Strong Forcing The rapid uplift of New Guinea has created elevations on the island that locally exceed 4000 m, and combined with the wet-tropical setting result in annual sediment yields exceeding 1000 t/km2. Large episodic sediment delivery to river channels occurs due to landsliding induced by intense rain and earthquakes, and submarine mass-wasting likely plays a major role in sediment redistribution on the continental slope. The total sediment discharge from rivers draining New Guinea is estimated to be about 1.5 times that of the Amazon River, although the island has only one-eighth the drainage area. A collision margin to the north, and a foreland basin to the south present a range of tectonic end members. High carbonate production is present around the island along with both modern and ancient carbonate-siliciclastc transitions.
Active Sedimentation From Source to Sink - The combination of high sediment yield and collision margins that mimic low-stand conditions provides ample opportunities to examine active processes from mountain top to abyssal plain. Each of the major river systems has gravel bedded headwater streams that feed sand-bedded rivers with extensive floodplains. Ideal conditions exist to quantify how upland sediment pulses are attenuated through exchange with lowland sediment storage systems. The floodplain systems are extensive enough to generate a wide range of depositional environments but small enough to be manageable for field studies. Along the northern New Guinea coast, tectonic activity has produced subsiding coastal basins, such as that along the lower Sepik, allowing investigation of the role such trapping plays in margin development. Shelves are narrow or absent off the north coast, where rivers discharge directly into submarine canyons and active slope-basin processes can be quantified. Along the southern coast in the Gulf of Papua, the shelf is wider and sediment storage in mangroves and on the shelf is important although some sediment enters Pandora Trough (a submarine canyon in the eastern Gulf of Papua). Active coral reefs extend into the Gulf of Papua from northern Australia and provide ample opportunities to examine this major carbonate-clastic transition zone. In addition, recent and historical volcanism on the north coast of PNG provides excellent datable, correlative surfaces that give insight into marine sedimentary processes. The marine record, in turn, will allow assessment of historical volcanic activity in the region.
Closed System The moderate-sized drainage basins and the presence of coastal basins in the north, and a broad shelf with mangroves in the south, should allow sediment budgets in these areas to be fairly well constrained. More problematic will be the lower portions of some of the dispersal systems, where deposits from a large number of small mountainous rivers likely coalesce. "Line-source" input of sediment is an important aspect of mountainous coastal systems that should attract further investigation.
High-Resolution Record High accumulation rates resulting from high inputs, along with tectonic-induced subsidence in many areas combine to offer excellent temporal resolution in the preserved sedimentary record around New Guinea. In the marine environment, high rates of siliciclastic accumulation inhibit benthic habitation and bioturbation, which, in other marine environments, tends to blur stratagraphic resolution. In addition, frontal storms are very rare or non-existent in PNG due to its close proximity to the equator. Sedimentary features formed from the catastrophic erosion and redeposition of such storms can dominate the stratigraphic record at higher latitudes. The greater temporal resolution within accumulated strata means that the history of environmental events (both natural and anthropogenic) should be well preserved in continental-margin deposits around New Guinea.
Presence of Carbonate Environments The worlds most extensive and productive barrier reef (i.e., The Great Barrier Reef) grades into patch reefs extending into the Gulf of Papua. Here, and throughout the waters separating New Guinea and Australia (e.g., Arafura Sea, Gulf of Carpenteria), carbonates interfinger with siliciclastic deposits providing an unparalleled opportunity to examine interactions between these contrasting environments through time. Fringing reefs, some of which have been extensively studied for their record of sea level (i.e., The Huon Peninsula), exist in abundance along the north coast. The carbonate deposits in these areas provide geochronological constraints, sea-level and other information which will be invaluable in understanding intercalated siliciclastic deposits.
Background Data and Infrastructure A number of past and ongoing studies around the island of New Guinea (see "Example Sites") provide ample background to plan focused experiments within the context of MARGINS. For example, the recently completed COASTPLAN project (executed by PNG Geological Survey and the Commission for Coastal and Offshore Geoscience in East and Southeast Asia, and funded by the Government of the Netherlands) focussed on the lower Markham valley, and neighbouring Butibum and Busu rivers assessing the geology and natural hazards of Lae city and surroundings. The project synthesized all existing information for the region, and gathered new data by processing comparative satellite imagery, and offshore surveying in the Huon Gulf. River discharge records are variably known in New Guinea, for example they are well documented for the Fly, but poorly documented for the Sepik. The Fly River may be one of the better studied and actively gauged large rivers in the world (see Fly River). Considerable topographic and remote sensing data have been generated for PNG associated with mining and oil exploration. It is likely that these industries will be willing to share their digital data. There are Landsat 5 and 7 images available (see "Example Sites") and the 1: 100,000 topographic maps have been digitized. Digital 20-m contour data may be available for the Sepik and the headwaters of the Ok Tedi Fly system. Lengthy time-series data of ocean conditions (e.g., waves and currents) is unavailable but shorter length studies have been conducted in the GOP. Aerial photography is available for the entire country as well as topographic sheets and geologic maps (see PNG National Mapping Bureau website http://www.datec.com.pg/nmb/default.html.
Logistics The PNG government is progressive with regard to the issuance of research visas and permissions for foreign vessels to work in coastal waters. Transportation and conditions for land-based work will be more difficult in some cases as a result of limited transportation network. Coordination with ongoing Australian research efforts in PNG will be required. Australian scientists in a range of federal labs (e.g., Australian Institute of Marine Science, Commonwealth Scientific and Industrial Research Organization) and universities (e.g., James Cook University, Australian National University, University of Melbourne) would be cooperative participants in the scientific efforts. Scientists from PNG (University of PNG, Department of Environmental Conservation, and Institute of National Studies) will participate in the project, and through existing Memorandums Of Understanding can guarantee clearances for US ships. Mining companies operating in the Fly catchment make extensive use of helicopters and ships. These companies, particularly Ok Tedi Mining Limited (OTML) have been able to provide crucial logistic support for environmental studies. Joe Buleka, Geological Survey Division, Department of Mineral Resources, Papua New Guinea has indicated his support for the Margins project, which can build on recent progress in understanding of the active geological processes in the lower Markham valley, the Lae area, and the inner Huon Gulf resulting from the recently completed CCOP COASTPLAN project.Studies in Irian Jaya (western Island) will require cooperation with the Indonesian government, which currently sponsors a number of marine and terrestrial studies.
Anthropogenic Influence New Guinea dispersal systems range from pristine (Sepik, Markham) to moderately impacted by human activity (Fly). Alterations to the Fly system by mining activities present a unique natural laboratory. From the perspective of the MARGINS program, the large influx of sediment in the Fly offers a unique opportunity to examine a large sediment signal, with a distinctive chemical composition, that can be exploited to document and model sediment transfer processes through the entire system. The influx of sediment has not fundamentally changed the transport processes. It is, however, a strong, long-duration signal that differs from short term stochastic introduction associated with natural loading events. The extensive data already collected and the established precipitation and hydrologic program in the Fly greatly increases the opportunity and possibility of obtaining accurate sediment budgets through the system.
Societal Relevance Major earthquakes and volcanic eruptions are relatively common in Papua New Guinea. More than 50 magnitude 7 or greater events have been experienced in the New Guinea vicinity since 1973 according to the USGS database (http://earthquake.usgs.gov/neis/epic/epic.html). Recent volcanism includes Rabaul, New Britain http://volcanoes.usgs.gov/Volcanoes/Rabaul/VAG.html and Manem Island. Eruption of the Rabual Volcano in 1937 killed more than 500 people. The frequency of tsunamis in New Guinea is not known, however the tectonic setting, especially along the north collision margin, suggests they may be fairly common. On Friday, 17 July 1998, a 15-m tsunami devastated villages located on barrier spits fronting Sissano lagoon. Over 2,000 lives were lost. Previous events are known to have occurred there. Historical tsunami deposits are hypothesized to be recorded in margin deposits along and offshore of the northern PNG coast. Their study could reveal more about the distribution and potential recurrence of these devastating events. Better understanding of the geological processes involved in sediment transport from the Markham and Busus rivers, the temporary sediment storage in coastal alluvial fans and fan deltas, and the subsequent sediment movement by sea floor processes in the inner Huon Gulf will be critical to future development of the city of Lae, PNG's most important port. These sedimentary processes provide hazards to coastal development and are engineering design constraints for future expansion of port facilities, (e.g. Buleka et al., 1999).
Leveraging Resources for Research Ongoing research efforts, particularly those led by Australian colleagues, should offer the potential for much synergism. For example, coordination with the Australian TROPICS program should be mutually beneficial. The potential for sharing ship time, laboratory resources, and obtaining logistical assistance from Australian colleagues would be an important consideration for a potential New Guinea study. The PNG government (Geological Survey) has expressed a desire to provide logistical help for completion of a MARGINS program in New Guinea.