What is it about?
The Sarawak state in East Malaysia has a coast of 1035 km. This study focuses on the stretch of 74 km between Kuala Baram and Kuala Sibuti to explore the distribution of major, trace and rare earth elements (REE).
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Why is it important?
The river sediments accumulate over the beaches for an extended period. Thus, they provide an overall assessment of long-term geological processes which can resolve long-standing questions on tectonics and geochemical evolution. Here we report such information which has answered two critical questions: 1) What is the source of the sediments - felsic or mafic? 2) From where these sediments were derived - active or passive margin. Moreover, this work exposes the shoreline processes and their impact on the geochemical evolution of the sands. Here we report how the prevailing hydrological regime divided the study area into two segments and show how the geochemical composition is accordingly affected. Thus, the weathering and mobility of the elements are reported for two sections of the study area. These two parts are differentiated by their grain size distribution due to the prevailing hydrological regime. The mobility of Na is high in the SW part (towards Sibuti) while Ca leads the weathering series in the NE part (towards Baram). The sands exhibit a weathering trend from granodiorite to shale. The sands show signs of sorting and recycling with a passive margin source of quartzose (quartz arenite) sediments dominated by felsic source. The REE are predominantly in the sand fraction in the NE segment while fractionation of HREE from LREE is observed in the SW part. Risk indices points to the enrichment of Cu and Zn. This study provides the first-ever comprehensive geochemical database of the beach sands from Miri to Sibuti. Similar work extended to the entire coastal region of Sarawak may reveal the geochemical and tectonic processes that are important in the geological evolution of this region.
Perspectives
A significant finding is that the prevailing hydrological regime controls the geochemical composition of the elements and divides the area into two [North East (NE) and (SW)] segments. At the boundary of these two segments, the Baram and Mri rivers debouch their sediments. The Sarawak state has two major river systems - the Rajang and Baram and several other streams. Thus, the coastal processes may be different in different segments. By bringing out a comprehensive geochemical database of the entire coastal region, critical information essential for the reconstruction of the geological history of this region can be obtained. Such a piece of information shall be able to complement the extensive hard work carried out inside the jungle for the exploration of the geology.
Dr. ESWARAMOORTHI SELLAPPA GOUNDER
GeoScientifix
Read the Original
This page is a summary of: Geochemical Characterization of Beach Sediments of Miri, NW Borneo, SE Asia: Implications on Provenance, Weathering Intensity, and Assessment of Coastal Environmental Status, January 2019, Elsevier,
DOI: 10.1016/b978-0-12-814350-6.00012-4.
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