Silurian elastic rocks in the area of this study are the Tuscarora Sandstone, Rose Hill Formation, and Eagle Rock Sandstone in southeastern sections and Mifflintown Formation in northwestern sections. Only the Rose Hill Formation and Eagle Rock Sandstone were studied extensively. In addition, the two basal members of the Mifflintown Formation, the Lower Dolomitic Member to the west and the Keefer Sandstone Member to the east, were studied. The Rose Hill Formation is an olive or gray shale interbedded with quartz-rich siltstones and fine-grained sandstones. Hematite-cemented, medium-grained quartz sandstones are common, generally as upper and lower hematitic members. Dolomitic sandstones and shales are rare. The Eagle Rock Sandstone is dominantly a silica-cemented, fine-grained sandstone with few interbeds of gray shale. Some vertically burrowed red beds occur in southeastern localities. This is a newly defined unit that takes the place of the "Keefer" Sandstone of southwestern Virginia and intertongues with the Mifflintown Formation containing the true Keefer Sandstone Member of Maryland and Pennsylvania. The basal members of the Mifflintown Formation which were studied occur in two facies. The eastern facies (Keefer Member) is a buff, silica-cemented, fine- to medium-grained, well-sorted quartz sandstone. The western facies (Lower Dolomitic Member) is a dolomite or sandy dolomite. containing a thin bed of hematite iron ore. The Rose Hill Formation is thinner and sandier in southeastern sections than in northwestern sections where the dominant shales are fossiliferous. The hematitic members thin to the northwest where the upper member pinches out. The Eagle Rock Sandstone is thickest in southeastern sections and disappears by facies change into the Mifflintown Formation in the same area as the pinch-out of the upper hematitic member of the Rose Hill Formation. The Eagle Rock Sandstone is generally in three distinct sandstone units separated by two argillaceous units in its western exposures. A study of the conodonts from carbonates overlying the Eagle Rock Sandstone shows that it contains beds at least as young as upper Wills Creek and in some sections as young as upper Tonoloway of the Wills Mountain anticline. The brachiopod Eocoelia, supported by ostracode data, enables the establishment of a time line at approximately the C₅-C₆ time boundary which occurs near the middle of the Rose Hill Formation. The Silurian elastic units studied are in a symmetrical vertical sequence with beach deposits at the top and bottom, and marine deposits in the middle. These are interpreted as an onlap-offlap sequence of a deltaic complex (called the Giles delta) with the progradation of the delta beginning at about the time of the C₅-C₆ time boundary. The upper Tuscarora Sandstone is interpreted to be a coastal fluvial system deposit reworked by shoreline processes into a beach deposit. The lowermost Rose Hill shales are the protected nearshore deposits behind the offshore bars of the lower hematitic member of the Rose Hill Formation. The middle Rose Hill fossiliferous shales are interpreted to be the normal marine deposits west of the offshore bars. As the onlap changed to offlap at the onset of the deltaic progradation, the offshore bars (upper hematitic member) migrated westward followed by the protected nearshore muds and silts of the uppermost Rose Hill Formation, and the delta-top sands of the Eagle Rock Sandstone. / Ph. D.