We studied two short, high-gradient river systems draining the Dolomite Alps in northeastern Italy in order to determine which grain types survive transport and to what extent sand grain types reflect source rocks. Grains of all the labile rock types in the source areas survived to lower reaches of the rivers. In one drainage (Boite-Piave), they reached the Adriatic coast. Carbonate grains (largely dolomite) in the Gadera-Rienza Rivers decreased abruptly, largely by dilution, from >50% to trace amounts in 100 km of travel. Percentage of carbonate grains in the lower reaches of these rivers was generally less than one-half the areal percentage of limestone and dolostone exposure in the source areas. However, in the Boite-Piave Rivers (200 km long), enrichment of carbonate grains in beach sand at the expense of polycrystalline quartz and volcanic rock fragments results in dolostone sand at the beach reflecting 78% of its outcrop abundance and limestone (calcite) sand reflecting 68% of its outcrop abundance. Polycrystalline quartz and mafic volcanic rock fragments are less abundant in the beach because of dilution by longshore drift or the breakdown of these grains by wave abrasion. The relative resistance of carbonate textural grain types to abrasion is micrite > spar > mixed micrite/spar. The results indicate that detritus from dominantly silicic and intermediate volcanic rocks can survive fluvial transport and at least moderate wave abrasion. Metamorphic rock fragments (mostly phyllite) in the Gadera-Rienza Rivers survived transport to the confluence with the Isarco River at Bressanone. In the Boite-Piave river system, metamorphic rock fragments survived fluvial transport to the beach plus some beach abrasion. They did so because the relatively rapid transport down the high-gradient, low-sinuosity streams did not permit extensive chemical weathering. Grains of calcite (micrite and spar), dolomite, and volcanic rock fragments increased in roundness by abrasion in the surf after undergoing only a few kilometers of transport along the coast.

We studied the composition and roundness of medium sand from 18 small beaches of Elba Island. Six are pocket beaches less than 100 m long; the longest is 1.3 km long. The drainage basins of streams that supply the beaches are all less than 25 km 2 ; most are less than 5 km 2 . Beach sands range widely in composition owing to diverse source terrane. For the various drainage basins, comparison of the outcrop areas of the different types of bedrock with the compositions of beach sand grains yields the following conclusions: (1) the relative area of granodiorite outcrop is accurately represented by the amount of quartz + feldspar + quartzofeldspathic rock fragments in all beaches, although plagioclase in beach sand is significantly reduced relative to K-feldspar; (2) the relative areas of outcrop of ophiolitic and limestone bedrock are accurately represented by beach sand in pocket beaches, but are only moderately represented (ophiolitic rocks) or poorly represented (limestone) in other beaches; (3) the relative area of outcrop of metamorphic rocks is poorly represented in beach sand (metamorphic rock fragments + polycrystalline quartz) except in one anomalous beach supplied in part by mine tailings; (4) the relative area of bedded chert outcrop is poorly represented in beach sand because bedded chert does not break down into sand-size grains; and (5) shale bedrock is not represented or is only marginally represented in beach sand. For Elba beaches in general, the order of increasing roundness of grains, and thus increasing rate of abrasion, is: quartz < plagioclase < K-feldspar and igneous rock fragments (quartzo-feldspathic) < serpentine < metamorphic rock fragments < carbonate rock fragments (CRFs). There are no significant differences in roundness with beach length for quartz, K-feldspar, or CRFs. There are also no significant differences in roundness for the same three grain types from beaches of different size drainage basins, which indicates there is no perceptible rounding of grains by streams. First-cycle monocrystalline quartz grains of medium sand are unrounded, although coarser grains show minor blunting of edges. The roundness of quartz, K-feldspar, and CRFs are all greater on the eastern, more protected part of the island. This reflects a significant proportion of recycled quartz and K-feldspar in the eastern beaches, but CRFs may undergo more rounding in beaches of low to moderate wave activity than in high-energy beaches.

Abstract Paleozoic rocks that were deposited along the southeastern margin of North America during Paleozoic time and that make up the Ouachita orogen extend from Arkansas across Oklahoma and Texas and have been traced almost to Mexico. Rocks at the southwestern end of the Ouachita orogen are exposed only in the Marathon and Solitario uplifts in west Texas, but the western edge of the sequence in the subsurface of Texas is fairly well known from well and seismic data (e.g., Flawn and others, 1961; Nicholas and Rozendal, 1975). The Marathon uplift is a broad domal uplift of early Tertiary age and is more than 125 km in diameter (King, 1937). Erosion of Cretaceous and younger strata from the crest of the uplift produced the topographic Marathon Basin in which are exposed, in an area approximately 50 by 75 km, deformed Paleozoic rocks that have a composite stratigraphic thickness of 5000 m. Permian strata in the Glass Mountains unconformably overlie older rocks alongthe northwestern edge of the Marathon uplift (Fig. 1). The Solitario uplift, 65 km to the southwest, provides exposures of Paleozoic rock approximately 8 by 15 km at the crest of a buried intrusion.