PARAMETERS ASSOCIATED WITH MODERN STROMATOLITES IN SPRING-FED STREAMS OF DEATH VALLEY NATIONAL PARK

Stromatolites have a rich fossil record, yet are rarely found in modern environments. In Death Valley National Park (DEVA), stromatolites with incipient mineralization thrive in some spring-fed streams forming carpets, terraces, and domical buildups. We compare environmental conditions among streams with dense stromatolite growth to those where stromatolites are rare or absent. Results are factors that may control stromatolite growth and survival in the harsh environments of DEVA with possible application to Mars, and best practices for monitoring and protecting one of DEVA’s enigmatic organisms.

We selected a 10m long branch of Keane Wonder Spring. Multiple overlapping, georeferenced images of the stream (GoPro Hero 10 on a handheld monopod) were used to generate a digital elevation model (DEM) with OpenDroneMap software. Analysis gave quantitative measures of stream gradient and stromatolite growth density. Dissolved ion concentrations, pH, and temperature were plotted on the DEM. Relationships between the physical and chemical conditions and stromatolite density and morphology were evaluated and compared among stromatolites-bearing and -free spring-fed streams in DEVA.

Several associations between stromatolite characteristics and environmental parameters were apparent in the Keane Wonder Spring stream. All water samples are alkaline (8.3-9.2) and are sodium chloride sulfate-dominated. 1) Stromatolites are generally absent in shaded areas or where abundant green algae occur. 2) Shallow stream sections with higher flow velocity are preferentially inhabited by small (1-10mm diameter) mat or terrace-forming laterally linked hemispherical heads. 3) Larger (10-50cm) domical heads are the predominant morphology in splash zones of waterfalls and cascades. 4) Stromatolite density is inversely related to calcium ion concentration. However, these associations are perfectly correlated at all localities, despite the similarities in water chemistry.

Identification of conditions that favor and hinder stromatolite growth in the extreme temperature and insolation of DEVA contributes to our understanding of stromatolites through time and space, highlighting the most favorable conditions for stromatolite development at locations decidedly unfavorable to most lifeforms.