Testing the synchroneity of pollen signals using tephrostratigraphy

Since the advent of radiocarbon dating, the concept of synchronous pollen-v egetation events extending across broad regions such as the British Isles, which had emerged from earlier pollen-stratigraphic studies, has been large ly refuted. Nevertheless the assumption that pollen profiles within a geogr aphically coherent area should exhibit broadly comparable and synchronous p ollen signals still holds currency among some palynologists. This assumptio n is tested here by comparing pollen spectra between lateglacial and postgl acial sites in northern New Zealand, until recently unaffected by human act ivity, where independent correlations are obtained by tephrochronology. At sites of similar size, morphology, and depositional environment within the same phytogeomorphic region, it is possible to achieve accurate palynologic al correlations, provided local taxa and those representing ecologically di sparate source species are omitted from the pollen datasets. However, anoma lous correlations may still occur and are more likely when sites with diffe rent depositional environments or at greater distances are compared. These results suggest that the concept of synchronous pollen signals, even betwee n nearby sites with similar depositional setting, is not universally applic able and it is possible that erroneous palynostratigraphic correlations hav e been made in the past. (C) 1999 Elsevier Science B.V. All rights reserved .