Dinoflagellate cyst record and paleoceanography through the Pliocene–Pleistocene transition at ODP Site 1143, southern South China Sea

Palynological analysis of 72 samples from Ocean Drilling Program (ODP) Site 1143, southern South China Sea, spanning a 2.90–2.41 Ma interval across the Pliocene–Pleistocene boundary, reveals a well preserved and relatively diverse dinoflagellate cyst (dinocyst) record. Generally, the cysts of phototrophic (gonyaulacoid) taxa increased during interglacials whereas those of heterotrophic (protoperidinioid) taxa increased during glacials, particularly around the pronounced glacial stages MIS G6, 104 and 100. Increases of these heterotrophic taxa during glacials are consistent with 1) reduced sea-surface salinity, 2) increased nutrient levels and hence surface-water productivity due to increased river input, 3) increased sediment accumulation rate as a result of increased fluvial erosion inferred to aid the rapid burial and preservation of these heterotrophic taxa, and 4) increased winter monsoon intensity inferred to facilitate the physical erosion and transport of sediments. Terrestrial palynomorphs generally increase in abundance during the glacials and decline during the interglacials, interpreted as reflecting increased erosion and river runoff due to lowered sea level and enhanced winter monsoon during glacial stages. Strong correlation exists between the dinocyst taxa recorded in this study and published proxy data from this study site. Species score distributions produced by correspondence analysis implies strong influence of trophic conditions on the distribution of the dinocyst taxa. Notable warm-water dinocyst taxa Edwardsiella sexispinosa, Hystrichokolpoma rigaudae, Hystrichokolpoma spp., Invertocysta tabulata and Operculodinium bahamense identified in this study were not recorded from the same interval in a recently published investigation of the Sea of Japan / East Sea. In addition, Edwardsiella sexispinosa extends later in the present study (2.48 Ma) than previously recorded (2.81 Ma in the western North Atlantic) which may reflect the influence of the Western Pacific Warm Pool. This is the first study of dinocysts and acritarchs spanning the Pliocene–Pleistocene boundary in the South China Sea, and also appears to be the first record of Edwardsiella sexispinosa, Invertocysta tabulata and Operculodinium bahamense from the Pacific region.

Name thesis:degree_name

M.Sc. Earth Sciences

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Faculty of Mathematics and Science

Department dc:contributor.department

Department of Earth Sciences

Grantor

Brock University

Year dc:date.issued

2022

Author dc:creator

• Okafor, Onyinye Sandra

• Dinoflagellate cysts
• East Asian Monsoons
• Pliocene–Pleistocene
• South China Sea
• ODP Site 1143

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10464/16552

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/16552