Using OSL to assess hypotheses related to the impacts of land use change with the early nineteenth century arrival of Europeans in south‐eastern Australia: an exploratory case study from Grabben Gullen Creek, New South Wales

Abstract

A common explanation for intense soil erosion and gullying in SE Australia is the introduction by Europeans of new land use practices following their arrival in Australia in the late 18th century. Eucalyptus woodlands were cleared to introduce farming, and valley bottoms, characterized by chains of ponds with organic‐rich swampy meadow (SM) soils, were subsequently buried by thick deposits of ‘post‐settlement alluvium’ (PSA) generated by erosion in the catchment. In this study, optically stimulated luminescence (OSL) is used to evaluate the source(s) of the PSA in Grabben Gullen Creek (GGC), Australia. We use a portable OSL reader to measure total photon counts on bulk polymineral and polygrain‐size samples from nine profiles along the Creek. We use these luminescence signals as geotracers of sediment source(s) and transport pathways. We obtained higher luminescence signals in the PSA than in the SM sediments, suggesting different sources and fluvial transport conditions for these two widespread sedimentary units. Portable OSL reader data from soils in the GGC catchment that are potential sources for the SM sediments and PSA show that the high luminescence signals recorded in the PSA are similar to those from subsoil samples in granite soils, suggesting that the PSA was derived by gullying of granite subsoils. In the SM sediments, luminescence signals decrease upwards from the base of the profile, as expected in well‐reset fluvial deposits, but with one or more changes in gradient in the profile of photon counts with depth, most likely indicating changes in sediment deposition rates. To calculate deposition rates in the SM sediments, several samples were dated using OSL. The OSL ages produced low scatter in the equivalent doses, confirming the well‐reset nature of the grains composing the SM and indicating a process of sediment transport in dilute flows, as is interpreted from the portable OSL signals. Copyright © 2014 John Wiley & Sons, Ltd.

Instant luminescence chronologies? High resolution luminescence profiles using a portable luminescence reader

“…Inter sample variability and how quickly the POSL signal depletes has also been used to indicate whether sediments are well or poorly bleached (e.g. Kinnaird et al 2012;Muñoz-Salinas et al 2012;Muñoz-Salinas et al 2014). This current study shows that where samples are both recent and from a depositional context with poor bleaching,intersample variability can not be accounted for in this way.…”

Timing of post-European settlement alluvium deposition in SE Australia: A legacy of European land-use in the Goulburn Plains

“…Down-profile trends of bulk sediment OSL measurements from the six sample sites are similar to those measured through SM and PSA deposits elsewhere in the Tablelands (Muñoz-Salinas et al, 2014;. Both IRSL and BLSL at each profile decrease upwards through SM sediment and increase abruptly in the basal PSA ( Figure 3).…”

“…All catchments are arranged generally from South to North. Data comes from this study, Erskine and Melville (1984), Eyles (1977aEyles ( , 1977bEyles ( , 1977c, Gillespie (1981), Gillespie et al (1992), Muñoz-Salinas et al (2014), Prosser (1991, Prosser and Abernethy (1996), Rustomji and Pietsch (2007), Starr (1989) and Wasson et al (1998). Vertical dashed grey lines group samples from the same sediment profile.…”

“…Gully incision in upstream reaches of river catchments deposited mantles of PSA in valley bottoms, burying SM environments for up to tens of kilometres downstream (Muñoz-Salinas et al, 2014;Rustomji and Pietsch, 2007), a process that created a common valley bottom stratigraphy throughout the region consisting of dark clay-rich SM sediments overlain by the light-coloured and sandy PSA. This common stratigraphy has been subsequently exposed in gully walls by further stream incision into valley bottoms (Figure 2; Supplementary Figure 1, available online).…”

Combining bulk sediment OSL and meteoric10Be fingerprinting techniques to identify gully initiation sites and erosion depths

“…In the Tablelands region of southeastern Australia (Figure ), the causes and timing of gully incision and the connection between gullying and PSA deposition have been at the center of research efforts for decades [ Crouch , ; Eyles , ; Mould and Fryirs , ; Muñoz‐Salinas et al ., , ; Neil and Fogarty , ; Olley et al ., ; Olley and Wasson , ; Portenga et al ., , ; Prosser and Slade , ; Rustomji and Pietsch , ; Starr , ; Wasson et al ., ]. Catchment conditions and land use practices leading to initial gully incision are often not considered [ Prosser and Slade , ; Prosser and Winchester , ], although they are generally understood to involve vegetation disturbance along valley sides and bottoms, like those imposed by arid climate conditions or those introduced by European settlers in the 19th and 20th centuries [ Eyles , , ; Portenga et al ., ; Prosser , ; Rustomji and Pietsch , ; Scott , ; Starr , ; Zierholz et al ., ].…”