T155 Springs as Sites of Dynamic Physical, Geochemical, and Ecological Processes

Tuesday, 11 October 2011
8:00 AM - 12:00 PM
Room M100DE

THE EFFECTS OF SPRING LEVEL ON STROMATOLITE LAMINATION AND MORPHOLOGY, YELLOWSTONE NATIONAL PARK

Paper number: T155-13
Program: Technical Sessions
Time: 11:05 AM – 11:20 AM

Authors

Abstract

Siliceous stromatolites were collected from a hot spring in Yellowstone National Park in order to investigate environmental effects on stromatolite morphogenesis. Light-dark couplets comprised of weakly mineralized cyanobacterial filaments constitute the main body of the stromatolite. A less common style of lamination drapes the entire structure, contains coccoidal and filamentous forms and diatoms, and is well-cemented. During stromatolite growth, the main body style and the drape style lamination alternated.

In situ growth experiments coupled with micro-stratigraphic investigation of existing stromatolites suggest that the light-dark couplets are linked to rising water levels, whereas formation of the drape represents falling water levels/emergence. Overall, the structures grow a few cm per year. 14C analysis produced anomalously old ages versus the growth experiments, where the main body consistently contained lower Δ14C versus the drape fabric. When used as a tracer rather than an indication of age, the 14C data are consistent with the observations from the in situ growth experiments: as CO2 from the hydrothermal vent waters is likely radio-carbon dead, the main body formed deeper in the spring, resulting in a greater influence from spring derived CO2 during photosynthetic CO2 uptake, and the drape formed when the structure was emergent or nearly emergent, resulting in a greater incorporation of atmospheric CO2. 14C may be a particularly useful tracer for the uptake of CO2 from different sources in this, and perhaps other similar systems.

Several environmental factors may influence stromatolite growth in the spring. Hourly temperature logs from Obsidian Pool Prime record near-diurnal variability but also seasonal trends and storm-events which cool pool waters by >15°C enhancing SiO2 supersaturation. It is possible that the changing spring levels record larger-scale climatic and geologic processes in Yellowstone National Park.