Globalization of tephrochronology: new views from Australasia

Abstract

Tephra (or volcanic ash) studies, once confined largely to volcanic lands, have become increasingly practised in countries far removed from areas of active or recent volcanism – and Australia is no exception. At the International Union for Quaternary Research (INQUA) conference in Cairns in July/August 2007, Sarah E. Coulter (née Davies), now a postdoctoral ice-core tephrochronologist at Queen’s University Belfast, reportedthe first occurrence of an exotic tephra in Australia in a core from Lynch’s Crater, Atherton Tableland, Queensland (Figure 1). The distal tephra, manifest as a tiny concentration of glass shards, was probably derived from a Papua New Guinean eruption around 75,000–80,000 years ago (S.E. Davies et al., 2007). Its value lies in providing a precise chronostratigraphic marker that potentially allows correlation of other long palaeoenvironmental sequences over wide distances. Davies’ study is but one of a revolutionary development in tephrochronology now focused on detecting diminutive, distal tephras that are invisible in the field and referred to as cryptotephras. From the Greek word kryptein, meaning ‘to hide’ (Hunt, 1999a; Hunt and Hill, 2001; Lowe and Hunt, 2001), cryptotephras typically comprise fine-ashsized (< ~100 μm) glass shards sparsely preserved and ‘hidden’ in peats or in lake, marine or aeolian sediments, or in ice cores (Figure 2). The cryptotephra theme is continued in section III, but beforehand nomenclature associated with the term ‘tephra’, which can be confusing and which sometimes is used incorrectly, is outlined.