Garniss Curtis (1919–2012): Dating Our Past

Abstract

Garniss was field-oriented and critical. He did not promote lab-perfect dates if they were misapplied. {\lq}{\lq}OH 9 could just as easily have come from Bed IV as Bed II. It was in the bottom of a gully,{\rq}{\rq} Garniss once told me in reference to a Homo erectus calvaria (partial cranium) from Olduvai Gorge. The distinction was important because most experts assume the calvaria was from Bed II, hundreds of thousands of years older than Bed IV. Garniss suspected the calvaria could be much younger because he was there. And {\lq}{\lq}being there{\rq}{\rq} is what made this amazing man the conduit of knowledge that he was. Although it may seem a laboratory-specific endeavor, dating volcanic tuffs and the fossils and artifacts they bound takes much more than a mass spectrometer, a vacuum furnace, and a scientist in a lab coat. The lab work is certainly an essential part of things---and Garniss did it well---but there are countless non-intuitive depositional environ- ments and processes associated with volcanism: violently projected air-fall ashes, massive floods of lava, ferocious flows of superheated, liquefied ash surging across large landscapes, pumices floating down ash-choked mud streams, and all sorts of waterways carrying and depositing ash-laden silts. Volcanic deposits are famously easy to misinterpret in the field. Replicability in radiometric dating thus means much more than just sending multiple samples of the datable ash through competing labs; it means that the sample must first be properly collected and interpreted in its place, a crucial aspect of the job invisible to most who don{\rq}t do fieldwork.