Metal concentrations in sediments from tourist beaches of Miri City,Sarawak, Malaysia (Borneo Island)

Forty-three sediment samples were collected from the beaches of Miri City, Sarawak, Malaysia to identify the enrichment of partially leached trace metals (PLTMs) from six different tourist beaches. The samples were analyzed for PLTMs Fe, Mn, Cr, Co, Cu, Ni, Pb, Sr and Zn. The concentration pattern suggest that the southern side of the study area is enriched with Fe (1821–6097 μg g⁻¹), Mn (11.57–90.22 μg g⁻¹), Cr (51.50–311 μg g⁻¹), Ni (18–51 μg g⁻¹), Pb (8.81–84.05 μg g⁻¹), Sr (25.95–140.49 μg g⁻¹) and Zn (12.46–35.04 μg g⁻¹). Compared to the eco-toxicological values, Cr > Effects range low (ERL), Lowest effect level (LEL), Severe effect level (SEL); Cu > Unpolluted sediments, ERL, LEL; Pb > Unpolluted sediments and Ni > ERL and LEL. Comparative results with other regions indicate that Co, Cr, Cu, Ni and Zn are higher, indicating an external input rather than natural process.     

SPATIO-TEMPORAL ASPECTS OF LAND USE AND LAND COVER CHANGES IN THE NIAH CATCHMENT, SARAWAK, MALAYSIA

This paper focuses on the large‐scale land use and land cover changes that have taken place in Sarawak state, East Malaysia over the three decades of 1972‐2002. Results are presented from a detailed land use and cover change (LUCC) study in the Niah River catchment using satellite imagery, questionnaire surveys and interviews. Successive waves of land cover changes have taken place. Large forest areas have been logged and gradually replaced by oil palm plantations, which now occupy more than 40 per cent of the total land area in the catchment. Concurrently, small‐scale farming systems have also changed. Formerly dominant Iban shifting cultivation practices are increasingly being replaced by cash crop production on permanent fields and impacted by off‐farm activities involving many ethnic groups. It is argued that land cover changes are continuous and complex processes involving a large number of variables which can be analysed for different time periods at various scales.     

Nature and significance of the West Baram and Tinjar Lines,NW Borneo

A key consideration in tectonic models for SE Asia and opening of the South China Sea is the role that the West Baram and Tinjar Lines of NW Borneo may have played in accommodating the motion of crustal blocks displaced from Asia following India's collision. There are few studies that focus on these “lines”. Using onshore geological studies and offshore seismic data to address the origin and tectonic significance of these, this paper concludes that rather than a major transform boundary between Luconia and the Dangerous Grounds, the West Baram Line marks the boundary between domains of continental crust that underwent differential extension in the Eocene. The Baram Basin is underlain by hyperextended continental crust on the NE side of the Baram Line. The strong contrast in the geological features across the Tinjar and West Baram Lines likely reflects ancient differences in crustal rheology with Luconia being the more rigid block. Although lack of significant strike slip faulting along the West Baram Line poses problems for tectonic models in which a wide proto-South China Sea is subducted beneath NW Borneo, intra-plate deformation, such as partial inversion of the Dangerous Grounds rift, offers a potential mechanism to mass balance blocks displaced from Asia with the reduced strike slip motion along the West Baram Line.     

沙捞越盆地东部构造的差异性及其对沉积的控制作用

从沙捞越盆地形成构造演化入手,分析了造成盆地东部北卢卡尼亚、中卢卡尼亚和巴林基安3个次盆构造差异性的原因,讨论了这种构造的差异性对盆地内沉积的控制作用。认为:婆罗洲逆时针旋转影响下卢卡尼亚陆块向婆罗洲的俯冲碰撞是导致盆地东部各次盆构造差异性的主要原因;受古地貌的影响,中中新世-晚中新世,中卢卡尼亚次盆以发育碳酸盐岩沉积为特征,而北卢卡尼亚和巴林基安2个次盆则主要为海相碎屑岩沉积;中中新世,中卢卡尼亚次盆稳定构造背景为盆地内碳酸盐岩建隆的生长创造了有利条件;中卢卡尼亚次盆内发育的早期断层控制了碳酸盐岩建隆的类型及其分布。     

Carbonate platforms in wedge-top basins: An example from the Gunung Mulu National Park,Northern Sarawak (Malaysia)

The Melinau carbonate platform initiated during the Mid-Eocene on a rotating slice of the Rajang accretionary prism. The differential sedimentary loading enhanced a rotation of the mobile substratum and created an elongated, asymmetrical wedge-top basin. The extensional southern margin of the basin consists of a 2100–2200-m-thick section of Eocene-to-Oligocene carbonates. These thin laterally towards the northern margin of the basin, where a carbonate factory was active on a postulated underlying thrust. Backstepping and dismemberment of the carbonate system started during the latest Oligocene and deep-marine sedimentation became prevalent over the entire region during the Early Miocene.