A clay mineral provenance study of the northern Pandora Trough continental margin, Gulf of Papua

X-ray diffraction mineralogy of western-, central-, and eastern-derived fluvial sediments within the Gulf of Papua exhibits distinct and mixed clay mineral assemblages. These mineral assemblages allow for a better understanding of how a thick muddy continental margin shelf-edge depocenter in the eastern Gulf of Papua of latest Pleistocene/early Holocene age formed, as well as connections between terrestrial sediment delivery and evolution of deep-sea deposits in this region. Modern clay mineralogy reveals a high to low gradation of illite/smectite values from the western to eastern Gulf of Papua (Slingerland et al., 2008a), which is applied to the recent past for provenance indications within this study. The shelf-edge depocenter, at the MV-41 core location, analyzed in this study formed during the Bølling-Allerød/Younger Dryas when the shoreline was located \u3c 10 km landward of the modern shelf-edge and mass accumulation rates were high, thus allowing for minimal illite/smectite-dominated sediment input from the western and central GoP. However, modern X-ray diffraction data show a higher kaolinite/chlorite input, indicative of a more local, volcanic source, potentially within the Lakekamu River catchment. This mineral assemblage is distinct from the higher illite/smectite and lower kaolinite/chlorite signatures within the upper/middle slope cores, MV-46 and MV-49, and is consistent with modern central Gulf of Papua surficial clay mineralogy being Purari River-derived. This analysis of clay-rich mud provenances, in conjunction with other analyses, provides an improvement of understanding modern mudflow, and potentially the paleogeographical extent of clay-rich muds in unconventional shale plays

Petrological and geochemical investigations of deep sea turbidite sands in the Pandora and Moresby Troughs: Source to Sink Papua New Guinea Focus Area

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 (PNG) Focus Area. Cores collected from the R/V Melville during March-April 2004 reveal marine volcaniclastic and terrigenous turbidites deposited in these troughs during the Quaternary. Constraining the spatial, temporal, and provenance characteristics for these terrigenous sands through mineralogical, chemical, and textural analysis is the primary focus of this study. All cores contain thinly-bedded sandy turbidite packages interlayered with hemipelagic marls and typical centimeter-to-meter-thick turbidite sequences. The Moresby Trough core JPC22 appears to be generally finer-grained then the Pandora trough core JPC 66. Typical QFL percentages from JPC22 are 13:65:23, respectively, and plagioclase/ total feldspar ratios are near 0.90. These basal turbidite sands contain well-preserved rhyolitic pumice fragments and glass shards, with phenocrysts of amphibole, plagioclase, biotite, pyroxene and oxides. Typical QFL percentages from Pandora Trough core JPC66 are 69:14:17, and plagioclase / total feldspar ratios are near 0.47. These basal turbidite sands are predominantly quartzofeldspathic with a significant amount of heavy minerals (zircon, amphibole and oxides). The contrast in submarine sand mineralogy and mineral chemistry between 66JPC and 22JPC reflects distinct sedimentary sources composed of both fluvial and volcaniclastic material. The Moresby Trough has received secondary monomagmatic volcaniclastic turbidite sands derived mostly from volcanic/collision margin highlands of SE PNG, and the Pandora Trough has received quartzo-feldspathic sands from the Fly/Strickland system, more akin to a trailing-edge margin. Mineral textures and chemistry suggests minimal associations between sand bodies, and may represent isolated basins controlled by complex sea-floor bathymetry and episodic turbidity flows from diverse sources. The signature of the adjacent submarine fan deposits may aid the interpretation of continental margin growth as a function of sediment flux, sediment source, and dispersal pathways. These deposits may also give insight into the evolution of volcanic island arcs on longer time scales. This investigation concludes that the Pandora and Moresby trough turbidite sand bodies record varying sediment sources and somewhat isolated volcanic events contributing to the evolution of the southern PNG continental margin

Paleoceanography of the Gulf of Papua using multiple geophysical and micropaleontological proxies

Recent marine and late Pleistocene sediments examined from the Gulf of Papua (GoP), Papua New Guinea investigate the flux and fate of detrital sediments and organic carbon over the last glacial-interglacial cycle. Based on surface sediment magnetic susceptibility (MS) and calcium carbonate concentrations, recent marine sediment is exported off the narrow shelf and into deeper regions via the Kerema Canyon of the northern Pandora Trough. Detrital clastic sediment is then dispersed deeper into the central and southern Pandora Trough. Except for pelagic deposition, very little detrital material reaches the Ashmore Trough and Eastern Plateau adjacent to the Great Barrier Reef. Rock-Eval pyrolysis data and organic petrography indicate that late Pleistocene and recent organic matter were strongly degraded prior to burial. Late Pleistocene depositional records come from two, 12 m piston cores retrieved from the slope of the northern Pandora Trough. MV-54 was taken at the mid-slope of the central Pandora Trough (923 m) and MV-51 was collected from a bathymetric high in the northeastern Pandora Trough (804 m). Core sediments were analyzed with MS, calcium carbonate, organic geochemistry, and benthic foraminiferal assemblages. Both cores show two periods of rapid sediment accumulation. High accumulation rates characterize 15,800-17,700 Cal. yrs B.P. in MV-54 and correspond to the early transgression when rivers delivered sediments closer to the shelf-edge. Benthic foraminiferal assemblages in MV-51 indicate a seasonally variable flux of organic carbon during late LGM (~18,400-20,400 Cal. yrs B.P.), suggesting enhanced contrast between monsoon seasons. The oldest section, \u3e32,000 14C yrs B.P., contains the highest mass accumulation rates and TOC fluxes, with \u3e50% of the organic carbon derived from C3 vascular plant matter. MS and benthic foraminiferal accumulation rates are orders of magnitude higher during this interval than any younger time indicating a greater influence of detrital minerals and labile organic carbon. Because mineralogy and detrital input are shown to be the main controls on MS variability, the MS data in this interval suggest more direct dispersal pathways from central and eastern PNG Rivers to the core site when sea level was lower and dispersal gradients were higher

Sedimentation on a mixed siliciclastic/carbonate continental margin over decadal to millennial timescales: Gulf of Papua

Sediments from the Gulf of Papua were examined to estimate particle flux and sediment mass accumulation rates on multiple timescales. Patterns of sediment mass accumulation and inventory-derived 210Pb fluxes display regional variations, decreasing seaward, and along isobaths seaward from the northeastern shelf edge. The amount of terrigenous sediment load being discharged annually from the shelf and accumulating in Pandora Trough is approximately 7-14×106 tonnes. The existence of possible turbidity-current transport and deposition have been documented in deeper parts of the Gulf of Papua. High excess 210Pb fluxes estimated from seabed inventories at the shelf edge and upper slope are consistent with the combined effects of sediment focusing and boundary scavenging of oceanic water masses. Sediments may be transported from inner-shelf depocenters by oceanic processes, focused in depocenters near the northeastern Gulf of Papua shelf edge, and distributed downslope through a combination of nepheloid-layer flow and possible turbidity-currents. For the cores located between shelf edge and lower slope, biodiffusion coefficients and mixing depths exhibit a decreasing trend with increasing water depth. Using a two-layer model, biodiffusion coefficients in these cores are in the range of 0.007-60 cm2 y-1 for the upper layer and 0.002-2.9 cm2 y-1 for the bottom layer. Sediment mass accumulation rates without the influence of physical mixing are probably overestimated by a factor of ~1.4. Jumbo piston cores taken from the shelf edge and upper and middle slope in the northern Pandora Trough suggest variation in sediment mass accumulation rates during post-Last Glacial Maximum (LGM) sea level rise. Upper 12 m of the sediment on the northeastern shelf edge has deposited in \u3c 12 ky BP after post-LGM sea level rise. The bulk of this mud deposit, with mass accumulation rates as high as 3900 g cm-2 ky-1, is constrained between the time of Last Glacial Maximun and Younger Dryas. The findings from this study suggest that physical processes building the mud wedge on the northeastern Gulf of Papua shelf were similar to the physical processes acting today building the clinoform in the western Gulf of Papua shelf

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

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

Zircon U-Pb age constraints on NW Himalayan exhumation from the Laxmi Basin, Arabian Sea

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zhou, P., Stockli, D. F., Ireland, T., Murray, R. W., & Clift, P. D. Zircon U-Pb age constraints on NW Himalayan exhumation from the Laxmi Basin, Arabian Sea. Geochemistry Geophysics Geosystems, 23(1), (2022): e2021GC010158, https://doi.org/10.1029/2021GC010158.The Indus Fan, located in the Arabian Sea, contains the bulk of the sediment eroded from the Western Himalaya and Karakoram. Scientific drilling in the Laxmi Basin by the International Ocean Discovery Program recovered a discontinuous erosional record for the Indus River drainage dating back to at least 9.8 Ma, and with a single sample from 15.6 Ma. We dated detrital zircon grains by U-Pb geochronology to reconstruct how erosion patterns changed through time. Long-term increases in detrital zircon U-Pb components of 750–1,200 and 1,500–2,300 Ma record increasing preferential erosion of the Himalaya relative to the Karakoram between 8.3–7.0 and 5.9–5.7 Ma. The average contribution of Karakoram-derived sediment to the Indus Fan fell from 70% of the total at 8.3–7.0 Ma to 35% between 5.9 and 5.7 Ma. An increase in the contribution of 1,500–2,300 Ma zircons starting between 2.5 and 1.6 Ma indicates significant unroofing of the Inner Lesser Himalaya (ILH) by that time. The trend in zircon age spectra is consistent with bulk sediment Nd isotope data. The initial change in spatial erosion patterns at 7.0–5.9 Ma occurred during a time of drying climate in the foreland. The increase in ILH erosion postdated the onset of dry-wet glacial-interglacial cycles suggesting some role for climate control. However, erosion driven by rising topography in response to formation of the ILH thrust duplex, especially during the Pliocene, also played an important role, while the influence of the Nanga Parbat Massif to the total sediment flux was modest.This work was partially funded by a grant from the USSSP, as well as additional funding from the Charles T. McCord Chair in petroleum geology at LSU, and the Chevron (Gulf) Centennial professorship and the UTChron Laboratory at the University of Texas

Registros holocênicos de sedimentação mista carbonática-siliciclástica na plataforma continental externa do Rio Grande do Norte

The continental shelf of northeastern Brazil is characterized by a semiarid climate, warm temperatures, clear water, low sediment input, and mixed, carbonate-siliciclastic sedimentation. In this study, statistical analysis, mean grain size, sorting, skewness, and kurtosis were applied in 123 superficial sedimentary samples from the outer shelf of Rio Grande do Norte (RN) to verify the controlling factors of the distribution of sediments. In addition, geochemical analyzes were performed using the methods of X-ray diffraction (XRD) on 18 samples, X-ray fluorescence (FRX) on 20 samples, scanning electron microscopy, and energy dispersive spectroscopy on 10 samples (SEM/EDX), and 14C dating of six samples. Another technique used was digital image processing applied to Landsat 8/OLI satellite images in order to assess the spatial distribution of submerged features on the Brazilian continental shelf between the states of Amazonas and Bahia. The main results of this study showed that the statistical parameters, skewness, and kurtosis, were the ones that most evidenced the distinction between the siliciclastic and carbonate sediments of the outer shelf, indicating the terrigenous material as hydrodynamically incompatible with current conditions. The chemical compositions differed between the siliciclastic facies, composed of Si, Al, Fe, K, Zr, and Ti, and the bioclastic facies, constituted by the elements Ca, Sr and Mg. As for digital mapping, reefs occur in waters from 10 to 50 m deep, paleochannels showed a maximum extension of 35 km, occurring at depths of up to 80 m, and underwater dunes appear at depths from 10 to 100 m. Therefore, the integration of these data showed that carbonate sediments are from in situ and Holocene production, while siliciclastic sediments are relict and derived from continental rocks. The occurrence of reefs, paleovalleys and dunes indicate similar and favorable conditions for the establishment of these features during the Holocene along the Brazilian continental shelf.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA plataforma continental do nordeste brasileiro é caracterizada pelo clima semiárido, temperaturas quentes, águas claras, baixo aporte sedimentar e sedimentação mista, carbonática-siliciclástica. Neste estudo foram aplicadas análises estatísticas, tamanho médio do grão, selecionamento, assimetria e curtose, em 123 amostras sedimentares superficiais da plataforma externa do Rio Grande do Norte (RN) para verificar os fatores controladores da distribuição dos sedimentos. Além disso, análises geoquímicas foram realizadas através dos métodos de difração de raio X (DRX) em 18 amostras, fluorescência de raio X (FRX) em 20 amostras, microscopia eletrônica de varredura e espectroscopia por energia dispersiva em 10 amostras (MEV/EDX) e datação por radiocarbono com espectrometria de massa em 6 amostras. Outra técnica utilizada foi o processamento digital de imagens aplicado às imagens de satélite Landsat 8/OLI a fim de avaliar a distribuição espacial das feições submersas na plataforma continental brasileira entre os Estados de Amazonas e Bahia. Os principais resultados desse estudo demonstraram que os parâmetros estatísticos, assimetria e curtose, foram os que mais evidenciaram a distinção entre os sedimentos siliciclásticos e carbonáticos da plataforma externa, apontando o material terrígeno como hidrodinamicamente incompatível com as condições atuais. As composições químicas diferenciaram-se entre as fácies siliciclásticas, composta por Si, Al, Fe, K, Zr e Ti e as fácies bioclásticas, constituídas dos elementos Ca, Sr e Mg. Quanto ao mapeamento digital, os recifes ocorrem em águas de 10 a 50 m de profundidade, os paleocanais mostraram extensão máxima de 35 km, ocorrendo em profundidades de até 80 m, e as dunas subaquosas aparecem em profundidades de 10 a 100 m. Assim sendo, a integração desses dados, demonstrou que os sedimentos carbonáticos são oriundos da produção in situ e holocênicos, enquanto os siliciclásticos são relictos e derivados de rochas continentais. A ocorrência dos recifes, paleovales e dunas indicam condições semelhantes e favoráveis ao estabelecimento dessas feições durante o Holoceno ao longo da plataforma continental brasileira

Late Quaternary sedimentation off the Queensland continental margin (northeast Australia) in response to sea level fluctuations

Drilling during ODP Leg 133 offshore Cairns, northeast Queensland, provided a unique opportunity to document carbonate production and facies development on a mixed carbonate-siliciclastic margin. Recent studies have shown that variations in the sedimentology of Late Quaternary and Pliocene periplatform sediments (Schlager and James, 1978), deposited on continental slopes and in deep basins surrounding shallow carbonate platforms, are linked to changes in sea-level (Droxler et al., 1993; Schlager et al., 1994). However, considerable debate has arisen to the timing of the production and export of shallow water carbonate material, with respect to sea level change. Two main hypotheses have been proposed to explain the response of shallow water carbonate platforms to variation in Late Quaternary sea level: I) 'highstand shedding' and 2) 'lowstand shedding'. Proponents of highstand shedding argue that depositional systems shed most of its carbonate sediments onto the platform slopes during highstands of sea level. Conversely, during lowstands of sea level bank top production and export of carbonate material is restricted, and platform slopes are largely starved of bank derived carbonate (Schlager, 1992; Schlager et al., 1994 ). Supporters of lowstand shedding maintain that significant carbonate production and export of shallow water carbonate material occurs during lowstands (and highstands) of sea level (Bosellini, 1989; Goldhammer and Harris. 1989; Grammer and Ginsburg. 1992). In order to investigate the response of mixed carbonate-siliciclastic systems to variations in Late Quaternary sea level and climate change, core material was collected from Ocean Drilling Program (ODP) Leg 133, Sites 819 and 823 (northeast Australian margin). These two sites form part of an eastward extending transect of drill localities, offshore Cairns, Queensland, from the outershelf/upper-slope of the Great Barrier Reef (Sites 821 /820/819), into the Queensland Trough (Site 823) and ultimately onto the flanks of the Queensland Plateau (Sites 824 and 811 /825). Pelagic to hemipelagic sediments collected from these two sites were examined for the downcore distribution of grain size, magnetic susceptibility, carbonate content, variations in carbonate mineralogy (XRD), and major and minor element (XRF) geochemistry. Using high resolution foraminiferal stable oxygen isotopes, coupled with biostratigraphic and magnetostratigraphic datums, well defined age models for Hole 819A and Hole 823A have been constructed, although it was not an easy task as hiatuses occur in these records. Age models for the sequences recovered from Hole 819A and Hole 823A have been further refined using correlation with existing isotopic stratigraphies in the Pacific Ocean (ODP Hole 677, Raymo et al., 1989), and comparison with high resolution sedimentologic records from other ODP Leg 133 marine sequences. Analysis of the mineralogical, sedimentological and geochemical records from Holes 819A and 823A indicate that, over the last 1.1 million years, highstands of sea level (and during the early regression) are characterized by increased shallow water carbonate production, and deposition on the upper slope. This pattern of carbonate deposition is consistent with the highstand carbonate shedding scenario outlined by Schlager et al. (1992), and Schlager et al. ( 1994 ). Lowstands of sea level (and particularly the early transgression) are characterized by increased deposition of non-carbonate (mainly terrigenous) material and/or were not diluted by shallow water carbonate platform material. During the lowstands of sea level the shallow water carbonate factories were switched off. Therefore, the sediments deposited during lowstands of sea level tend to record the greater influence of pelagic driven carbonate. Although the above mentioned scenario of highstand shedding applies to the entire record of 1.1 million years. mineralogical and geochemical data indicate that shallow burial diagenesis, and dissolution of solution sensitive carbonate, occurred in the lower part of the records. The diagenesis and dissolution, however, have played only a minor role in determining the composition of the Queensland margin sediments. Variations in the terrigenous input (Cr/Al and Ti/AI ratios) in Queensland margin sediments indicate that interglacial periods were generally wetter than corresponding glacials or lowstands of sea level, during the Late Quaternary