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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)


Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes
Vol. 67 (1997)No. 5. (September), Pages 805-814

Silica-Cemented Beachrock from Lake Taupo, North Island, New Zealand

Brian Jones (1), Michael R. Rosen (2), Robin W. Renaut (3)


Beachrocks on the north coast of Lake Taupo are composed of volcanic grains and diatoms that are bound together by isopachous, meniscus, or pore-filling amorphous silica cements. The littoral sediments were originally stabilized by epilithic and chasmolithic filamentous microbes that bound neighboring grains together. The amorphous silica cement was precipitated from silica-rich geothermal fluids that originated from warm-water plumes that form in the northern part of Lake Taupo where hot spring waters flow into the lake and move along the shoreline. Water from the warm water plumes that is washed onshore by prevailing winds and currents then percolates down through the beach sands and gravels. Precipitation of amorphous silica, triggered by cooling of the mixed spring and lake water, is preferentially focused on the epilithic and chasmolithic filamentous microbes, which act as templates for silica nucleation and precipitation.

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