Warta Geologi, Vol. 52, No. 1, April 2026, pp. 20-28
Yi Ning Fong*, Dominique Dodge-Wan, Prasanna Mohan Viswanathan
Department of Applied Sciences, Faculty of Engineering and Science, Curtin University Malaysia,
CDT 250, 98009 Miri, Sarawak, Malaysia
*Corresponding author email address: yining.fong@postgrad.curtin.edu.my
Abstract: Amber fragments recovered in situ from the Tukau Formation (Middle Miocene to Pliocene) in northwest Sarawak were analysed to assess their physical and chemical characteristics. Amber samples were collected from ten different localities and underwent diagnostic tests to evaluate hardness, solvent solubility, buoyancy, UV fluorescence, and burning reaction. The samples display melting points above 160 °C, hardness between 3-4 on the Mohs scale, non-reactivity to acetone, and a characteristic resinous odour upon heating, properties consistent with fossil amber. Fourier Transform Infrared (FTIR) spectra reveal consistent absorption bands at approximately 2920, 2863, 1694, 1454, 1374, 1042, and 887 cm-1, and display absorption patterns comparable to fossil dipterocarp (Class II) resins and distinct from succinite. When considered together with the diagnostic physical properties and the Neogene age of the host sediments, these observations support classification of the material as fossil amber rather than weakly polymerised resin. The spectral profile closely corresponds to that of resins from Dipterocarpaceae trees, suggesting a tropical lowland forest origin. The preservation of amber within fluvio-deltaic to shallow marine deposits indicates burial under conditions favourable for the preservation of organic matter. Tukau amber is thus comparable to Neogene dipterocarp-derived amber elsewhere in Borneo, providing insights into Miocene palaeoenvironments and vegetation in the region.
Keywords: Borneo amber, Tukau Formation, palaeoenvironment, Miocene, Dipterocarpaceae
References:
Abduriyim, A., Kimura, H., Yokoyama, Y., Nakazono, H., Wakatsuki, M., Shimizu, T., Tansho, M. & Ohki, S., 2009. Characterization of “green amber” with infrared and nuclear magnetic resonance spectroscopy. Gems & Gemology, 45, 158-177.
Álvarez-Parra, S., Bueno-Cebollada, C.A., Barrón, E., Pérez- Cano, J., Paredes-Aliaga, M.V., Rubio, C., Rodrigo, A., Meléndez, N., Delclòs, X. & Peñalver, E., 2024. Taphonomy and palaeoenvironmental interpretation of a new amber-bearing outcrop from the mid-Cretaceous of the Maestrazgo Basin (E Iberian Peninsula). Spanish Journal of Palaeontology, 39, 32.
Anderson, K.B., 1994. The nature and fate of natural resins in the geosphere—IV. Middle and Upper Cretaceous amber from the Taimyr Peninsula, Siberia—evidence for a new form of polylabdanoid of resinite and revision of the classification of Class I resinites. Organic Geochemistry, 21, 209-212.
Ashton, P.S., 2003. Dipterocarpaceae. In: Kubitzki, K., & Bayer, C. (Eds.), The Families and Genera of Vascular Plants, vol 5, Flowering Plants Dicotyledons. Springer, Berlin, Heidelberg. ISBN: 978-3-642-05714-4.
Banda, R.M. & Honza, E., 1997. Miocene stratigraphy of Northwest Borneo Basin. Bulletin of the Geological Society of Malaysia, 40, 1-11.
Bisulca, C., Nascimbene, P. C., Elkin, L. & Grimaldi, D.A., 2012. Variation in the deterioration of fossil resins and implications for the conservation of fossils in amber. American Museum Novitates, Number 3734. 9 p. https://doi.org/10.1206/3734.2.
Brasier, M., Cotton, L. & Yenney, I., 2009. First report of amber with spider webs and microbial inclusions from the earliest Cretaceous (c. 140 Ma) of Hastings, Sussex. Journal of the Geological Society, 166, 989-997.
Bray, P.S. & Anderson, K.B., 2009. Identification of Carboniferous (320 million years old) Class Ic amber. Science, 326, 132-134.
Brearley, F.Q., Banin, L.F., & Saner, P., 2017. The ecology of the Asian dipterocarps. Plant Ecology & Diversity, 9(5-6), 429-436.
Brody, R.H., Edwards, H.G.M. & Pollard, A.M., 2001. A study of amber and copal samples using FT-Raman spectroscopy. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 57, 1325-1338.
Collins, D.S., Johnson, H.D., Allison, P.A. & Damit, A.R., 2018. Mixed process, humid-tropical, shoreline–shelf deposition and preservation: Middle Miocene–Modern Baram Delta Province, Northwest Borneo. Journal of Sedimentary Research, 88, 399-430.
Collins, D.S., Johnson, H.D., Allison, P.A., Guilpain, P. & Damit, A.R., 2017. Coupled ‘storm‐flood’ depositional model: Application to the Miocene–Modern Baram Delta Province, Northwest Borneo. Sedimentology, 64, 1203-1235.
Collins, D. S., Johnson, H.D. & Baldwin, C.T., 2020. Architecture and preservation in the fluvial to marine transition zone of a mixed-process humid-tropical delta: Middle Miocene Lambir Formation, Baram Delta Province, north-west Borneo. Sedimentology, 67, 1-46.
Dutta, S., Mallick, M., Bertram, N., Greenwood, P.F. & Mathews, R.P., 2009. Terpenoid composition and class of Tertiary resins from India. International Journal of Coal Geology, 80, 44-50.
Fong, Y.N., Dodge-Wan, D. & Prasanna, M.V., 2024. Observations on palynology of the Tukau Formation in northwest Sarawak, Malaysia. Bulletin of the Geological Society of Malaysia, 78, 75-90.
Garcia-Valles, M., Di Mariano, A., Alfonso, P., Noguès, J. & Martínez, S., 2023. Differentiation between copal and amber by their structure and thermal behaviour. Journal of Thermal Analysis and Calorimetry, 148, 13027-13037.
Ghazoul, J., 2016. Dipterocarp biology, ecology, and conservation. Oxford University Press, Oxford, UK. 320 p. ISBN: 9780199639656.
Grimaldi, D.A., Shedrinsky, A., Ross, A. & Baer, N.S., 1994. Forgeries of fossils in “amber”: History, identification and case studies. Curator: The Museum Journal, 37, 251-274.
Hutchison, C.S., 2005. Geology of North-West Borneo, Elsevier, Amsterdam. 444 p. ISBN: 0080460895, 9780080460895.
Jong, J. & Kessler, F.-L., 2019. The Setap Shale Formation on either side of the Baram Line Divide: Facies aspects and tectonic implications. Bulletin of the Geological Society of Malaysia, 67, 53-65. https://doi.org/10.7186/bgsm67201907.
Karolina, D., Maja, M.-S., Magdalena, D.-S. & Grażyna, Ż., 2022. Identification of treated Baltic amber by FTIR and FT-Raman – A feasibility study. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 279, 121404.
Kessler, F.-L., 2023. The sea level rose fast, but Sarawak was rising faster. Warta Geologi, 49, 8-13.
Kessler, F.-L. & Jong, J., 2014. Habitat and C-14 ages of lignitic terrace deposits along the northern Sarawak Coastline. Bulletin of the Geological Society of Malaysia, 60, 27-34.
Kessler, F.-L. & Jong, J., 2015. Northwest Sarawak: A complete geologic profile from the Lower Miocene to the Pliocene covering the Upper Setap Shale, Lambir and Tukau Formations. Warta Geologi, 41, 45-51.
Kessler, F.-L. & Jong, J., 2016. Shape parameters of clay and quartz clasts in the Neogene Tukau and Lambir Formations, NW Sarawak. Warta Geologi, 42, 63-68.
Kessler, F.-L. & Jong, J., 2017. The roles and implications of several prominent unconformities in Neogene sediments of the greater Miri area, NW Sarawak. Warta Geologi, 43, 1-8.
Kessler, F.-L., Jong, J. & Nagarajan, R., 2023. Synopsis of Upper Tukau Deposits along the Sungai Rait Road, Miri District, Sarawak, Malaysia. Bulletin of the Geological Society of Malaysia, 75, 73-84.
Kessler, F.-L. & Padmanabhan, E., 2008. Aquifer and ferric spring deposits south of Miri, Sarawak: Impact on facies characterisation of coastal sediments. Warta Geologi, 34, 243-246.
Kocsis, L., Usman, A., Jourdan, A.-L., Hassan, S.H., Jumat, N., Daud, D., Briguglio, A., Slik, F., Rinyu, L. & Futó, I., 2020. The Bruneian record of “Borneo Amber”: A regional review of fossil tree resins in the Indo-Australian Archipelago. Earth-Science Reviews, 201, 1-21.
Labandeira, C.C., 2014. Amber. The Paleontological Society Papers, 20, 163-216.
Lambert, J.B., Tsai, C.Y.-H., Shah, M.C., Hurtley, A.E. & Santiago- Blay, J.A., 2012. Distinguishing amber and copal classes by proton magnetic resonance spectroscopy. Archaeometry, 54, 332-348.
Langenheim, J.H., 2003. Plant resins: Chemistry, evolution, ecology, and ethnobotany. Timber Press, Portland, Cambridge. 586 p. https://doi.org/10.1093/aob/mch103.
Lewis, D.W. & McConchie, D., 2012. Analytical sedimentology. Springer, Dordrecht. 197 p. ISBN 1461526361, 9781461526360.
Li, X., Wang, Y., Shi, G., Lu, R. & Li, Y., 2023. Evaluation of natural ageing responses on Burmese amber durability by FTIR spectroscopy with PLSR and ANN models. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 285, 121936.
Liechti, P., Roe, F. W., Haile, N.S. & Kirk, H.J.C., 1960. The geology of Sarawak, Brunei and the Western part of North Borneo. US Government Printing Office, Kuching. 360 p.
Madon, M.B.H., 1999. Geological setting of Sarawak. In: Leong, K.M. (Ed.), The Petroleum Geology and Resources of Malaysia. Petronas, Kuala Lumpur. 665 p. ISBN 983- 9738-10-0.
Martı́nez-Delclòs, X., Briggs, D.E.G. & Peñalver, E., 2004. Taphonomy of insects in carbonates and amber. Palaeogeography, Palaeoclimatology, Palaeoecology, 203, 19-64.
Maury-Lechon, G., & Curtet, L., 1998. Biogeography and Evolutionary Systematics of Dipterocarpaceae. In: Appanah, S., Turnbull, J.M. (Eds.), A Review of Dipterocarps: Taxonomy, Ecology, and Silviculture. CIFOR, Jakarta, Indonesia. ISBN 979-8764-20-X.
Montoro, Ó.R., Lobato, Á., Baonza, V.G. & Taravillo, M., 2018. Infrared spectroscopic study of the formation of fossil resin analogs with temperature using trans-communic acid as precursor. Microchemical Journal, 141, 294-300.
Manuscript received 26 November 2025;
Received in revised form 6 January 2026;
Accepted 11 February 2026
Available online 30 April 2026
DOI: https://doi.org/10.7186/wg521202603
0126-5539; 2682-7549 / Published by the Geological Society of Malaysia.
© 2026 by the Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC-BY) License 4.0
