A Lichenometric Dating Curve and Its Application to Holocene Glacier Studies in the Central Brooks Range, Alaska

Abstract

Lichen growth curves for dating in the central Brooks Range were developed and applied using Rhizocarpon geographicum s.l. and the fast-growing Alectoria minuscula/A. pubescens. Rhizocarpon eupetraeoides and R. inarense, nearly as common in this region, have a growth pattern which correlates with that shown by the R. geographicum curve for thallus diameters up to 150 mm. The R. geographicum curve has a great growth period lasting 200 yr based on historic, dendrochronologic and direct measurement control; this is followed by a linear growth phase of .apprx. 3 mm/century based on radiocarbon dates. The lichenometric technique has proved successful in developing the 1st detailed Holocene glacial chronology for the Brooks Range and indicates that major pulsations of cirque glaciers occurred as recently as 350 yr ago.