QUARTZ LUMINESCENCE FROM SOIL AND SAPROLITE: A TEST CASE FROM THE WESTERN PIEDMONT OF NORTH CAROLINA
Our study investigates soil and saprolite OSL samples from both shallow and deeply weathered soil profiles from 1-meter soil pits and 10+ m deep regolith cores in the Redlair Observatory near Charlotte, NC. We measure single-grain and small-aliquot LM-OSL to characterize luminescence signal components. Deconvoluting the luminescence signal is important for identifying the presence and intensity of the fast component and may indicate sedimentary maturity. The fast component takes time to evolve at the Earth’s surface, while non-fast components are not easily bleached by sunlight during sedimentary transport and are not preferred for luminescence age determination. Saprolite will not have undergone sedimentary transport or pedoturbation given the presence of in-situ bedrock foliation and thus we expect it to be dominated by non-fast signal components.
Our results show that LM-OSL measurements of saprolite have no fast component. Overlying soil horizons have variable luminescence intensity, with generally more signal from the fast component compared to saprolite. Upper soil horizons that have limited sensitivity and lack fast-dominated signals are either derived from in-situ materials, are less mixed, and/or recently eroded from saprolite. Similarly-classified soil horizons with more luminescence-sensitive quartz grains may suggest increased weathering, mixing, and/or greater input from distal sources.