Calcrete Field Trip 2021 - Liesle Rd
Park vehicles carefully along the roadside or in nearby WDFW lots.
Touchet Beds unconformably overlie a calcrete at Liesle Road. At least one early scabland flood (pre-Wisconsin?) moving overland in a broad, shallow sheet, scoured the surface free of loess down to the armoring calcrete. Some loess then re-accumulated. Later floods (Late Wisconsin), following different, probably deeply-incised scabland routes to the west deposited only slackwater silts and sands (backflood rhythmites) at this location. The lowest Touchet Bed is very silty and appears to contain a significant amount of reworked loess. Early scour is the result of south-moving floods. Later deposition of rhythmites is due to ponding behind Wallula Gap and backflooding of eastern Quincy Basin. We are near the northmost limit and highest shoreline of Lake Lewis. The floodway evolved through time.
A few tapering, sheeted clastic dikes sourced in the Touchet Beds descend through the underlying calcrete and are truncated at their tops by the modern soil (Holocene), which contains a conspicuous white Mount St. Helens 1980 ash.
Calcrete exposed low in the Liesle Rd cuts shows evidence of both pedogenic development and groundwater influence. Look closely to locate the top of the lacustrine parent material. Does it correspond with the top of the calcrete? Is there more than one parent material?
Links to Other Stops:
Lind Coulee Fault at O'Sullivan Reservoir https://www.skyecooley.com/single-post/lind-coulee-fault-at-o-sullivan-reservoir