Rock varnish microlamination dating

In contrast, the rock varnish is greatly enriched in Mn relative to the stone and to a lesser degree in Pb, Ca, Zn, Cu and Ni.Cross sections of the black encrusted regions show that the stone’s red coloration has been modified by black pigmentation from the surface down to ~250 μm.The Smithsonian Institution Building, commonly referred to as the Castle, is located on the National Mall in Washington, DC, and was constructed in the mid-nineteenth century for the purpose of housing all museum and scientific functions for the newly formed institution.Matching gateposts designed by the Castle’s architect were erected more than a century later in the Enid A. Black patches were recently noted on both structures, which are clad with locally quarried Seneca red sandstone.

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At the same time, rock varnish was viewed holistically within a new framework.Bulk rock and varnish chemistry, in addition to microscopy and microanalysis of the varnish, are presented here.On a bulk chemical basis, the Seneca sandstone is relatively poor in Mn, containing ~500 ppmw.Rock varnish microlamination (VML) dating uses the slow buildup of 'varnish' or dark coating on subaerially exposed rock surfaces.It is the world's slowest-accumulating sedimentary deposit at around ~1μm per 1000 years.