“Difference Dating”: A novel approach towards dating alpine glacial moraines

The East Antarctic Ice Sheet responds sluggishly to shifts in climate. To capture subtle changes in Antarctic climate, researchers have focused instead on smaller alpine and cirque glaciers that fringe the ice sheet throughout the McMurdo Dry Valleys. The exposure ages of glacial moraine boulders scatter widely and often incorporate large amounts of inheritance, prohibiting the construction of a regional deglaciation chronology. We present a new sampling technique that takes advantage of ubiquitous desert pavements and allows for the detection of inheritance in overlying glacial moraine boulders. Our approach requires a large sample set, but offers increased confidence in modeling moraine age, an acceptable trade-off considering the need for more refined Antarctic paleoclimate reconstructions. Using the beryllium-10 system in sandstone quartz, we show that single exposure ages collected from moraine boulder tops are frequently inaccurate, and consistently over- and underestimate moraine age. Difference Dating offers a new approach to dating alpine glacial moraines independent from traditional boulder exposure age dating.