[sup.230]Th Dates for Dedicatory Corals from a Remote Alpine Desert Adze Quarry on Mauna Kea, Hawai'i

Article excerpt

The authors show how sites in upland Hawai'i may be dated using uranium series radiogenic

measurements on coral. The sites lie in a quarry, inland and at high altitude, with little

carboniferous material around, and radiocarbon dating is anyway problematic here for the first

millennium. Freshly broken coral had been transported to these sites, remote from the sea- no

doubt for ritual purposes. Giving a date in the fifteenth century with an error range of only five

years, the method promises to be valuable for the early history of the Pacific.

Keywords: Pacific, Hawai'i, uranium, thorium dating, coral, ritual

Introduction

High precision dates for archaeological sites and major events in Hawaiian prehistory using 230Th dating of well-preserved branch coral (Pocillopora spp.) have been obtained in recent studies (Kirch & Sharp 2005; Weisler et al. 2006). 230Th dating holds the potential to revolutionise models of lowland settlement patterns and socio-political change given the common occurrence of branch coral in coastal sites, where it is interpreted as a religious offering based on ethnographic analogy (Handy 1927; Malo 1951). Because the radiocarbon calibration curve for late Hawaiian prehistory (about AD 1500-1778) is problematic with wide fluctuations often rendering large age spans that do not precisely date single events (Weisler et al. 2006: 273), 230Th dating, with typical 2 sd errors of <5 years, offers new insights into defining significant events in Hawaiian prehistory. How applicable 230Th dating will be in developing refined chronologies for sites located above the limits of agriculture and permanent settlement remains to be seen, but branch coral has been recovered in extremely remote areas. The epitome of long-distance transport of ritual offerings in Hawai'i is the Mauna Kea Adze Quarry Complex, on the island of Hawai'i (Figure 1), where various kinds of offerings, including branch coral, have been found at ~3750m elevation and more than 45km from the sea. The Mauna Adze Quarry Complex is the largest Neolithic quarry in the Pacific and the long-term use and intensity of adze manufacture is thought to mirror significant changes in Hawaiian socio-political organisation, including the development of craft specialisation. This paper presents the first dates for this remote, high elevation quarry using the 230Th dating technique.

Background: the Mauna Kea Adze Quarry Complex and its context

The Mauna Kea Adze Quarry Complex, which was placed on the National Register of Historic Places as a National Historic Landmark in 1962, is one of the most remote archaeological site complexes in Hawai'i. The nearest permanent settlements in the pre-contact era (pre-1778) were ~45km distant, as 'the crow flies,' on the windward side of the island. The actual distance would, of course, have been even greater, in the ascent to the main quarry area, which is located near the 3750m elevation on the south flank of the mountain not far below the 4206m-high summit. Some discrete quarry areas are located in a sub-alpine forest, bur most of the quarry complex is in a stony alpine desert, which has been characterised as a 'non-subsistence' environment because of the degree of biotic impoverishment and lack of food and fuel for fires (McCoy 1990).

Archaeological investigations of the Mauna Kea Adze Quarry Complex, in 1975-76 (McCoy 1977, 1990; McCoy & Gould 1977), indicate that it covers more area and contains a larger volume of debitage than all of the other known basalt adze quarries in the Hawaiian Islands combined. The structure of the Mauna Kea quarry 'industry' was inferentially more complex than any of the other quarries, based on the number and variety of activity remains. Recent investigations in the Pohakuloa Gulch area of the quarry indicate a number well in excess of the 264 workshops and 1566 individual chipping stations, 50 rockshelters, 200 open-air enclosures and 45 shrines, several panels of petroglyphs and pictographs and a local source of low-grade volcanic glass described in an earlier report (McCoy 1990: 96-7). …