Abstract

Framework modes of terrigenous sandstones reflect derivation from various types of provenance terranes that depend upon plate-tectonic setting. Triangular QFL and QmFLt compositional diagrams for plotting point counts of sandstones can be subdivided into fields that are characteristic of sandstone suites derived from the different kinds of provenance terranes controlled by plate tectonics. Three main classes of provenance are termed “continental blocks,” “magmatic arcs,” and “recycled orogens.” Sandstone suites from each include three variants, of which the subfields lie within the larger subdivisions. Average modes for sandstone suites can be classified provisionally according to tectonic setting using the subdivided QFL and QmFLt plots.

To test the validity of the classification, average modes for 233 Phanerozoic sandstone suites from North America were plotted on the triangular compositional diagrams and accompanying paleotectonic maps. Paired maps and ternary diagrams were prepared for eight different time slices, for each of which the tectonic setting of each major region within the continent remained relatively unchanged. Time slices are unequal in length but are controlled by the timing of major orogenic and rifting events that affected North America during the Phanerozoic. Comparison of the sandstone compositions with inferred tectonic setting through the Phanerozoic indicates that the proposed classification scheme is generally valid and yields satisfactory results when applied on a broad scale. Its application, together with other approaches, in regions of the world where over-all trends of geologic history are less well known could lead to important conclusions about the timing and nature of major tectonic events.

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