Dr Alan Channing

The vent pool and sinter apron of Medusa Geyser at Norris Geyser Basin during an eruption. The shallow concentric pool visible adjacent to the vent was the site of in situ taphonomy experiments.

PhD Research

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).

My 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.

Silica (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. 

Collecting water temperature, conductivity and pH data in a thermally influenced stream. The stream contains dense carpets of Eleocharis flavescens.

Post-Doctoral Research

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:

l Attempted 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.

l Analysed water samples to reveal concentrations of nutrient, beneficial and phytotoxic elements available to plants and concentrations of silica available to fossilise vegetation.

l 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.

l Conducted taphonomy 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.

Geothermal 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 maritimum. Sinter chip levee banks within and at the margins of the run-off streams flowing into the wetland have sparse alkali and salt tolerant grasses.

My Current reasearch is attempting to track the history of hot spring ecosystems back through the rock and fossil record.