I used the active hot spring environments of Yellowstone National Park as
analogues for ancient systems. As a PhD student I conducted plant
taphonomy experiments that investigated patterns of plant
preservation/decay and fabrics and processes of silica deposition. These
revealed that colloidal processes dominate silica deposition within
plants as silica precipitates most readily from hot spring waters as
opal. This takes the form of micron-scale spheres which are subject to
colloidal forces such as flocculation, coagulation and gelation. These
produce very distinctive networks of silica particles and solid silica
films and blocks which stabilise plant tissues against collapse (Channing & Edwards 2004).
experiments also revealed that protracted periods of water-logging are
required for high quality preservation of plant tissues. In Yellowstone this is most often achieved in cool wetland habitats that form at the margins of hot spring areas (Channing 2003). I hypothesised that the excellent preservation of large numbers of plants at Rhynie occurred in a geothermal wetland (Channing et al 2004)
as most hot spring environments only support sparse vegetation whilst
geothermal wetlands support relatively lush vegetation which live and
die immersed in silica rich hot spring waters.
(opal-A) permineralised vascular bundle and fibre sheaths of the
wetland plant Eleocharis rostellata. This sample was preserved following
11 months immersion in the aron pool of Medusa Geyser at Norris Geyser
Basin. Cell preservation in three dimensions is evident across the
entire image and cells are variously lined with silica and infilled by
networks of opal-A spheres.
water temperature, conductivity and pH data in a thermally influenced
stream. The stream contains dense carpets of Eleocharis flavescens.
During my first post-doc I investigated active geothermal wetlands of Yellowstone (Channing & Edwards 2009).
My research had a broad focus but the principal aim was to investigate
the ecophysiology of the Rhynie Chert plants via analogy with vegetation
of active geothermal wetlands. In order to achieve this I:
to characterise the physical and chemical environment of active
wetlands using data-logging equipment and probes that measured basic
parameters which affect plant colonisation and growth including
-conductivity, redox, pH and temperature.
samples to reveal concentrations of nutrient, beneficial and phytotoxic
elements available to plants and concentrations of silica available to
Investigated the sedimentology of active Yellowstone geothermal wetlands, plus similar environments in New Zealand, Iceland and Chile and compared observations with fossil examples in Queensland, Australia and Santa Cruz Province, Patagonia to provide models that can be tested against the Rhynie Chert.
experiments which investigated patterns of plant decay/preservation and
silica deposition which were then compared to other hot spring
environments including vent pools, sinter aprons and run-off streams.
These allowed comparisons of plant preservation potential between high
and low temperature and wet and dry environments which revealed
environment specific taphonomic fabrics.
wetland developed where hot spring waters flow from Big Blue Hot Spring
into the northern margin of Elk Park, Yellowstone National Park. The
wetland vegetation is dominated by the hydrophytic, salinity and
alkalinity tolerant plants Eleocharis rostellata and Triglochin
Sinter chip levee banks within and at the margins of the
run-off streams flowing into the wetland have sparse alkali and salt
My Current reasearch is attempting to track the history of hot spring ecosystems back through the rock and fossil record.