Petrological and Geochemical Investigations of Deep Sea Turbidite Sands in the Pandora and Moresby Troughs, Source to Sink Papua New Guinea Focus Area
Luke J. Patterson1, Samuel J. Bentley1, Darrell Henry1, Gerald R. Dickens2,
Andre W. Droxler2, Larry C. Peterson3, and Bradley N. Opdyke4
1 Louisiana State University, Baton Rouge, LA
2 Rice University, Houston, TX
3 University of Miami, Miami, FL
4 The Australian National University, Canberra, Australia
The Moresby and Pandora Troughs of the northern Coral Sea are components of the deep-sea depositional system that is the ultimate sink for the Source to Sink Papua New Guinea Focus Area. Cores collected from the R/V Melville during March-April 2004 reveal marine volcaniclastic and fluvial-deltaic turbidites deposited during the Late Quaternary. Constraining the spatial, temporal, and source characteristics for these terrigenous sands through mineralogical, chemical, and textural analysis is the primary focus of this study. All cores contain thin-bedded sandy turbidite packages interbedded with hemipelagic mud's and correspond to cm to m thick turbiditic sequences with the fine grained sand fraction represented in all cores. The basal turbidite sands of Moresby trough core JPC22 are composed of abundant pristine pumice fragments and glass shards, with phenocrysts (amphibole, plagioclase, biotite, pyroxene and oxides). Total alkali-silica (TAS) plots of the vitric particles are strongly rhyolytic and the calcic amphiboles all cluster as edenite. Preliminary analysis of the biotites suggests high titanium concentrations indicative of high temperature. The basal turbidites of the Pandora trough core JPC66 are predominantly quartzofeldspathic with a lesser presence of Fe-Mg silicates. Compositions of the feldspars are nearly pure albite. The contrast in mineralogy and mineral chemistry between JPC66 and JPC22 reflects contrasting source areas and fluvial delivery systems. The Moresby Trough has received secondary monomagamtic (compositional homogeneity) volcaniclastic turbidite sands derived mostly from volcanic/collision margin highlands of SE PNG, whereas the Pandora Trough has received quartzo-feldspathic sands from the Fly/Strickland system, more akin to a trailing-edge margin.