Holocene filling of a narrow estuary in a regressive coast: The Paleo-Kinu Bay region, central Japan
Holocene filling of a narrow estuary in a regressive coast: The Paleo-Kinu Bay region, central Japan
复制标题
全新世海退海岸狭窄河口的充填：日本中部古鬼怒湾地区
DOI：
10.1016/j.margeo.2022.106795
复制
发表时间：
2022
期刊：
影响因子：
2.9
通讯作者：
Mizuno Kiyohide
中科院分区：
文献类型：
--
作者：
Tanabe Susumu;Nakashima Rei;Mizuno Kiyohide
河口湾是海进海岸的典型沉积体系;然而，海退海岸上也存在具有类似几何形状的沉积体系。在亚洲、南美洲和澳大利亚等地发现了这种“海退河口”，这些地区自全新世中期以来经历了相对的海平面下降。海退河口形成于下切的山谷中，这些山谷被最后一次冰消期的海平面上升淹没，并接受相对较少的河流泥沙排放。日本最大的河口，长120公里，宽10公里，位于古基努湾地区。在世纪，在人工改道的通河之前，该地区开发了一个部分未填充的波浪主导的河口。在这项研究中，我们记录的14个沉积物芯和171放射性碳测年的基础上，全新世填充的古基努湾。7- 4ka的无填充波控河口比4-0 ka具有更明显的波浪建造形态要素。4-0 ka时，由于海平面下降和潮流减弱，湾口被桑迪潮河沉积物侧向加积而变窄，中央海盆被泥质湾头三角洲沉积物充填。湾口变窄和中央盆地填充的加速类似于发生在4-0 ka的古基努湾地区还没有确定在海侵河口，但海退河口的共同特点。
Estuaries are typical depositional systems of transgressive coasts; however, depositional systems with similar geometry also occur on regressive coasts. Such “regressive estuaries” are found in areas of Asia, South America, and Australia that have experienced relative sea-level lowering since the middle Holocene. Regressive estuaries form in incised valleys that were drowned by the last deglacial sea-level rise and receive relatively little riverine sediment discharge. The largest estuary in Japan, with a length of 120 km and a width of 10 km, is in the Paleo-Kinu Bay region. A partly unfilled wave-dominated estuary developed in this region prior to the artificial diversion of the Tone River during the 17th century. In this study, we document the Holocene filling of the Paleo-Kinu Bay on the basis of 14 sediment cores and 171 radiocarbon dates. Unfilled wave-dominated estuary at 7–4 ka has more pronounced wave-built morphologic elements than at 4–0 ka. As a result of sea-level lowering and weakening of tidal currents at 4–0 ka, the bay mouth became narrowed by lateral accretion of sandy tidal river sediments and the central basin was filled by progradation of muddy bayhead delta sediments. The acceleration of the bay mouth narrowing and central basin infilling similar to what happened during 4–0 ka in the Paleo-Kinu Bay region have not been identified in transgressive estuaries, but are common features of regressive estuaries.