GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 341-38
Presentation Time: 9:00 AM-6:30 PM

A GEOLOGIC GUIDE TO SHIKELLAMY STATE PARK (OVERLOOK AND MARINA SECTIONS): UNION AND NORTHUMBERLAND COUNTIES, PA


ELICK, Jennifer M., Earth and Environmental Sciences, Susquehanna University, 514 University Avenue, Natural Sciences Center 111C, Selinsgrove, PA 17870, elick@susqu.edu

Located on Blue Hill and along the Susquehanna River, Shikellamy State Park is split into two sections: the Overlook and Marina sections. The Overlook Section provides a spectacular view of the central Susquehanna River Valley above the confluence of the north and west branches of the Susquehanna River; the Marine Section is a direct access point to the river at the confluence.

Situated in the Valley and Ridge Province of Pennsylvania, the park is part of a large syncline that connects to a distant anticline at Montour Ridge. The ridge forms the northern horizon from the Overlook, is composed of Tuscarora Formation (Silurian), and is twice as high as the Overlook. The Overlook provides an incredible view of the the landscape and a great example of regional erosion.

An exposure of the Sherman Creek Member (Catskill Formation-Late Devonian) can be directly accessed along County Line Road, as one approaches the Overlook section entrance. At the base of the cliffs, a multistoried, greenish-gray sandstone contains abundant carbonized Archaeopteris branches, cross strata, and some malachite. The cliffs above are mostly reddish-grey and contain interbedded floodplain overbank deposits and paleosols. Some multistoried reddish grey channel sandstone contain clay-lined Archaeopteris branches and root traces.

From the Overlook, one can also view the confluence between the North and West Branches of the Susquehanna River. The sediment-rich North Branch drains a region greatly influenced by Pleistocene glaciation. Much of the sediment in this branch is due to the erosion of glacial deposits. The Marina Section is situated on Packer Island, an island in the North Branch that has been mapped as Recent to Late Illinioian stratified drift. The drift overlies the Sherman Creek Member.

Although the park has many visitors who enjoy hiking, the scenery, and boating access to the river, little is known about this park and it’s outstanding natural features and geology. This guide highlights some of the historical and geological elements of the park that may be of interest to curious visitors. It may help visitors appreciate the paleogeographic and paleoenvironmental/paleoecological changes within the Appalachian Basin over time and recent landscape evolution.