A geomorphic framework for understanding the surface archaeological record in arid environments

Abstract

We present data from Australian study areas that support episodic nonequilibrium as a suitable model for developing a theoretical and methodological framework for interpreting the surface archaeological record. According to this model, long periods of little or no geomorphic activity are punctuated by catastrophic events that erode or deposit sediments, and hence remove or cover up surface stone artefact deposits discarded by Indigenous people in the past. We demonstrate the impact of a single rainfall event on the surface archaeological record at one of our western New South Wales study locations. We then use the results of Optically Stimulated Luminescence (OSL) of sediments underlying the artefact deposits and radiocarbon dating of associated heat-retainer hearths to suggest that both landscape chronology and the surface archaeological record are reflections of a series of episodic events such as this rain event. We conclude that, at least in our study area, the archaeological record is discontinuous in time because geomorphic events have removed the record equating to particular time periods. This process is cumulative so that the record of recent times is much more common when compared to that from earlier times. The episodic nature of geomorphic processes also has an effect on human behaviour, such that occupation of place is discontinuous. The methods by which the archaeological record is surveyed and interpreted need to take into account these spatial and temporal landscape discontinuities.

The surface archaeological record in arid Australia: Geomorphic controls on preservation, exposure, and visibility

“…The pre-European floodplain surface probably accumulated as slackwater deposition during erosion episodes (Jansen & Brierley, 2004) that occurred between 1530 and 960 years ago. Our optically stimulated luminescence (OSL) dating of sediments obtained from a shallow gully traversing the valley floor confirms this interpretation: Sediments within 30 cm of the surface are late Holocene in age and conform to Jansen and Brierley's erosion episodes 1 and 2 (Fanning, Holdaway, & Rhodes, 2007).…”

“…Episodic flood events, resulting in erosion in some areas and deposition in others, are a feature of our study area (Fanning, Holdaway, & Rhodes, 2007). Mean annual rainfall is relatively low, but variability is high (greater than 50%), and the bulk of the rain falls during short, intense rain depressions, especially in summer.…”

“…At one of our sampling locations, water overflowing from a shallow rill network created a new channel that removed surface sediments, including artifacts that we had surveyed just a few months before. However, at another location only a few kilometers away, the effects of the storm were not nearly so dramatic, with the main effect appearing to be an increase in vegetation cover (Fanning, Holdaway, & Rhodes, 2007).…”

“…Faced with these problems, and the lack of a geoarchaeological model of arid zone archaeological record formation, archaeologists have tended to take the record at face value: The ubiquity and age of the record indicates past population numbers, and the presence of an archaeological record can be interpreted using a conventional settlement pattern approach (Holdaway & Wandsnider, 2006). In this paper, we briefly review our twelve years of research in western New South Wales (NSW), Australia, which has used a framework based on a geoarchaeological assessment of the archaeological landscape and a targeted sampling strategy (Fanning, Holdaway, & Rhodes, 2007). We then present our most recent results that help to explain both the ubiquity of the record in certain locations and its absence in others, as well as its age, and discuss how the distribution of the record should be assessed.…”

The Effects of Holocene Landscape Changes on the Formation of the Archaeological Record in the Fayum Basin, Egypt

“…We use a geoarchaeological approach adapted specifically to arid environments (Fanning et al, 2007(Fanning et al, , 2008(Fanning et al, , 2009Holdaway & Fanning, 2014) to understand the nature of erosion and aggradation that shape today's desert land surfaces, and therefore how these processes impact on the visibility of the archaeological record. We combine detailed topographic survey with studies on sediments (grain size analysis, thermogravimetrical analyses (TGA)) and artifact concentrations, including chronometric data from secure archaeological contexts (AMS 14 C dates on charcoal from hearths).…”