Holocene climate recorded by magnetic properties of lake sediments in the Northern Rocky Mountains, USA

We present two hypotheses regarding the evolution of Holocene climate in the Northern Rocky Mountains that stem from a previously unpublished environmental magnetic record from Jones Lake, Montana. First, we link two distinct intervals of fining magnetic grain size (documented by an increasing ratio of anhysteretic to isothermal remanent magnetization) to the authigenic production of magnetic minerals in Jones Lake bottom waters. We propose that authigenesis in Jones Lake is limited by rates of groundwater recharge and ultimately regional hydroclimate. Second, at ~8.3 ka, magnetic grain size increases sharply, accompanied by a drop in concentration of magnetic minerals, suggesting a rapid termination of magnetic mineral authigenesis that is coeval with widespread effects of the 8.2 ka event in the North Atlantic. This association suggests a hydroclimatic response to the 8.2 ka event in the Northern Rockies that to our knowledge is not well documented. These preliminary hypotheses present compelling new ideas that we hope will both highlight the sensitivity of magnetic properties to record climate variability and attract more work by future research into aridity, hydrochemical response, and climate dynamics in the Northern Rockies.

Two new species of Hurleyella Runyon & Robinson (Diptera: Dolichopodidae), with the first record from the Neotropics

Two new species of the long-legged fly genus Hurleyella Runyon & Robinson, 2010 are described and illustrated: Hurleyella belizensis sp. nov. from Belize and Hurleyella salina sp. nov. from alkali areas of the Northern Rockies of the USA (Idaho, Montana, Wyoming). The discovery of these new species greatly extends the known distribution of Hurleyella northward in the Nearctic and southward into the Neotropics. Notes, photos of habitats, a distribution map, and a key to the four known species of Hurleyella are provided.

An analysis of spotting distances during the 2017 fire season in the Northern Rockies, USA

The wildfires that burned in the Northern Rockies region of the USA during the 2017 fire season provided an opportunity to evaluate the suitability of using broadscale and temporally limited infrared data on hot spot locations to determine the influence of several environmental variables on spotting distance. Specifically, correlations between the maximum observed spot fire distance for each unique combination of fire and day and geo-referenced environmental data on wind speed, vegetation, and terrain, along with specific fire characteristics (size, fire perimeter shape, and growth), were assessed. The data were also utilized to evaluate a popular theoretical model developed by Albini (1979) for predicting the maximum spotting distance for single and group tree torching. The results suggested a significant positive correlation between the maximum observed spot fire distance and an interaction between fire growth and wind speed. Significant negative correlations between maximum spotting distance and fire perimeter shape, canopy height, and terrain steepness were also discovered. The evaluation of Albini’s (1979) model suggested that selecting a high estimate of potential wind speed was important to minimize the likelihood of underpredicting maximum spotting distance.