UNDERSTANDING THE CLIMATE AND LANDSCAPE THAT LED TO EXCEPTIONALLY LARGE BURROWS IN THE UPPER DEVONIAN HUNTLEY MOUNTAIN FORMATION

The Huntley Mountain Formation is well-preserved in outcrop at the Red Rock Quarry locality in Ricketts Glen State Park, PA. These sediments represent deposition in the Upper Devonian (possibly Lower Mississippian). Thornburg et al. (2018) found multiple lungfish aestivation structures, including an extremely large burrow with similar morphology to these more typical burrows. Within this same horizon is a second large burrow unlike the lungfish burrows with entrance shaft and terminal chamber. This study will merge detailed sedimentological data from these burrows with bulk geochemistry and paleosol data from surrounding horizons to understand the landscape and climate during deposition of these sediments.

Modern lungfish use aestivation burrows as a refuge during seasonal dry conditions, reemerging when the landscape becomes sufficiently wet. Paleosols preserve surficial conditions during their formation, with indications of landscape stability and paleodrainage. This information on drainage provides evidence of wetting and drying that would indicate a fluctuating water table. Bulk geochemistry from these sediments provides additional evidence of drainage conditions with the ratio of Ba/Sr. Measured bulk geochemistry also offers insight into paleoprecipitation using the chemical index of alteration minus potash given by CIA-K = 100 x [Al­­₂O₃/(Al­­₂O₃+CaO+Na₂O)] with mean annual precipitation (MAP) defined by the relationship of MAP (mm · yr^-1) =221e^{0.0197(CIA-K)}. Salinization (S = (K+Na)/Al) also provides an approximate relationship with mean annual temperature (MAT) of MAT (°C) = -18.5(S) + 17.3.

Collectively this information synthesizes a picture of the depositional environment and potentially provides explanation for the development of these exceptionally large preserved burrows. The Huntley Mountain Formation occupies a unique space as it stretches across the Devonian-Mississippian boundary and preserves information on the environment and climate during this time.