The Stripes of Donkerhuk
by John Clemens
This is a high dynamic range (HDR) photograph of an outcrop of the Early Cambrian Donkerhuk granite near Otjimbingwe in the Erongo region of Namibia. The granitic magmas intruded as literally thousands of subparallel sheets whose orientation in this locality was controlled by the magma feeder zone in the Okahandja Lineament and the flattening perpendicular to this, due to the 'soft' collision between the Congo and Kalahari Cratons. Although many, and perhaps most granitic intrusions are assembled from many relatively small injections or pulses of magma, preservation of these magma sheets is highly exceptional, so this body provides some unique insights into what is going on when batholiths are being constructed.
The HDR photograph was assembled from three separate exposures, spaced at 1.66 eV and then fused and tone-mapped into the final image. This technique is useful for bringing out subtle structures in the subjects, as well as for overcoming the unwanted contrast effects of burned-out highlights and deep shadows in some strongly lit scenes.
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John Clemens (distributed via imaggeo.egu.eu)