In the past decades the relationship between plate tectonics and sand (sandstone) composition has been one of the leading topics in sedimentary petrology. Thanks to Dickinson & Suczek (1979), Ingersoll & Suczek (1979), Valloni & Mezzadri (1984), Valloni (1985) and others, valid schemes for interpreting plate tectonics from detrital modes of sand and sandstones have been provided. Among the variety of schemes proposed in literature, those of Dickinson & Suczek and Ingersoll & Suczek are probably the most successful; the use of their work has been a routine procedure for many authors dealing with ancient plate tectonic recognition. Such a routine use may, however, be inappropriate. Recently, Lash (1987) carried out provenance studies from detrital modes from three coeval petro-facies of the Middle Ordovician sandstones of the Greenwich slice (Pennsylvania). This study is wel¬comed for increasing the available data on the petrography of sandstones from trench deposits and for highlighting the possible supply from various sediment sources. Lash plotted his point-count results on three triangular diagrams on the basis of primary petrographic parameters Q-F-L (fig. 2) and secondary petrographic parameters Qp-Lvm-Lsm (fig. 3A) and Lm-Lv-Ls (fig. 3B). The categories of detrital grains counted, and the compositional parameters, are those described and recommended by Ingersoll & Suczek (1979), though with the addition of carbonate lithic fragments which were included in the Ls and L grain populations. Then, a comparison between the author's plots and the diagrams proposed by Dickinson & Suczek (1979) and Ingersoll & Suczek (1979) were made in order to infer plate tectonic provenance of the Greenwich slice sandstones (figs 2 and 4).
Longitudinal petrographic variations in a Middle Ordovician trench deposit, central Appalachian Orogen: A Discussion
SACCANI, Emilio
1988
Abstract
In the past decades the relationship between plate tectonics and sand (sandstone) composition has been one of the leading topics in sedimentary petrology. Thanks to Dickinson & Suczek (1979), Ingersoll & Suczek (1979), Valloni & Mezzadri (1984), Valloni (1985) and others, valid schemes for interpreting plate tectonics from detrital modes of sand and sandstones have been provided. Among the variety of schemes proposed in literature, those of Dickinson & Suczek and Ingersoll & Suczek are probably the most successful; the use of their work has been a routine procedure for many authors dealing with ancient plate tectonic recognition. Such a routine use may, however, be inappropriate. Recently, Lash (1987) carried out provenance studies from detrital modes from three coeval petro-facies of the Middle Ordovician sandstones of the Greenwich slice (Pennsylvania). This study is wel¬comed for increasing the available data on the petrography of sandstones from trench deposits and for highlighting the possible supply from various sediment sources. Lash plotted his point-count results on three triangular diagrams on the basis of primary petrographic parameters Q-F-L (fig. 2) and secondary petrographic parameters Qp-Lvm-Lsm (fig. 3A) and Lm-Lv-Ls (fig. 3B). The categories of detrital grains counted, and the compositional parameters, are those described and recommended by Ingersoll & Suczek (1979), though with the addition of carbonate lithic fragments which were included in the Ls and L grain populations. Then, a comparison between the author's plots and the diagrams proposed by Dickinson & Suczek (1979) and Ingersoll & Suczek (1979) were made in order to infer plate tectonic provenance of the Greenwich slice sandstones (figs 2 and 4).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
