Hydrogeomorphic controls on Holocene lacustrine loss-on-ignition records

Abstract

Holocene loss-on-ignition (LOI) records were developed for radiocarbon-dated sediment cores from 20 lakes in the Uinta Mountains of northeastern Utah, USA. The hydrogeomorphic setting of each lake was characterized, permitting an analysis of connections between LOI values and lake setting. Median LOI values exhibit a significant negative correlation with lake elevation, with the range of elevations and the maximum slope of the watershed, with the extent of ice/snow and exposed rock in the watershed, and with the volume of through-flowing water. In contrast, LOI is positively correlated with the extent of forest cover and wetlands in the watershed. In addition, forward stepwise linear modeling demonstrates that lake area/lake depth ratio is a significant negative predictor for median LOI, that shoreline complexity is a significant positive predictor for maximum LOI, and the standard deviation of LOI values is greater in lakes surrounded by watersheds with more wetlands and surface water. Some LOI time series contain excursions at finer temporal scales that are recorded synchronously in adjacent lakes, however many excursions appear in only a single record. Similarly, step changes in LOI that are clear in some records are not preserved in the sediments of nearby lakes. Over longer timescales, some LOI records are essentially constant during the Holocene. In contrast, some lakes record steadily rising LOI values, and approximately half of the lakes have complicated LOI records with millennial-scale variability. Lakes with large surface area, large area/depth ratios, large watershed area/lake area ratios, rugged watersheds, and extensive ice/snow cover are more likely to record steady LOI values over time. The degree to which LOI records from neighboring lakes vary emphasizes that lacustrine proxy records reflect a strong filtering effect, whereby the signal of an external forcing is recorded to varying degrees depending on the nature of the lake and surrounding watershed.