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climate of the region is the result of the permanent equatorial low-pressure zone (tropical convergence). Changes in sea level are known to have occurred during the last 30,000 years.
Laterally extensive domed peat deposits are forming on the coastal plain and on offshore islands. These deposits form because organic matter is accumulating faster than it can decay. High rainfall and dissolved organic acids inhibit decay and cause leaching of mineral matter, leading to the low concentrations of ash (less than 3 percent) and sulfur (less than 0.5 percent) in the peat. Sand and clay are generally being removed from the vicinity of the peat swamps by tidal currents; sediments are being deposited only in a few places in the estuaries and in the Straits of Malacca. Most sediment is being transported northwest through the Straits to the Andaman Sea.
dized tracts of burrowing marine organisms, which have been eroded from the underlying silty clay. The oxidized burrows record three probable changes in sea level. First, during an earlier period of high sea level (approximately 30,000 years ago), burrowing marine organisms left tracks and trails in the silty clay bottom sediment. These burrows were mineralized with an iron carbonate mineral known as siderite. Approximately 18,000 years ago, during a lower stand of sea level, this bottom surface was exposed to the atmosphere, which oxidized the iron carbonate to iron oxide. Finally, about 5,000 years ago, sea level rose to its present position. Bottom currents are presently eroding and redepositing the burrows and shell fragments. These sealevel changes combined with the wet tropical climate of the region have
Figure 3. Land area of the continental shelf that was exposed approximately 18,000 years ago during a time of lower sea level.
Phase two was conducted in a coastal setting in West Kalimantan (fig. 2). This study covered an area of approximately 9,300 square miles bounded on the east by the estuary of the Sambas River and on the west by the open water of the South China Sea. This second area was chosen for study because sedimentation is occurring on an open shallow shelf, seaward of a significant peat deposit. Such environments appear to be common in the rock record, but the modern counterpart has not been studied extensively.
Sedimentation is controlled by tidal currents in the Sambas estuary and by tidal and longshore currents along the coast. Like the Sumatra estuaries, the Sambas is erosional except near the mouth where a mouth bar or tidal delta appears to be developing. In contrast to the coastline of Sumatra, the coast in the study area of West Kalimantan may be slowly building seaward, as the result of clay being deposited in the intertidal and near-shore environments and sand forming small beaches and tidal flats. The offshore area is similar to the area offshore of Sumatra; the bottom surface appears to be erosional and highly irregular. The seafloor is covered by a thin veneer of coarse-grained sand and gravel, composed of fragments of shells and the oxi
The joint USGS-DMR research team in a peat swamp in the coastal plain of central Sumatra. (Photograph by James C. Cobb, Kentucky Geological Survey.)
foreign-national scientists and technicians either individually in-country or collectively in groups at scheduled regional training sessions. Examples include the marine geology course in Chile (15 participants), the hazards course in Italy (20), the cartography course in Bangladesh (22), and the deformation monitoring volcano hazards evaluations in Colombia (30), Peru (6), and Guatemala (5). Eighteen countries benefited from these USGS overseas training efforts.
Activities with the countries listed below were conducted by the USGS in fiscal year 1988 under bilateral agreements sanctioned by the Departments of State and of the Interior: Argentina
Mapping with satellite imagery. Bangladesh
Strengthening the Geological Survey of
Evaluation of SPOT/Landsat images and map revision at 1:50,000 scale; mineral deposits modeling workshop on gold and
Marine geology; geophysics; ore-deposit models; water resources; platinum-group elements; Great Lakes seismicity; Arctic research; mapping data exchange; border
digital mapping; atmospheric deposition. Chile
Seismic zoning; improved earthquakeresistant designs; marine-geology training
Surveying and mapping-cartographic applications of remote sensing and development of geographic information systems. Earth sciences -pyrophyllite deposits; comparative geochemical anomalies in Xinjiang and southwestern United States; modeling for Bayan Obo iron-niobium-rare earth deposit in inner Mongolia; comparative geology of southern China and western U.S. Surface water-sediment transport; hydrologic equipment and measurements; hydrologic extremes; analytical techniques; cold-regions hydrology; hydrologic data exchange. Earthquakes - deep crustal structures in fault zones; premonitory phenomena; crustal stress; seismic networks; rock mechanics; intraplate active faults. Dominican Republic
Study of biochemical corrosion of gates of the Sabama Yequa Reservoir. El Salvador Geologic hazards assessment; evaluation of seismic hazards and compilation of seismic risk map.
Oceanography; geophysics; radioactive wastes; minerals assessment; borehole geophysics application to water resources; seaice monitoring; remote sensing in Polar
Marine seismology; radioactive wastes; petroleum resource assessment; Antarctic research; sea-ice monitoring; marine miner
als assessment. Hungary
Petroleum resource potential of the Pan
nonian Basin; geophysics. Iceland
Geophysics; geology; hydrology. India
Multidisciplinary workshops; identification
of mutually beneficial joint projects. Indonesia
Volcano monitoring; marine geology; peat swamps as coal field analogs. Italy
Installation of digital seismographs; earthquake reconstruction; training course on hydrological and landslide hazards; improvement of capability for early warn
ings of volcanic eruptions. Japan
Deeply buried mineral deposits; gold deposits; debris flows; sediment transport on con
tinental shelves and in estuaries. Jordan
Seismic network; remote sensing. Korea
Sedimentary basin analysis. Mexico
Border mapping cooperation; color image maps.
tries: Mauritania, Senegal, Gambia, Guinea-Bissau, Cape Verde, Mali, Niger, Burkina, and Chad. • Grasshopper and locust habitat identification and monitoring by remote sensing in Chad, Mali, Mauritania, Niger, and Sudan. • Antarctic research including acquisition of geodetic data, aerial photography, and satellite imagery to produce base maps and to assess changes in the glaciers and ice sheets composing the margin of Antarctica due to global change; operation of the Scientific Committee on Antarctic Research (SCAR) Library for Cartography and Geodesy; seismology and data telecommunications at the South Pole; ice cap motions, sea-ice monitoring, and low-frequency-radar ice experiments; lakes in dry valleys as related to the global carbon cycle. • Interagency Volcano Early Warning Disaster Assistance, which provides for emergency responses to crises related to volcanic eruptions. • Advisory consultations, particularly in resource assessment methodologies, to intergovernmental geoscience organizations in eastern Asia; preparation of regional base maps at 1:2,000,000 scale covering approximately 12 million square miles. • Mineral deposit evaluations for the Pacific Trust Territories; assessment work on Guam and Saipan. • Circum-Pacific Mapping Project, program coordination and the cartographic preparation of about 60 thematic maps. • Comparative earthquake and tsunami potential for zones in the Circum-Pacific. • Southwestern Pacific offshore exploration for petroleum resources.
For the first time since 1933, the United States played host to the International Geological Congress. The National Academy of Sciences and the USGS were the official hosts for the 28th session of the Congress, held in Washington, D.C., July 9–19, 1989.
The goal of the Congress is to encourage the advancement of fundamental and applied research in the earth sciences worldwide. To achieve this goal, an international congress is organized about every 4 years by scientists in member countries of the International Union of Geological Sciences. The Congress brings together a broad representation of the world's earth scientists for a unique opportunity to exchange scientific information and concepts.
The Congress provides a special forum for new and sustained international exchange of geological knowledge. It is an event with long-term value in the continuing effort to advance worldwide understanding of the Earth and thereby improve our capability to manage its resources wisely.