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Vertical grain size progressions of sand deposits in the Queen City Formation (Eocene), East Texas, were studied to determine if unique textural trends characterize depositional environments. Results from this study indicate that certain groups of environments are more easily distinguished from other groups. Lower point bar, fluvial distributary channel, and distributary mouth bar deposits are more readily differentiated from distal bar, lower shoreface, and upper point bar deposits by the presence of a coarser mean grain size and mode, higher sand content, and more saltation modes with little suspension component. The overlap in grain size traits among many of the environments is attributed to the restricted grain size range of the formation, similarities in transport mechanisms among environments, and, to a lesser degree, diagenetic changes in the original grain size distributions. (Abstract shortened with permission of author.)

Piston cores from the western Ross Sea reveal a stratigraphy consisting of basal tills overlain by glacial-marine sediments, succeeded seaward by glacial-marine deposits with abundant microfossils and IRD. The glacigenic sediments are succeeded at the shelf margin by coarse bioclastic sands and gravels. Seismic and core data indicate that the grounding line for the late Wisconsinan glacial maximum was just north of Coulman Island. Carbonate sediments from the outer shelf were grouped into four distinct facies. Radiocarbon dates indicate that carbonate deposition was occurring during much of the late Wisconsin. The pre-mid Miocene unconformity identified in DSDP Site 273 (Hayes and Frakes, 1975) was tied to the seismic data in the western Ross Sea. The data suggests that this event was responsible for the general physiography of the western shelf. Turbidites, including calcarenites, litharenites and quartz arenites, were recovered from the slope and the data suggests that outer shelf banks are the source for these deposits.

The pre-Tertiary rocks of the Pueblo Mountains are a series of volcanic and volcanogenic rocks intruded by Middle Jurassic and possibly younger plutons. The entire sequence has undergone sub-greenschist to greenschist facies metamorphism. The Pueblo Mountains can be divided into two zones: (1) a northeast-trending, southeast-dipping shear zone in the southeast; and (2) an undeformed zone in the northwest. Three phases of deformation are associated with and restricted to the shear zone, and all show top-to-the-NW sense of shear. $\sp{40}$Ar/$\sp{39}$Ar geochronology for biotite from within the shear zone produces a minimum age for D$\sb1$ of 95 Ma. The Pueblo Mountains shear zone may be related to a similar middle Cretaceous structure in the northern Pine Forest Range, and is also similar to structures developed during and after the poorly understood suturing of the Blue Mountains province to the North American craton.

The Villa de Cura belt, one of several allochthonous belts comprising the Caribbean Mountain System of northern Venezuela, contains island arc volcanic and volcaniclastic rocks, metacherts, and mafic rocks metamorphosed to blueschist facies. It consists of four east-west trending metamorphic zones. The prograde pressure-temperature (P-T) path for the northern three zones indicates high P-low T metamorphism, with a similar retrograde P-T path. The southernmost zone formed at similar P, but higher T, and underwent a counter-clockwise P-T path. Ductile D$\sb1$ structures in the Villa de Cura belt indicate that the belt formed in a right-oblique subduction zone to the west of its present location. $\sp{40}$Ar/$\sp{39}$A, data (97 to 78 Ma) suggest that exhumation occurred in the late Cretaceous. D$\sb2$ structures are related to SSE emplacement of the belt onto South America.