas et al. Foraminiferal paleoecology and paleoenvironmental reconstructions of the lower Miocene deposits of the Qom Formation in Northeastern Isfahan, Central Iran. New data on the Stratigraphy of the Southern Peninsula of Haiti. Reptilian diversity and roraminiferos Cretaceous-Tertiary transition in North America. The transition between Palaeoglobigerina and Eoglobigerina implied an increase of the test size, the pore diameter and the thickness of the lip, as well as the development of pore-pits, spines and, finally, cancellate walls.

Lenticulina orbicularis has been identified from middle-outer neritic to above the CCD Pezelj et al. Perspectives on the blind test. Blow emended Eoglobigerina, elevating it to generic rank and re-describing it to have a cancellate wall texture pore-pits usually with clearly defined interpore ridgesintraumbilical foraminiferod with a weakly developed porticus i. The Cibicidoides ungerinanus cluster is dominated and characterized by the predominance of eutrophic, warm water, marine salinity, highly oxygenated bottom waters, and species typical of high dissolved oxygen values High Oxic Index.

Because they are two of the most continuous and expanded lower Fkraminiferos sections known to date Molina et al. Such occurrence suggests development under open, deep marine environments middle to outer neritic zone. Academic Press, London, Textularia agglutinans and Quinqueloculina triangularis are present in the lower part whereas in the middle and upper parts of the Bagh section gradually become more scarce.

They represent two evolutionary trends within Eoglobigerinidae: Geological Society of America Special Paper, In almost all species, the thickness of the lips increases gradually and it resembles a porticus in some specimens of Parasubbotina e.

United States National Museum Bulletin, Interval from first occurrence panctonicos the zonal marker Globigerinoides primordius to the first occurrence of Globigerinoides trilobus. Some authors believed that the Oligocene-Miocene planctoncos should be established at the first evolutionary occurrence of the genus Globigerinoidesespecially the appearance of Globigerinoides primodius Blow, ; Bolli et al. No obstante, se observa un descenso de las especies cosmopolitas con respecto a las tropicales-subtropicales.

The formation is mainly represented by carbonate deposits marl, marly limestone facies and subordinate siliciclastic facies. Deccan traps mantle degassing in the terminal Cretaceous marine extinctions. The evidence for a meteorite impact at the Cretaceous-Tertiary boundary. Prever sur les Orbitoides: The second displays 3 V — 7 chambers in the last whorl with a low rate of increase in chamber size.

According to Arenillas et al. We thank Hanspeter Luterbacher, and an anonymous reviewer for helpful comments. Abundance of epifaunal biota as well as lower species diversity and higher population of this community demonstrate a highly oxic environment, warm with normal salinity. In the examined material, the Globigerinoides primordius Zone represents the oldest Miocene planktonic foraminiferal zone recorded. The most significant difference between the two species is the wall texture: Lenticulina orbicularin association with Cibicidoides sp.

The interpretation of paleosalinity in the Bagh outcrop was measured based on biota assemblages. In order for the best analysis of paleoenvironment, we used cluster modeling. This study is based on high-resolution biostra-tigraphy and an intensive search for transitional specimens between species and genera in nine lower Danian sections of Europe, the Americas and North Africa, and in the Deep Sea Drilling Project Site Shatsky Rise, North Pacific.

July 23, Corrected manuscript received: This is consistent with our proposal since they assigned primitive, non-cancellate P.








Foraminífera: características, clasificación, ciclo de vida


Related Articles