Geomorphology of the Lower Mary River Plains Northern Territory

The Mary River is one of several large seasonal rivers which drain northwards into van Diemen Gulf in the Northern Territory. It has a catchment area of about 7700 square km. Most of its drainage is across a dissected, lateritised land surface, termed the Koolpinyah land surface, but near the coast it flows through extensive horizontal plains, covering about 1100 square km which are the subject of this study

The Soils of Kiritimati (Christmas) Island, Kiribati, Central Pacific: New Information and Comparison with Previous Studies.

v. ill. 23 cm.QuarterlyKiritimati, the largest land area atoll in the world, is undergoing rapid population increase, and, given the isolation of the island, local food production will have to be expanded to support the residents. Two soils investigations were completed in the 1960s, but no additional information on the soil resources of the island has been produced since that time. In this study, 15 soil profiles were described and analyzed. Where possible, comparison has been made with previous work, and discussion of the soil-forming factors is presented. Results confirm that soils are weakly developed (Entisols) with relatively low organic matter contents and low water-retention capacity. These properties are expected from the age of the parent materials and the relatively dry climate of the island. Total elemental analyses show that the soils contain very low concentrations of potassium and important trace elements (iron, manganese, copper, and zinc), which will limit any plant production. Classification of the soils identified eight soil families, mainly separated on the basis of content of larger coarse fragments and soil moisture regime, including the influence of groundwater. Comparison with previous studies showed that although different nomenclature and classification systems were used, similar soil patterns were observed, and the soils of Kiritimati are relatively unique in the Pacific islands

Coral microatolls and their role as fixed biological indicators of Holocene sea-level changes

Corals microatolls are individual colonies of massive coral that have grown up to a level at which further upward growth is constrained by exposure at low tide, and which then continue to grow outwards, resulting in a flat-topped discoid morphology. Typically, microatolls comprise a single colony of massive Porites up to several metres in diameter. Modern microatolls are living on their outer margin but are predominantly dead on their upper surface. Microatolls are fixed biological sea-level indicators of the former upper limits to coral growth providing information on sea level at several temporal scales. Fossil microatolls have been used extensively to reconstruct broad patterns of Holocene sea-level trends in the Indo-Pacific reef province. Where they are preserved at a height above that of their living counterparts in the eastern Indian Ocean, Southeast Asia, northern Australia, and across much of the equatorial Pacific Ocean, they indicate that reef flats have experienced relatively higher sea levels in the mid- and late Holocene. Progressively lower corals have been interpreted to record the fall in sea level to its present position over millennial time scales. Large specimens of microatolls can reach several metres in diameter and contain a growth record of tens to hundreds of years; the upper surfaces of these can be used to track the pattern of sea-level variation over several decades. In this paper we explore the potential for using concentric annuli and subtle undulations preserved on microatoll upper surfaces to interpret sea-level changes over decadal to millennial time scales. We demonstrate that in the central Pacific modern microatolls preserve a surface morphology that reflects oscillations of sea level associated with El Niño. We evaluate the extent to which similar fluctuations may be recorded in the morphology of Indian Ocean microatolls, and the circumstances which promote the preservation of these morphological records of sea-level change over longer time scales. We discuss the potential to reconstruct extended records of sea-level change by using geochemical signatures preserved within microatoll skeletons to improve cross-correlations between colonies, and assess the precision with which sea level can be inferred

Landscape variability and the response of Asian megadeltas to environmental change

Deltas, occurring at the mouths of river systems that deposit sediments as they enter the sea, are some of the most dynamic sedimentary environments. They contain a long, and often economically significant, sedimentary record of their response to past episodes of climate and sea-level change. Geological investigation of these deposits, and the processes controlling sedimentation, provide insights into the response of deltas to environmental change, which in turn may offer rational and cost-effective strategies for the sustainable management of natural resources and land use in these dynamic systems in the face of future environmental change

Holocene reef growth in Torres Strait

The platform and fringing reefs of Torres Strait are morphologically similar to reefs of the northern Great Barrier Reef to the south, except that several are elongated in the direction of the strong tidal currents between the Coral Sea and the Gulf of Carpentaria. Surface and subsurface investigations and radiocarbon dating on Yam, Warraber and Hammond Islands reveal that the initiation and mode of Holocene reef growth reflect antecedent topography and sea-level history. On the granitic Yam Island, fringing reefs have established in some places over a Pleistocene limestone at about 6 m depth around 7000 years BP. Emergent Holocene microatolls of Porites sp. indicate that the reefs have prograded seawards while sea level has fallen gradually from at least 0.8 m above present about 5800 years BP. On the Warraber Island reef platform drilling near the centre indicated a Pleistocene limestone foundation at a depth of about 6 m over which reefs established around 6700 years BP. Reef growth lagged behind that on Yam Island. Microatolls on the mature reef flat indicate that the reef reached sea level around 5300 years BP when the sea was around 0.8–1.0 m above present. On the reef flat on the western side of Hammond Island bedrock was encountered at 7–8 m depth, overlain by terrigenous mud. A progradational reef sequence of only 1–2 m thickness has built seaward over these muds, as sea level has fallen over the past 5800 years. Reef-flat progradation on these reefs is interpreted to have occurred by a series of stepwise buildouts marked by lines of microatolls parallel to the reef crest, marking individual coalescing coral heads. Detrital infill has occurred between these. This pattern of reef progradation is consistent with the radiocarbon dating results from these reefs, and with seismic investigations on the Torres Reefs