Transition from a transgressive to a regressive river-mouth sediment body in Tokyo Bay during the early Holocene: Sedimentary facies, geometry, and stacking pattern

2021 ◽  
pp. 106059
Author(s):  
Susumu Tanabe ◽  
Rei Nakashima ◽  
Yoshiro Ishihara
2020 ◽  
Vol 95 ◽  
pp. 84-96
Author(s):  
Gang Xu ◽  
Jian Liu ◽  
Marcello Gugliotta ◽  
Yoshiki Saito ◽  
Lilei Chen ◽  
...  

AbstractThis paper presents geochemical and grain-size records since the early Holocene in core ECS0702 with a fine chronology frame obtained from the Yangtze River subaqueous delta front. Since ~9500 cal yr BP, the proxy records of chemical weathering from the Yangtze River basin generally exhibit a Holocene optimum in the early Holocene, a weak East Asian summer monsoon (EASM) period during the middle Holocene, and a relatively strong EASM period in the late Holocene. The ~8.2 and ~4.4 cal ka BP cooling events are recorded in core ECS0702. The flooding events reconstructed by the grain-size parameters since the early Holocene suggest that the floods mainly occurred during strong EASM periods and the Yangtze River mouth sandbar caused by the floods mainly formed in the early and late Holocene. The Yangtze River-mouth sandbars since the early Holocene shifted from north to south, affected by tidal currents and the Coriolis force, and more importantly, controlled by the EASM. Our results are of great significance for enriching both the record of Holocene climate change in the Yangtze River basin and knowledge about the formation and evolution progress of the deltas located in monsoon regions.


Author(s):  
Hiroshi YAGI ◽  
Tanuspong POKAVANICH ◽  
Kazuo NADAOKA ◽  
Ryuichi ARIJI ◽  
Ken FURUDOI ◽  
...  

Author(s):  
Yasumitsu Mikami

Long-term shoreline changes on the marginal coast of the Banzu tidal flat in Tokyo Bay were investigated using aerial photographs. In the area immediately north of the Obitsu River mouth, the beach was eroded owing to the decrease in sand supply from the river, resulting in the exposure of a layer composed of cohesive material in the previous tidal flat, and sand was transported northward to form a sand spit at the mouth of the north tributary. In 2011, the giant tsunami generated by the Great East Japan Earthquake propagated deep into Tokyo Bay, and sand bars were pushed landward by 7 m parallel to the shoreline owing to the tsunami overflow.


Author(s):  
Ryuichi ARIJI ◽  
Hiroshi YAGI ◽  
Kazuo NADAOKA ◽  
yasuyuki NAKAGAWA ◽  
Hiroshi OGAWA ◽  
...  

2020 ◽  
Author(s):  
Matías Frugone-Álvarez ◽  
Claudio Latorre ◽  
Fernando Barreiro-Lostres ◽  
Santiago Giralt ◽  
Ana Moreno ◽  
...  

Abstract. Late Quaternary volcanic basins are active landscapes from which detailed archives of past climate, seismic and volcanic activity can be obtained. A multidisciplinary study performed on a transect of sediment cores was used to reconstruct the depositional evolution of the high-elevation Laguna del Maule (LdM) (36° S, 2180 m asl, Chilean Andes). The recovered 5 m composite sediment sequence includes two thick turbidite units (LT1 and LT2) and numerous tephra layers (23 ash and 6 lapilli). We produced an age model is based on nine new 14C AMS date, existing 210Pb and 137Cs data and the Quizapú ash horizon (CE 1932). According to this age model, early Holocene were followed by a phase of increased productivity during the mid Holocene and higher lake levels after 4.0 ka BP. Major hydroclimate transitions occurred at ca. 0.5, 4.0, 8.0 and 11 ka BP. Decreased summer insolation and winter precipitation due to a southward shift in the Southern Westerly Winds and a strengthened Pacific Subtropical High could explain early Holocene lower lake levels. Increased biological productivity during the mid-Holocene (~ 8.0 to 6.0 ka) is coeval with a warm-dry phase described for much of southern South America. Periods of higher lake productivity are synchronous to higher frequency of volcanic events. During the late Holocene, the tephra layers shows compositional changes suggesting a transition from silica-rich to silica-poor magmas at around 4.0 cal ka BP. This transition was synchronous with increased variability of sedimentary facies and geochemical proxies, indicating higher lake levels and increased moisture at LdM after 4.0 cal ka BP, most likely caused by the inception of current ENSO/PDO-like dynamics in central Chile.


2012 ◽  
Vol 518-523 ◽  
pp. 5605-5610
Author(s):  
Ling Xiao ◽  
Qin Lian Wei

LW3-1-1 located in Baiyun sag of Zhujiang River mouth basin is a potential area for oil and gas submarine Fan based on a detailed study of petrologic and paleontological assemblage characteristics. The fan have developed granular flow, sandy debris flow, low -density turbidity flow and other gravity currents along the slope. Sandy debris flow is the mainly sedimentary type of channel sand bodies of the deepwater fans, and there are also reverse grading, positive grading, parallel bedding and horizontal bedding. In addition, many liquefaction and fluidization structures and biological escape trace in graded bedding as well as abundant burrow pores and bioturbation in horizontal bedding are observed. Based on analysing sedimentary facies, the depositional model of sandy grain flow-debris flow of proximal of marine turbidity fan under the background of initial transgression is proposed for the Zhujiang Formation.


Author(s):  
Md. Masidul Haque ◽  
Manoj Kumer Ghosh ◽  
Koichi Hoyanagi

Sea-level rise and sediment supply have influenced coastal morphology and sedimentation on Bangladesh’s southwestern Ganges‐Brahmaputra‐Meghna (GBM) delta coast. Satellite images and geological core from the Haringhata coastal region were analyzed to explain the morphological changes and to understand the influences on deposits. The results derived from satellite images indicate that the southern coastline experienced a retreat that ranges between 2.3 and 2.9 km. In contrast, the eastern and western coastline advanced. The erosion and accretion ratio was 0.29 from 1977 to 1989, while the ratio was higher 2.90–4.77 from 1989 to 2020. Two sedimentary facies were identified using 130 cm thick successions. A parallel to wavy laminated bluish gray mud facies of deeper part was deposited in a marine-influenced environment. A planar to hummocky cross stratified, gray to grayish white silty sand facies of storm overwash deposits overlies the mud facies with sharp contacts. Unimodal to bimodal grain distributions of sandy sediments suggest two sources: sand derived from the beach and mud carried by adjacent tidal rivers and resuspended offshore sediment. Coastline dynamics and sedimentation of the area were influenced by inequality of accommodation and sediment supply ratio in the river mouth. This occurs due to sea-level rise and deficit in upstream water and sediment discharge. Morphological change along the southwestern GBM delta coast was not only caused by wave energy, but also by rising sea levels which shifted sediment accommodation space landward.


2008 ◽  
Vol 55 ◽  
pp. 516-520
Author(s):  
Yasuyuki NAKAGAWA ◽  
Ryuich ARIJI ◽  
Shoichi MATSUZAKA ◽  
Kazunobu MOROHOSHI ◽  
Hiroshi YAGI ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document