Abstract: The Ramseyburg middle graywacke member of the Middle to Upper Ordovician Martinsburg Formation of Pennsylvania and New Jersey was analyzed petrologically in order to identify its provenances, with a view toward reconstructing the basinal and source-area evolution in a plate tectonic context. A total of 48 samples were studied, taken from seven localities along the Martinsburg outcrop belt,which extends for 220 km. These samples were analyzed for the following detrital grains: monocrystallinequartz, polycrystalline quartz, volcanic and sedimentary lithic fragments, plagioclase, and potassiumfeldspar. On each thin section, 500 points have been counted for these grains and been placed in triangular modal diagrams. Analytic data obtained from 200 basins which are formed by different tectonicregimes are represented by various parts of triangles. Therefore the relationship betwen tectonics andsandstone petrology are set up directly.Analyzed data reveal that the Martinsburg turbidites had two provenances: a more dominant recycled orogenic and a subordinate cratonic interior. The southwestern portion of the basin was dominantly fed by reworked Late Cambrian/Early Ordovician sedimentary cover, and the northeastern partof the basin received its elastics from granitic and gneissic plutons of the North American basementthat were exposed after the sedimentary cover was eroded. The rarity of predominantly basaltic detritusin the Martinsburg graywackes indicates that the arc provenance was not the prime source for thesesediments.The evolution of the Martinsburg basin and its source areas is accounted for by a plate tectonicmodel which requires the collision of the North American craton with an island arc or microcontinent left from Precambrian rifting. This proposed tectonic model provides additional insights regarding the emplacement of the Hamburg klippe, and of pillow basalts and thin volcanic ash layers presentelsewhere along the outcrop belt at the base of the Martinsburg Formation.