Rock varnish microlamination dating daytonabeach dating com
In this study, we establish a generalized late Pleistocene (18–74 ka) millennial-scale microlamination sequence in fine-grained, fast-accumulating rock varnish for the drylands of western USA, radiometrically calibrate the sequence and correlate it with the δ¹⁸O record in the GISP2 Greenland ice core.We then use this climate-correlated varnish microstratigraphy to estimate surface exposure ages for radiometrically dated late Pleistocene geomorphic features in the study region.The VML and ³⁶Cl dating of the distal Q2c fan surfaces on Hanaupah Canyon fan reveal two episodes of large-scale fan aggradation ended at 72 24/− 20 ka and 73.55 ka during the wet period of MIS 4.Fanhead incision and associated within-channel or fantoe aggradation are found to take place during the relatively dry period of the glacial-to-interglacial climatic transition (12–24 ka) and the Holocene interglacial dry period (0–12 ka).The VML dating of distal Q2c fan surfaces on Hanaupah Canyon alluvial fan in Death Valley, California, yields a minimum-limiting age of 73.55 ka, in accord with cosmogenic ³⁶Cl depth-profile ages of 66 22/−14 ka and 72 24/−20 ka for the same fan deposits.
The VML dating of a small tributary fan in Death Valley reveals two episodes of fan aggradation, one ceasing at 73.55–86.75 ka during the dry period of the last interglacial (MIS 5a) and the other finishing at 66.15 ka during the wet period of the last glacial (MIS 4).
Just about any rock type will accumulate varnish, in so long as rock-surface erosion is slow enough to permit varnish accretion.
Varnish microlamination (VML) dating is a climate-based correlative age determination technique used to correlate and date various geomorphic features in deserts.
The VML dating of a giant ejecta block on the rim of Meteor Crater in northern Arizona yields a minimum-limiting age of 49.15 ka, closely matching a thermoluminescence (TL) age of 49 ± 3 ka and slightly younger than a recently updated cosmogenic Cl age of 56.0 ± 2.4 ka for the meteor impact event.
The VML dating of distal Q2c fan surfaces on Hanaupah Canyon alluvial fan in Death Valley, California, yields a minimum-limiting age of 73.55 ka, in accord with cosmogenic 14 ka and 72 24/− 20 ka for the same fan deposits.