Publisher: Изд-во СО РАН, НИЦ ОИГГМ , Place of publication: Новосибирск , Уear of publication: 1996

Rich assemblages of microphytoplankton and microforaminifera were found in marine Lower Cretaceous section from the Yatria River (Subarctic Urals). Their distribution depends on the range of coastal line and depth. Consecutive changes of associations of a microphytoplankton (assemblages: Pterospermella Acritarchs-Chlamydophorella and Escharisphaeridia-Chorate dinocysts-Pterospermella in the Berriasian; Acritarchs Chlamydophorella-Pterospermella, Dingodinium-Leiosphaeridia and Escharisphaeridia-Chorate dinocysts Pterospermella in the Valanginian-Early Hauterivian; Acritarchs-Circulodinium-Escharisphaeridia, Pterospermella Acritarchs-Chlamydophorella and Escharisphaeridia-Chorate dinocysts-Pterospermella in the Early Hauterivian) and catenas of microforaminifera (assemblages: Subammoglobigerina and Subtrochammina-Ammbaculinoides in the Berriasian; Subammoglobigerina-Subtrochammina and Ammbaculinoides-Recurvoides in the Valanginian) in the Cretaceous sea of Subarctic Urals have been established. These successions reflect environmental changes from lagoonal to relatively deep-water setting. The boundaries of bionomical zones of microbenthos and microphytoplankton do not coincide, which is related to a different pattern of life and to different environmental factors controlling their distribution.