Paleomagnetic Analysis of a Long-Term Sediment Trap, Kooken Cave, Huntingdon County, Pennsylvania, USA

Abstract

Kooken Cave is an extensive, deep fissure system developed in Ordovician age limestones of the Valley and Ridge physiographic province, Pennsylvania, USA. The cave floods to significant depth each year, due to influent surface waters. The cave drains slowly, and 45 ft (15 m) of clastic sediments fill portions of the cave. The discharge area for groundwater flowing through the cave is unconfirmed, but appears to be the Little Juniata River, which is steeply incised into the limestone upland containing the cave. The lowest deposits in the cave contain clay, sand, and cobbles, which probably limit draining of the cave. The remainder of the sediments are exclusively fine-grained. Twenty-four paleomagnetic samples were collected and analyzed. They all show normal polarity, indicating deposition within the present chron (< 780 ka). Sample pairs show good correlation, indicating that the sediments maintain a good record of paleosecular variation. Declinations are generally eastward of the present-day field, and most inclinations show shallowing. Sediment accumulation rates extrapolated from recent individual floods suggest that the entire sedimentary package could have been deposited within 1,440 years. Expected river incision rates and other geomorphic constraints lead to an age of <320 ka for the cave. It is likely that Kooken Cave has been accumulating allochthonous sediments for 1,000-10,000 years.