Abstract—Mollusk migrations of various intensity in the Kimmeridgian to Valanginian time span were estab-
lished in the Boreal Atlantic (West and East European Provinces), Boreal Pacific (Chukotka-Canadian and Boreal Pacific Provinces), and Arctic Realms of the Panboreal Superrealm. According to intensity degree, the migrations are classified as expansions, i.e., mass migrations, and influence migration...
| Main Authors: | , |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2000
|
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.543.7629 http://www.rogovm.narod.ru/zakharov_rogov_2003.pdf |
| Summary: | lished in the Boreal Atlantic (West and East European Provinces), Boreal Pacific (Chukotka-Canadian and Boreal Pacific Provinces), and Arctic Realms of the Panboreal Superrealm. According to intensity degree, the migrations are classified as expansions, i.e., mass migrations, and influence migrations, i.e., penetration of sep-arate taxa. Migrations of the cross- and unidirectional types are distinguished according to directions of taxa exchange. Mollusks (ammonites, belemnites, and bivalves) are subdivided into Tethyan and Boreal forms, which inhabited areas south of 45°N, and north of 50°N, respectively. Low-boreal mollusks distinguished among the latter were characteristic of an ecotone between the Panboreal and Tethy s-Panthalassa Superrealms, and Boreal-Arctic taxa dwelt north of 60°N. The ecotone of the Boreal Atlantic Realm was situated between 50 ° and 55°N. The ecotone zone persistently existed in the Boreal Pacific Realm. The ammonite ecotone of the Chukotka-Canadian Province (Primor'e) was between 45 ° and 55°N. In the Boreal Pacific Province (northern California), an ecotone of the Tithonian-Valanginian time was located between 40 ° and 50°N. Water tempera-ture lower in the north was the major factor that influenced Boreal-Tethyan migrations and positioning of bio-geographic ecotones. The coincidence of transgression peaks with the ammonite migration events is character-istic only of the Kimmeridgian-Middle Volgian time, when northward migrations of the Tethyan ammonites coincided with sea level rises. The Berriasian expansion of berriasellids to the Central Russian Sea was not |
|---|