of the Palisades. It was determined later in the 20th century that the hill was composed of extrusive basalt with a minimum thickness of 125 ft (38 m). However, by 2011 it was known that the outlier, once considered to consist only of a single type of basalt, is more complex than originally thought. The outermost part of the outlier is composed of an elongated arc of Orange Mountain Basalt. Lying within this arc and stratigraphically above it is a band of sedimentary rock from the Feltville Formation. Finally, lying within and above the band of sedimentary rock is a central area of Preakness Mountain Basalt which constitutes the portion of the outlier reduced by quarrying. New Germantown Outlier The New Germantown Outlier (also known as the Oldwick Outlier) is the most northern of the outliers south of the Watchung Mountains. The hills of the New Germantown Outlier are located along the border of Tewksbury Township and Readington Township, New Jersey, approximately seven miles southwest of the southern extent of the Watchungs and about three miles north of Cushetunk Mountain. The structure of the New Germantown Outlier appears to mirror the construction of the Watchung Mountains on a tiny scale. The eastern side of the feature consists of a horseshoe shaped ridge with prongs facing to the west. This ridge is composed of Orange Mountain (First Watchung Mountain) basalt which is actively quarried. West of this First Watchung-like ridge is a valley occupied by sedimentary layers of the Feltville Formation, characteristic of the valley between the First and Second ridges of the Watchungs. Finally, at the center of the horseshoe is a dome of volcanic rock forming a hill known as Round Top. The hill is composed of Preakness Mountain Basalt, making it the equivalent of Second Watchung Mountain in the New Germantown complex. The thickness of basalt in this outlier is estimated at close to 425 ft (~130 m). Prospect Hill Located along the border of western Flemington and Raritan Township, New Jersey, Prospect Hill constitutes the smallest of the Watchung Outliers, being approximately one fourth of a mile wide and extending north to south for less than half a mile. The hill is composed of Orange Mountain Basalt, with no overlying Jurassic sediments apparent. Dikes branching south from the vicinity of the outlier appear to be connected to the intrusive igneous Sourland Mountain, an extension of the Palisades