Pleistocene Climatic Changes as Deduced from a Pollen Analysis of Site 717 Cores

Yasuda, Yoshinori; Amano, Kazuo; Yamanoi, Tohru

doi:10.2973/odp.proc.sr.116.130.1990

Cited by 4 publications

(8 citation statements)

References 5 publications

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“…Savanna was widespread within flood plains (Quade et al . 1989) and probably also in terra firma areas, as suggested from the abundance of Poaceae pollen in distal Bengal Fan sediments (Yasuda et al 1990), which represent pollen sourced from the entire Ganges catchment. Savanna is also found in Indochinese seasonal fire-prone lower montane forests which are dominated by Pinus kesiya or P. roxburghii , and occasionally P. merkusii.…”

Section: Late Neogene Cooling and Drying And Expansion Of C4 Grasslandsmentioning

confidence: 96%

“…Natural savanna of the African type, which is sustained by browsing mammals, is rare in India today, but was probably widespread prior to the influence of hominids, who may have eliminated several of the large mammals (Patnaik 2015) that characterized the Pliocene. Savanna was widespread within flood plains (Quade et al 1989) and probably also in terra firma areas, as suggested from the abundance of Poaceae pollen in distal Bengal Fan sediments (Yasuda et al 1990), which represent pollen sourced from the entire Ganges catchment. Savanna is also found in Indochinese seasonal fire-prone lower montane forests which are dominated by Pinus kesiya or P. roxburghii, and occasionally P. merkusii.…”

Section: Late Neogene Cooling and Drying And Expansion Of C4 Grasslandsmentioning

confidence: 97%

“…data.Perning, East Java, palynological analysis R. J and H. P. Morley unpublished in Huffman & Zaim (2003). Bengal Fan (Yasuda et al 1990). …”

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confidence: 99%

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Assembly and division of the South and South-East Asian flora in relation to tectonics and climate change

2018

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Abstract:The main phases of plant dispersal into, and out of the South-East Asian region are discussed in relation to plate tectonics and changing climates. The South-East Asian area was a backwater of angiosperm evolution until the collision of the Indian Plate with Asia during the early Cenozoic. The Late Cretaceous remains poorly understood, but the Paleocene topography was mountainous, and the climate was probably seasonally dry, with the result that frost-tolerant conifers were common in upland areas and a low-diversity East Asian aspect flora occurred at low altitudes. India's drift into the perhumid low latitudes during the Eocene brought opportunities for the dispersal into South-East Asia of diverse groups of megathermal angiosperms which originated in West Gondwana. They successfully dispersed and became established across the South-East Asian region, initially carried by wind or birds, beginning at about 49 Ma, and with a terrestrial connection after about 41 Ma. Many Paleocene lineages probably went extinct, but a few dispersed in the opposite direction into India. The Oligocene was a time of seasonally dry climates except along the eastern and southern seaboard of Sundaland, but with the collision of the Australian Plate with Sunda at the end of the Oligocene widespread perhumid conditions became established across the region. The uplift of the Himalaya, coinciding with the middle Miocene thermal maximum, created opportunities for South-East Asian evergreen taxa to disperse into north India, and then with the late Miocene strengthening of the Indian monsoon, seasonally dry conditions expanded across India and Indochina, resulting eventually in the disappearance of closed forest over much of the Indian peninsula. This drying affected Sunda, but it is thought unlikely that a ‘savanna’ corridor was present across Sunda during the Pleistocene. Some dispersals from Australasia occurred following its collision with Sunda and following the uplift of New Guinea and the islands of Wallacea, Gondwanan montane taxa also found their way into the region. Phases of uplift across the Sunda region created opportunities for allopatric speciation and further dispersal opportunities. There is abundant evidence to suggest that the Pleistocene refuge theory applies to the South-East Asian region.

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Section: Late Neogene Cooling and Drying And Expansion Of C4 Grasslandsmentioning

confidence: 96%

Section: Late Neogene Cooling and Drying And Expansion Of C4 Grasslandsmentioning

confidence: 97%

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Assembly and division of the South and South-East Asian flora in relation to tectonics and climate change

2018

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“…Pollen from the Siwalik Formation indicate the Miocene appearance of xeric and halophilic shrubs (Amaranthaceae and Chenopodaceae) (39). Those taxa are also represented along with Euphorbiaceae pollen in the last 1 My in the distal Bengal Fan, south of Sri Lanka (46). However, the C 4 pathway is most prevalent within tropical grasses in the catchment today, and tall grasses are therefore also assumed to be the most likely source of C 4 "wood" delivered in the last 5 My.…”

Section: Expansion In the G-b Catchment And Wood Sourcingmentioning

confidence: 99%

Sustained wood burial in the Bengal Fan over the last 19 My

Lee

Galy

Feng

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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The Ganges–Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the world’s largest active sedimentary deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO2. While much attention has been paid to organic-rich fine sediments, coarse sediments have generally been overlooked as a locus of organic carbon (OC) burial. However, International Ocean Discovery Program Expedition 354 recently discovered abundant woody debris (millimeter- to centimeter-sized fragments) preserved within the coarse sediment layers of turbidite beds recovered from 6 marine drill sites along a transect across the Bengal Fan (∼8°N, ∼3,700-m water depth) with recovery spanning 19 My. Analysis of bulk wood and lignin finds mostly lowland origins of wood delivered episodically. In the last 5 My, export included C4 plants, implying that coarse woody, lowland export continued after C4 grassland expansion, albeit in reduced amounts. Substantial export of coarse woody debris in the last 1 My included one wood-rich deposit (∼0.05 Ma) that encompassed coniferous wood transported from the headwaters. In coarse layers, we found on average 0.16 weight % OC, which is half the typical biospheric OC content of sediments exported by the modern G-B Rivers. Wood burial estimates are hampered by poor drilling recovery of sands. However, high-magnitude, low-frequency wood export events are shown to be a key mechanism for C burial in turbidites.

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“…It is considered as an allochtonous pollen, related to plants recorded in central Africa, Ethiopia and Sudan (Erikson, 1964;Saad and Sami, 1967). Furthermore, they are considered as one of the typical species of the southern Hemisphere (Yasuda et al, 1990). Hence, the presence of Podocarpus supports that Nile water was reaching the area under study, carrying these pollens.…”

Section: Palaeovegetation Interpretation and Inferred Depositional Enmentioning

confidence: 97%

Palynology and palaeovegetation reconstruction in late Quaternary sediments of the southern Suez Isthmus, Egypt

Kholeif

2004

Journal of African Earth Sciences

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Pleistocene Climatic Changes as Deduced from a Pollen Analysis of Site 717 Cores

Cited by 4 publications

References 5 publications

Assembly and division of the South and South-East Asian flora in relation to tectonics and climate change

Assembly and division of the South and South-East Asian flora in relation to tectonics and climate change

Sustained wood burial in the Bengal Fan over the last 19 My

Palynology and palaeovegetation reconstruction in late Quaternary sediments of the southern Suez Isthmus, Egypt

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