~ l Pergamon PII: S1040--6182(96)00011-0 Quaternary International, Vol. 37, pp. 81-87,1997. Copyright © 1996 INQUA/Elsevier Science Ltd Printed in Great Britain. All rights reserved. 104(0-6182/97 $32.00 RECENT CLIMATE VARIATION SIGNALS FROM CORALS IN TIMOR, INDONESIA W.S. Hantoro,* N. Nganro,~- S. Shofiyah,* I. Narulita* and J. Sofjan~" *Research and Development Center for Geotechnology, Indonesian Institute of Sciences, J1. Sangkuriaug, Bandung 40142, Indonesia tDepartment of Biology, Bandung Institute of Technology, Indonesia Coral rich modem reefs fringe the north coast of East Timor and flanks the relatively steep slope of Wetar strait. This strait is strongly influenced by the Asian-Australian monsoon system that controls seasonal rainfall and sea surface currents. Solar insolation and fresh water recharge to the sea influence the reef environment by modulating variations in sea surface temperature and other physical and chemical conditions. Porites growth in the intertidal zone records sea surface conditions in its carbonate skeleton. Small, longitudinal slabs of Porites were collected from the north coast of East Timor. The growth pattern is clearly seen as alternating heavy and light banding of marine-terrestrial vulvic acid. Bleached, dead surface or disturbed growth is observed, but has been covered by younger carbonate banding. This pattern can be correlated to the historical climate record. Copyright © 1996 INQUA/Elsevier Science Ltd INTRODUCTION The Indonesian Arc Islands (Fig. 1) reflect a unique environment relating to regional and global climate change. The global current system of the Pacific and Indian Oceans pass through the deep straits and rise to the Sunda-Sahul continental platform (Fig. 2) bring- ing nutrients to the surface. The tropical monsoon system between Asia and Australia influences this area. '::!!!ii! The annual change in wind direction generates an oscillating upper current that distributes nutrients to the East Timor reefs. The large reef platform is free from suspended terrestrial material (Hantoro, 1993a, b). East Timor reefs (Fig. 3) are rich in massive corals that develop in shelter bays, primarily in the eastern part of the Indonesian Maritime Islands. A suitable environment for reef growth appears to have started when sea level rose rapidly (>6 mm. year-1) at about 6000 BP (Hantoro, NE8 PACIFIC OCF~AN -0" -10" INDIAN OCF.AN 0 lO001ml I I I 11111" I -10" ¢1 ";""-;.... ':~ I NEW ~:. " ~iiii~ otrt.~ .::;i $ ~i~iiili::::iii~i ..... iiiiiiiiiiili!ii , FIG. 1. Map of the Indonesian Arc Islands; the continental platform is stippled. 81