Holocene Palynology of the Gulf of Papua, Papua New Guinea: Using Modern Palynomorph Distribution to Better Constrain Paleoenvironmental Changes

Abstract

Multiple NSF (National Science Foundation)-funded MARGINS Source-to-Sink cruises were conducted in the Gulf of Papua (GoP), Papua New Guinea (PNG), from 2003 through 2005 to better understand how sediment is created, transported, and deposited. Although much work has been done on the data collected during these cruises, palynological analysis has never been conducted on the hundreds of available cores. The first phase of this project (Chapters 2 and 3) examines the connection between modern depositional regimes in the GoP and species assemblages recovered. Statistical analysis of palynomaceral assemblages (Chapter 2) indicates a correlation between their distribution and bathymetry, sedimentation rate, and distance from shore. In particular, wood and cuticular material is found closer to shore and in areas with higher sedimentation rates, while SOM increases in abundance with increasing distance from shore and lower sedimentation rates. Characteristic palynomaceral assemblages appear in certain major depositional environments. Palynomorph assemblages (Chapter 3) also indicate a clear correlation with bathymetry, sedimentation rate, and distance from shore. Major groups found in palynological slides reflect the composition of vegetation on mainland PNG. Reworked palynomorphs also provide an indication of sediment source (e.g., from the Ok Tedi mine on the mainland), but this is complicated, because many ages of reworking (e.g., a mix of Cretaceous, Paleogene, Neogene, and Recent palynomorphs) are found in samples. The second phase of this project (Chapter 4) includes a paleoenvironmental reconstruction of the last ~14.5 kyr in the GoP. Three long cores (MD-50, MV-41, MV-46) were selected for this analysis. Changes in palynomorph assemblages allow delineation of four major climate intervals from 14.5 kyr to present, including the Bølling-Allerød Interstadial (14.5 to 12.5 kyr BP), the Younger Dryas (12.5 to 11.5 kyr BP), Meltwater Pulse-1B (11.5 to 10.5 kyr BP), and the Holocene (10.5 kyr BP to present). Results indicate that mangrove pollen and marine indicators clearly delineate the end of the transgression between 5 to 6 kyr BP Palynomorph data and oxygen-18 isotopes from MD-50 also indicate an increase in El Niño Southern Oscillation (ENSO) activity at approximately 5 kyr BP.