Short communicationA pluvial episode identified in arid Australia during the Medieval Climatic Anomaly
Introduction
The Medieval Climatic Anomaly (950–1250 CE) has classical climatic connotations for the Northern Hemisphere (e.g. severe drought in North America, Feng et al., 2008) and associated cultural developments (e.g. the settlement of Iceland and Greenland at ∼CE 874 and ∼CE 985, respectively; Xoplaki et al., 2011). A number of studies have examined the temporal and regional variation in the MCA for different regions, although almost exclusively within the Northern Hemisphere, and with no robust evidence for MCA hydroclimate impacts in Australasia. This time interval is however particularly notable in continental Australia because recent archaeological evidence suggests a rapid expansion in human population during and following the MCA (Smith and Ross, 2008; Williams et al., 2010). However, the role of climate in this expansion remains to be determined, and unlike the situation in the Northern Hemisphere, little is known as to whether this interval was warm, wet, cool or dry.
At a global scale, major shifts in climate at this time are hypothesised to be a result of a strongly positive North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) (Trouet et al., 2009), together with a shift towards a La Niña-like mean state in the Pacific (Clement et al., 1996; Mann et al., 2009). We assess the nature and timing of a major pluvial episode in southern central Australia that corresponds to the MCA by excavating relict shorelines and dating them with a range of independent dating techniques. We also examine the association between the hydrology and atmospheric circulation in southern central Australia.
Section snippets
Regional setting and methods
Lake Callabonna is part of the Lake Mega-Frome system (Lakes Frome, Callabonna, Blanche and Gregory, Fig. 1), which coalesces at 5 ± 2 m depth to form a single major waterbody surrounding the eastern and northern margins of the Flinders Ranges in arid central Australia (Fig. 1). These playa lakes have lake-floor elevations that range from −2 to +1 m Australian Height Datum (AHD – equivalent to mean height above sea level). Historically, Lakes Frome and Callabonna have filled to depths of
Chronology of the Lake Callabonna relict shorelines
The lake margin transect represents a relatively steep margin with four prominent shorelines above the modern floor, dissected by modern streams (Fig. 1). Five excavations were undertaken to supplement the original stratigraphic section undertaken by Cohen et al., 2011, Cohen et al., 2012 to test the validity of the initial MCA chronology. The additional stratigraphic sections confirm the presence of a 0.5–0.6 m thick beach unit from the lowest shoreline, which is 4 ± 0.2 m above the playa
Discussion and conclusion
Shoreline evidence for an MCA pluvial episode at Lake Callabonna is supported by studies documenting high-magnitude flooding in rivers draining the central Australian ranges (Pickup et al., 1988; Patton et al., 1993), the Barrier Ranges ∼150 km to the east of Lake Frome (Jansen and Brierley, 2004), and the Flinders Ranges, where at least one major flood has occurred since 300 CE (Quigley et al., 2007). Unlike the Flinders Ranges and Barrier Ranges, no record of major flooding occurs along the
Acknowledgements
This research was undertaken as part of ARC Discovery funding (DP1096911) to GCN and TJC. We would like to thank Gerard and Karina Sheehan of Moolwatana homestead for their hospitality and access to sites. We also thank the reviewers for improving the quality of the manuscript.
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2015, Quaternary Science ReviewsCitation Excerpt :The regional pattern depicted in Fig. 6 contrasts with opposite trends recorded in saline lakes in the Wimmera region of northern Victoria (Kemp et al., 2012) and an increase in dust transport from the Murray Darling Basin (Marx et al., 2011). In addition, exposed shorelines from the playa Lake Callabonna, South Australia, suggest a lake high stand occurred during the Northern Hemisphere's Medieval Climate Anomaly at a time when Western Victorian lakes were relatively dry (Cohen et al., 2012). Such spatial heterogeneity points towards a complex pattern of surface hydrology and seasonality across southeastern Australia, for which further data generation and synthesis are required for a more complete understanding (Gouramanis et al., 2013).
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2015, Quaternary Research (United States)Citation Excerpt :Four successively older and higher beach ridges were selected at the two localities of Salt Creek (SC) and Callabonna Spit (CS) along the southwestern shore of Lake Callabonna (Table 1, Figs. 1, 2). The chronology for the four studied beach ridges is based on a combination of single-grain OSL and 14C ages presented elsewhere (Cohen et al., 2012a, 2012b; Gliganic et al., 2014) and is broadly illustrated in Fig. 2 with details summarized in Table 1. On the crest of each of these beach ridges, which represents the most stable part of these landforms, a ~ 1.5 m by 3 m wide pit of 2–3 m depth was trenched with a mechanical excavator.