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Modern stable isotopic ( δ 18 O, δ 2 H, δ 13 C) variation in terrestrial, fluvial, estuarine and marine waters from north‐central Sarawak, Malaysian Borneo
Author(s) -
Stephens Mark,
Rose James
Publication year - 2005
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.1218
Subject(s) - tributary , stalagmite , geology , δ18o , fluvial , stable isotope ratio , estuary , drainage basin , hydrology (agriculture) , context (archaeology) , cave , water cycle , structural basin , oceanography , paleontology , ecology , geography , holocene , cartography , geotechnical engineering , biology , physics , quantum mechanics
Stable isotope data on humid tropical hydrology are scarce and, at present, no such data exist for Borneo. Delta 18 O, δ 2 H and δ 13 C were analysed on 22 water samples from different parts of the Sungai (river) Niah basin (rain, cave drip, rainforest pool, tributary stream, river, estuary, sea) in north‐central Sarawak, Malaysian Borneo. This was done to improve understanding of the modern stable isotope systematics of the Sungai Niah basin, essential for the palaeoenvironmental interpretation of the Late Quaternary stable isotope proxies preserved in the Great Cave of Niah. The Niah hydrology data are put into a regional context using the meteoric water line for Southeast Asia, as derived from International Atomic Energy Agency/World Meteorological Organization isotopes in precipitation network data. Although the Niah hydrological data‐set is relatively small, spatial isotopic variability was found for the different subenvironments of the Sungai Niah basin. A progressive enrichment occurs towards the South China Sea ( δ 18 O −4·6‰; δ 2 H −29·3‰; δ 13 C −4·8‰) from the tributary stream ( δ 18 O −8·4‰; δ 2 H −54·7‰; δ 13 C −14·5‰) to up‐river ( δ 18 O c. −8‰; δ 2 H c. −51‰; δ 13 C c. −12‰) and down‐river values ( δ 18 O c. −7·5‰; δ 2 H c. −45‰; δ 13 C c. −11‰). This is thought to reflect differential evaporation and mixing of different components of the water cycle and a combination of depleted biogenic δ 13 C (plant respiration and decay) with enriched δ 13 C values (due to photosynthesis, atmospheric exchange, mixing with limestone and marine waters) downstream. Cave drip waters are relatively enriched in δ 13 C as compared to the surface waters. This may indicate rapid degassing of the cave drips as they enter the cave atmosphere. Copyright © 2005 John Wiley & Sons, Ltd.