TY - JOUR

T1 - Palynologie de la transition du Jurassique inférieur à moyen dans le nord du Caucase (sud-ouest de la Russie) calibrée par les indices biostratigraphiques dérivés des cortèges d'ammonites

AU - Goryacheva, Аnna A.

AU - Mitta, Vasily V.

AU - Riding, James B.

N1 - Publisher Copyright: © 2021 Elsevier Masson SAS

PY - 2021/10

Y1 - 2021/10

N2 - Palynomorphs from the Toarcian and Aalenian Djigiat Formation of Karachay-Cherkessia in the Kuban River Basin (North Caucasus, southwest Russian Federation) are reported for the first time. Five samples carefully selected for their biostratigraphical content were studied to document the palynological assemblages. Four samples (1, 2, 3, 4) were collected from pieces of rock with key index ammonite specimens, and sample 5 comprises fragments of ammonite shells from a sideritic concretion. Three of these samples (4, 2 and 1) yielded relatively abundant and diverse aquatic microplankton (acritarchs, dinoflagellate cysts, prasinophytes and zygnematalean algae) and terrestrial palynomorphs (pollen and spores); the remaining two samples (3 and 5) were less productive and contained fewer than 50 palynomorph specimens. The study of the dinoflagellate assemblages provided characteristic and key information. These are the uppermost Toarcian Nannoceratopsis Assemblage and the uppermost Toarcian to lowermost Aalenian Parvocysta Suite Assemblage. The former is overwhelmingly dominated by Nannoceratopsis with sparse numbers of the Parvocysta suite, and the latter yielded more diverse and common specimens of Parvocysta and its relatives. This is consistent with the hypothesis that the Parvocysta suite migrated from the Boreal Realm further south into Laurasia during the Toarcian. Certain dinoflagellate cysts such as Mancodinium semitabulatum and Scriniocassis spp., which are typical of Europe and much of Greater Laurasia are absent. Composition of the pollen and spores proved relatively out to be monotonous, and cannot be subdivided. However, in general, the composition of the assemblages of spores and pollen is consistent with the Toarcian–Aalenian transition.

AB - Palynomorphs from the Toarcian and Aalenian Djigiat Formation of Karachay-Cherkessia in the Kuban River Basin (North Caucasus, southwest Russian Federation) are reported for the first time. Five samples carefully selected for their biostratigraphical content were studied to document the palynological assemblages. Four samples (1, 2, 3, 4) were collected from pieces of rock with key index ammonite specimens, and sample 5 comprises fragments of ammonite shells from a sideritic concretion. Three of these samples (4, 2 and 1) yielded relatively abundant and diverse aquatic microplankton (acritarchs, dinoflagellate cysts, prasinophytes and zygnematalean algae) and terrestrial palynomorphs (pollen and spores); the remaining two samples (3 and 5) were less productive and contained fewer than 50 palynomorph specimens. The study of the dinoflagellate assemblages provided characteristic and key information. These are the uppermost Toarcian Nannoceratopsis Assemblage and the uppermost Toarcian to lowermost Aalenian Parvocysta Suite Assemblage. The former is overwhelmingly dominated by Nannoceratopsis with sparse numbers of the Parvocysta suite, and the latter yielded more diverse and common specimens of Parvocysta and its relatives. This is consistent with the hypothesis that the Parvocysta suite migrated from the Boreal Realm further south into Laurasia during the Toarcian. Certain dinoflagellate cysts such as Mancodinium semitabulatum and Scriniocassis spp., which are typical of Europe and much of Greater Laurasia are absent. Composition of the pollen and spores proved relatively out to be monotonous, and cannot be subdivided. However, in general, the composition of the assemblages of spores and pollen is consistent with the Toarcian–Aalenian transition.

KW - Ammonites

KW - Biostratigraphy

KW - Lower–Middle Jurassic transition

KW - North Caucasus

KW - Palynomorphs

KW - Southwest Russia

UR - http://www.scopus.com/inward/record.url?scp=85109460377&partnerID=8YFLogxK

U2 - 10.1016/j.revmic.2021.100517

DO - 10.1016/j.revmic.2021.100517

M3 - Article

AN - SCOPUS:85109460377

VL - 72

JO - Revue de Micropaleontologie

JF - Revue de Micropaleontologie

SN - 0035-1598

M1 - 100517

ER -