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Indian Southwest Monsoon Variability During the Holocene As Seen In The Northeastern Arabian Sea M.Ravichandran 1 , Anil K. Gupta 1,2 and M.K. Panigrahi 1 1 Department of Geology and Geophysics, IIT Kharagpur, Kharagpur- 721 302 2 Now at Wadia Institute of Himalayan Geology, Dehra Dun - 248 001 E-mail: ravimrcp@gmail.com; anilg@wihg.res.in; mkp@gg.iitkgp.ernet.in ABSTRACT The Holocene epoch is of great socio-economic and academic importance, marked by significant changes in the Indian monsoon as well as global climates. The Indian summer or southwest monsoon is driven by sensible heating of the Asian landmass and latent heat released from cross-equatorial moisture transport (Webster, 1987). In this study, 434 sediment samples have been analyzed for benthic foraminifera from cores SK-240/327, SK-243/I-1 and ABP, 25/03, off Gujarat in the northeastern Arabian Sea. Our goal is to reconstruct the Holocene history of the Indian monsoon. Processed dry samples containing benthic foraminifera were sieved over 150 µm size sieve, and were split into suitable aliquots of ~ 300 specimens, identified and counted. Seasonal changes in the oceanography are reflected in benthic foraminiferal productivity. Study of 206 Core Samples from SK-243/I-1, covering a length of 3.20 meters below sea floor (mbsf) and a time span of ~11 kyrs allowed identification of 166 species of benthic foraminifera belonging to 69 genera. We focused here on oceanographically important species such as Anomalina globulosa (maximum 15.63 %), followed by Uvigerina proboscidea (22.53%), Bolivina spathulata (9.38%), Gyroidinoides nitidula (17.65%), Sigmoilopsis schlumbergeri (17.55 %), Bolivina dilatata (11.04 %), Bulimina marginata (21.15 %), and Nonion cf. asterizans (24.92 %), Hyalinea balthica (8.73 %), Cancris oblongus (11.94 %), etc. The characteristic species of assemblage is Anomalina globulosa which indicates intermediate to high flux of organic matter with low oxygen deep water conditions. Uvigerina proboscidea and Bolivina spathulata indicate low oxygen, sustained flux of organic matter from high surface productivity, sluggish bottom circulation (Gupta et al., 1997). Gyroidinoides nitidula and Sigmoilopsis schlumbergeri indicate low organic carbon flux or pulsed food supply and high oxygen content of environment (Mackensen et al., 1995). Bolivina dilatata indicates high organic flux and low oxygen levels. Bulimina marginata indicates oligotrophic conditions with pulse food supply, high bottom oxygenation. Nonion cf. asterizans maintains a high abundance along with opportunistic species. Hyalinea balthica indicates high productivity, low oxygen content in bottom water (Hermelin and Shimmield, 1990). We conclude that changes in benthic foraminiferal population in the studied holes archive evidence of Southwest monsoon variability. The benthic foraminiferal data reveal that the major events occurred around ~9,000- 6000 yrs suggesting a major intensification of the Indian SW monsoon. The summer monsoon was weakest during ~ 2,500 to 1,500 yrs BP. During the Medieval Warm Period the summer monsoon strengthened whereas during the most recent climatic event, the Little Ice Age, there was a drastic reduction in the intensity of the summer monsoon. Keywords: Benthic foraminifera, Indian monsoon, Arabian Sea, Holocene. The Fourth IGCP 588: PREPARING FOR COASTAL CHANGE 15
Recognition of the Late Quaternary tectonic activity in the Pearl River Delta Zhang Ke, Yu Zhangxin Sun Yat-Sen University, Guangzhou, 510275, PR China ABSTRACT As one of the largest delta in China, most area of the Pearl River Delta only records the latest sea level rise in several tens of the Pleistocene eustacy fluctuations except for the Holocene one. Obviously neotectonic movement is a very importance factor that effect transgression and can not be neglected in discussion of the formation and evolution of the delta. However, there are no consensuses on both of the neotectonic intensity and the age of the lower transgressive unit of the delta. The major differences are active and stable for the former and MIS3 and MIS5 for the latter, respectively. The wide disparity on the time and sea level of MIS3 and MIS5 results in very different explanation on neotectonic activity of the delta. Some researchers consider that all faults in the delta area are inactive ones and that the delta is subsiding so weakly that the Holocene deposit is only compensative aggregation after erosion in glacial sea level fall. While others argue that the delta is so called the fault block one and has undergone intense tectonic movement since the latest Quaternary (since MIS3). Our investigation indicates that the neotectonic activity of different trending faults varies. Although EW faults control north boundary of the delta, they have been strongly incised by flood plain and the EW piedmont lines meandered. The thickness of Quaternary deposit changes little when crossing the EW and NE faults, implying that the landform has been eroded for a long period of time and both EW and NE faults have been quietness since latest Quaternary. NEE faults distribute alongside both of the south Panyu Platform in north delta and of the north Wugui Mountains to the south delta. Most of surface of the platform has been deeply weathered to vermiculated red soil. Vermiculated red soil has a wide range of distribution in south China, formed only once (about 700~400 ka) during entire Quaternary. It indicates a strong monsoon warm environment and relatively stable peneplain process. On the platform there are many depositional terraces, equivalent to lower marine transgression cycle of the delta, with vermiculated red soil underneath. The terraces are about 10m above mean sea level on the Panyu Platform, but the equivalent deposit becomes deeper southward in delta depositional area, illustrating both NEE faulting of the platform and southward tilting of the delta. When tracing southward to the northern South China Sea continental shelf, the Quaternary deposits thicken and number of transgression cycles increases from 2 cycles in the delta to more than 6 in continental shelf when crossing the NEE Coast Fault Zone. Compared with Quaternary sea level variation cycle, the continental shelf subsided much earlier than the delta area and records more transgression events. NEE faults in the delta area actually belong to the fault system in northern South China Sea continental shelf. 16 The Fourth IGCP 588: PREPARING FOR COASTAL CHANGE
Page 12 and 13: CONTENT Tsunami history along the c
Page 14 and 15: A Methodology to Develop a Report C
Page 16 and 17: Tsunami history along the coastline
Page 18 and 19: 2004 Tsunami and Tsunamigenic sedim
Page 20 and 21: Coastal resilience on microbial pol
Page 22 and 23: Hazard Line Mapping Of Mahadi Delta
Page 24 and 25: Millennial-scale records of North A
Page 28 and 29: Coastal wind climate, coastal dunes
Page 30 and 31: Benthic Foraminifera and siltation
Page 32 and 33: Wetland Ecosystem of Mahanadi Delta
Page 34 and 35: pollen and charcoal concentration,
Page 36 and 37: Palaeo-environmental reconstruction
Page 38 and 39: Vulnerable Deltas of Indian Coast P
Page 40 and 41: The Coastal and Marine Tourism of E
Page 42 and 43: Mangroves and Coastal Changes in In
Page 44 and 45: Investigating inter--‐annual and
Page 46 and 47: High Resoluation Holocene Climatic
Page 48 and 49: Geochemical characteristics of surf
Page 50 and 51: Seawater Intrusion Due to Temporal
Page 52 and 53: Mineral magnetic study of coastal s
Page 54 and 55: Phosphorus dynamics of water - sedi
Page 56 and 57: Evaluation of major hydrogeochemica
Page 58 and 59: A Methodology to Develop a Report C
Page 60 and 61: Seaweeds culture and its impacts on
Page 62 and 63: An Environment Management Plan In A
Page 64 and 65: Subsurface Geomorphological Study o
Page 66 and 67: Morphosedimentary evidences of rapi
Page 68 and 69: Hydrogeochemical assessment of huma
Page 70 and 71: Sea Surface Height (SSH)-based Pote
Page 72 and 73: Tropical storm off Myanmar coast sw
Page 74 and 75: Integrated approach for assessment
Page 76 and 77:
Need for evolutionary studies in An
Page 78 and 79:
Integrated Coastal Zone Management
Page 80 and 81:
Assessment Over Impacts Of Sealevel
Page 82 and 83:
Holocene sea-level changes in the c
Page 84 and 85:
Evidence of Holocene flooding-storm
Page 86 and 87:
Study of Wave Parameters along the
Page 88 and 89:
Shore Specific Sediment Characteris
Page 90 and 91:
occurrences of microfossils. In the
Page 92 and 93:
Vulnerability assessment of the sou
Page 94 and 95:
Artificial Coastal Lakes (Paleo-lag
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Conference program and abstracts - Coastal-Change.Org

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