Abstract

Silicification of higher plants associated with active, alkali-chloride hot springs in Yellowstone National Park, Wyoming, USA, occurs dominantly in areas of geothermally influenced wetlands. Plants grow in an environment with many of the characteristics of an oligosaline marsh and are subjected to brackish salinity and high pH, temperature, silica, and heavy metal concentrations. As such, the plants undergoing silicification at Yellowstone are predominantly those more typically found colonizing widespread evaporation-driven inland waters and coastal salt marshes (e.g., Eleocharis rostellata, Triglochin maritimum) and are in some ways preadapted to hot-spring settings. This paper documents hydrochemistry and physical parameters in a typical geothermally influenced wetland at Big Blue Hot Spring, Elk Park in Yellowstone and records the taphonomic processes involved in silicification of the most common wetland plant Eleocharis rostellata. Silicification of plants in situ results in the three-dimensional preservation of tissues and cells characteristic of plants preserved around the Lower Devonian Rhynie chert hot-spring system. Sinter deposition at active and fossil hot-spring areas is typically associated with alkali-chloride springs above low-sulfidation epithermal systems. As mineralogical and geological evidence indicates that such a system was responsible for preservation of the Rhynie plants, it is hypothesized that they too, at least periodically, withstood comparable physiological stresses to the modern analogs.

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