Coastal progradation associated with sea-level oscillations in the later phase of the Last Interglacial period, central Japan
Coastal progradation associated with sea-level oscillations in the later phase of the Last Interglacial period, central Japan
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日本中部末次间冰期后期与海平面振荡相关的海岸退化
DOI：
10.1016/j.quascirev.2022.107507
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发表时间：
2022
影响因子：
4
通讯作者：
Tamura Toru
中科院分区：
文献类型：
--
作者：
Okazaki Hiroko;Nara Masakazu;Nakazato Hiroomi;Furusawa Akira;Ito Kazumi;Tamura Toru
海洋氧同位素阶段 (MIS) 5c 和 5a 次要海平面高位的地层记录是晚更新世海平面和古环境的宝贵档案，但在硅质碎屑沿海系统中的识别率低于 MIS 5e 高位。在日本中部的关东平原，饭冈阶地包括隆起的末次间冰期（MIS 5）海洋阶地的向海边缘。 Iioka 台地的沉积学特征、红外后红外刺激发光 (pIRIR) 测年以及火山灰和古生物学分析可以识别出在 MIS 5c 和 5a 期间进展到上新世-更新世基底的波浪主导的沿海沉积系统。沿海沉积物的 pIRIR 年龄范围为 ca. 80 至 112 ka，定义了向海的年轻化趋势，这通过台地表面向海的降低得到了证实。在向海部分的露头中，在火山灰层On-Pm1（95.7 ka）上方和下方获得了两个pIRIR年龄，支持了pIRIR年代学的总体有效性。向陆部分的滩相标高（距现海平面约 53 m）突然降低（至约 37 m），并进一步被向海部分的河流切割所截断。 pIRIR 年龄包含无法区分 MIS 5c 和 5a 的不确定性。然而，中部和临海部分之间的海滩高度突然且巨大的差距表明 MIS 5c 和 5a 之间存在轻微不整合；当代的抬升可能是造成这一差距的原因。因此，Iioka阶地被解释为代表末次间冰期后期受相对海平面变化控制的沉积层序的连续下倾增生。饭冈台地的精细表征允许重新评估该地区的构造抬升率，约为0.7 毫米/年，是假设沉积物与 MIS 5e 相关的速率的两倍。如果像这里所进行的那样详细描述边缘海洋阶地的特征，那么其他地方也可能出现这种细化。
Stratigraphic records of minor sea-level highstands in Marine Oxygen Isotope Stage (MIS) 5c and 5a are valuable archives of late Pleistocene sea levels and paleoenvironments, but have been identified less commonly in siliciclastic coastal systems than the highstand of MIS 5e. In the Kanto Plain, central Japan, the Iioka terrace comprises the seaward margin of the uplifted Last Interglacial (MIS 5) marine terrace. Sedimentological characterization, post-infrared infrared stimulated luminescence (pIRIR) dating, and tephra and paleontological analyses of the Iioka terrace allow identification of a wave-dominated coastal sedimentary system that prograded onto the Pliocene-Pleistocene basement during MIS 5c and 5a. The pIRIR ages of the coastal deposits range from ca. 80 to 112 ka and define a seaward younging trend, which is corroborated by the seaward lowering of the terrace surfaces. In an outcrop in the seaward part, two pIRIR ages were obtained above and below the tephra layer On-Pm1 (95.7 ka), supporting the general validity of the pIRIR chronology. The elevation of beach facies in the landward part (ca. 53 m above the present sea level) abruptly lowers (to ca. 37 m) and is further truncated by fluvial incision in the seaward part. The pIRIR ages include uncertainties that prevent distinction between MIS 5c and 5a. However, the abrupt and large gap in the beach levels between the central and seaward parts suggests the presence of a minor unconformity between MIS 5c and 5a; contemporary uplift may account for the gap. The Iioka terrace is thus interpreted as representing the successive downdip accretion of depositional sequences controlled by relative sea-level changes in the later Last Interglacial period. The refined characterization of the Iioka terrace allows reevaluation of the tectonic uplift rate of this area as ca. 0.7 mm/yr, twice the rate assuming correlation of the deposits with MIS 5e. Such refinement is likely elsewhere if marginal marine terraces are characterized in detail, as carried out here.