FILLED BURROWS FILL GAPS IN THE ROCK RECORD: AN EXAMPLE FROM A LATE DEVONIAN LUNGFISH BURROW AND HOST ROCK, CATSKILL FORMATION, LYCOMING COUNTY, PENNSYLVANIA

Passively-filled burrows can capture and preserve details regarding a depositional event that would otherwise be lost. A laterally extensive, massive, very fine sandstone layer approximately 50 cm in thickness is exposed along Pine Creek, 4 km downstream of Blackwell, PA. This sandstone is within the Late Devonian Catskill Formation and contains a dense fabric of root traces (1-2 mm in diameter), as well as an exceptionally preserved vertical burrow that is elliptical in cross section (Hyperoeuthys teichonomos; 15 cm in long-axis diameter, 45 cm in length) and is interpreted as a lungfish aestivation burrow. The very fine sandstone and vertical shaft are overlain by a finely laminated, micaceous mudstone at a sharp contact with no evidence of erosion. Due to the relative proximity with a cross-bedded, channel sandstone, the depositional environment of both the massive very fine sandstone and overlying laminated mudstone is interpreted to be a floodplain, but the cause for the abrupt transition between the very fine sandstone and mudstone is not evident. However, a detailed sedimentological investigation of the passively-filled abandoned lungfish burrow beneath the laminated mudstone reveals a more complete stratigraphic record. The bottom 5 cm of the burrow contain bed-parallel, highly angular clay clasts (up to 10 mm in length) with normal grading into coarse to medium sand. The fining-upward sand extends for ~8 cm and is overlain by a layer (16 cm thick) of subangular clay clasts (up to 8 mm in diameter) that contains disarticulated fish remains. This layer further fines upward into a siltstone. The whole sequence of passive infilling of the burrow is overlain by the laminated micaceous mudstone. Thus, the abandoned lungfish burrow contains a record of the sedimentary history between the massive very fine sandstone and laminated mudstone that would not have been otherwise preserved. We conclude that the laminated mudstone was deposited on a cohesive very fine sand deposit during the waning period of a flood event with multiple pulses that were capable of transporting coarse sand and cm-scale lithic clasts. This study demonstrates the importance of utilizing trace fossils in high-resolution sedimentological investigations.