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A long record of environmental change from bat guano deposits in Makangit Cave, Palawan, Philippines

Published online by Cambridge University Press:  01 March 2007

Michael I. Bird
Affiliation:
School of Geography & Geosciences, University of St Andrews, St Andrews Fife KY16 9AL, Scotland, UK. E-mail: michael.bird@st-andrews.ac.uk
Ella M. Boobyer
Affiliation:
School of Geography & Geosciences, University of St Andrews, St Andrews Fife KY16 9AL, Scotland, UK. E-mail: michael.bird@st-andrews.ac.uk
Charlotte Bryant
Affiliation:
NERC Radiocarbon Laboratory, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, Glasgow G75 0QF, Scotland, UK
Helen A. Lewis
Affiliation:
Institute of Archaeology, University of Oxford, 36 Beaumont Street, Oxford OX2 6LB, UK
Victor Paz
Affiliation:
Archaeological Studies Program, Palma Hall Basement, University of the Philippines, Diliman, Quezon City 1101
W. Edryd Stephens
Affiliation:
School of Geography & Geosciences, University of St Andrews, St Andrews Fife KY16 9AL, Scotland, UK. E-mail: michael.bird@st-andrews.ac.uk

Abstract

We present the first record of Holocene and Pleistocene environmental change derived from the chemical and stable-isotope composition of a tropical cave guano sequence from Makangit Cave in northern Palawan (Philippines). The 180 cm sequence of guano, derived predominantly from insectivorous bats and birds, consists of two distinct units. An upper section of reddish-brown oxidised guano to 110 cm was deposited since the mid-Holocene while a lower section of black, reduced guano was deposited through the Last Glacial Maximum (LGM) to >30 000 BP. Carbon-isotope (δ13C) values in guano deposited during the LGM are as high as −13·5‰ indicating that a C4-dominated grassland existed in the area around the cave at this time. Guano δ13C values of − 25‰ to − 28‰ suggest that this open vegetation was replaced by C3-dominated closed tropical forest, similar to that of the present, by the mid-Holocene. The results suggest that the climate of northern Palawan was substantially drier at the LGM than is currently the case.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 2007

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