Results of micropaleontological examination and age of dredge samples collected from the lower slopes of the Kuril Basin, Sea of Okhotsk

An integrated (petrographical and micropaleontological) study of sedimentary cover samples dredged from the lower slopes of the Kuril deep-sea basin was carried out. Pliocene-Pleistocene sediments are mainly represented by tuffaceous sedimentary rocks (tuffites, tuffaceous muds, tuffaceous diatomites, tuffaceous silts, tuffaceous sandstones, etc.). Significant admixtures of pyroclastic matter, especially of volcanic glasses, indicates that sedimentation process was accompanied by explosive volcanism. The data obtained give evidence about intensification of tectonomagmatic regime within the region under study during Pliocene-Pleistocene time. By the beginning of Pliocene, a deep-sea basin with a well-manifested continental and/or island slope and a narrow shelf already existed. Pliocene-Pleistocene deposits accumulated in a cold well-aerated deep-sea basin under oxic conditions and downslope sediment transport.

本研究对疏浚采集自千岛深海盆（Kuril deep-sea basin）下斜坡的沉积盖层样品，开展了岩石学（Petrography）与微古生物学（Micropaleontology）一体化综合研究。上新世-更新世（Pliocene-Pleistocene）沉积物主要由凝灰质沉积岩（tuffaceous sedimentary rocks）构成，涵盖凝灰岩、凝灰质泥岩、凝灰质硅藻岩、凝灰质粉砂岩、凝灰质砂岩等类型。样品中赋存大量火山碎屑物质（pyroclastic matter），尤以火山玻璃（volcanic glasses）为主要组分，表明沉积过程伴随有爆炸性火山活动（explosive volcanism）。本次研究所获数据证实，研究区域在该时段的构造岩浆活动体制（tectonomagmatic regime）强度显著增强。至上新世初期，研究区域已形成兼具清晰发育陆坡（continental slope）与岛坡（island slope）、且陆架（shelf）狭窄的深海盆地。上新世-更新世沉积物堆积于寒冷、充分充氧的氧化环境（oxic conditions）深海盆地中，沉积搬运以坡移沉积作用（downslope sediment transport）为主。