Source rock texture versus climate and topography as controls on the composition of modern, plutoniclastic sand

Abstract

The rock fragment content (measured by log of polycrystalline/monocrystalline sand grains) of sand derived from five nearly identical granodiorite plutons, located in strongly contrasting climatic zones of the United States and Mexico, shows a much stronger correlation with source rock texture than with any environmental factor or combination of factors. These factors include mean annual temperature (range, -4° to 28°C), mean annual precipitation range (range, 201 to 1,566 mm), mean annual surplus of precipitation over évapotranspiration (range, 0 to 1,138 mm), average drainage slope (range, 0.29 to 0.61), or relief ratio (range, 0.17 to 0.70). Source rock texture is measured by intercrystalline area/volume of source rock and has a range of 7.99 to 25.08 mm -1 . Stepwise regression analysis indicates that, in coarse sand, 71% of variation in rock fragment content is accounted for by variations in source rock texture versus 16% accounted for by variations in temperature. In medium sand, 96% of the variation in rock fragment content can be attributed to texture versus 1% for slope and <1% for temperature. In fine sand, 92% of the variation in rock fragment content stems from texture versus 3% from temperature. The same analysis does not document a statistically significant relationship between precipitation and rock fragment abundance. Many previous studies that appear to document a relationship between rock fragment abundance and precipitation in modern and ancient sand have not accounted for variations in source rock lithology that are more plausible explanations for observed variations in rock fragment abundance in derived sand.

Composition of modern stream sand derived from a mixture of sedimentary and metamorphic source rocks (Henares River, Central Spain)

“…McBride and Picard, 1987;Heins, 1993;Palomares and Arribas, 1993). Quantitative analysis of mixing relationships between two different source rocks depends on whether both rock types generate clear diagnostic detrital grains (Molinaroli and Basu, 1993 Bomova and Sorbe rivers are good examples of mixed deposits from a variety of source rocks.…”

Holocene transgression recorded by sand composition in the mesotidal Galician coastline (NW Spain)

“…In contrast, sands from Traba have greater proportions of the undulose variety (Qmo). The predominance of mono crystalline typologies can be related to their origin, associated with coarse-grained plutonites, mainly granitoids (Basu et al, 1975;Tortosa, 1988;Tortosa et al, 1991;Heins, 1993). Differences between undulose and non-undulose types may suggest differences in deformation of the original source rock (e.g.…”

Influence of granitoid textural parameters on sediment composition: Implications for sediment generation

“…Whitmore et al, 2004;Garzanti et al, 2009). Heins (1993Heins ( , 1995 provided a wealth of information on framework composition of modern felsic plutoniclastic sands derived from granitoid plutons of the Cordilleras of the United States and Mexico. These studies demonstrated that the textural parameters of parent rocks represent the main control on rock-fragment abundance in modern plutoniclastic sand (Heins, 1993), and that the types of mineral interfaces preserved in rock fragments are closely related to climate and topography of the source area (Heins, 1995).…”

“…The climatic signature is preserved in the sandy detritus if it does not suffer sedimentary differentiation during longdistance transport and deposition in high-energy littoral environments or exceptionally deep burial diagenesis (Suttner and Dutta, 1986). Studies of Holocene sands may provide actualistic compositional data to serve as a basis for inferring paleoclimate from ancient sandstones (e.g., Young et al, 1975;Basu, 1976;James et al, 1981;Franzinelli and Potter, 1983;Grantham and Velbel, 1988;Girty, 1991;Heins, 1993Heins, ,1995Weltje et al, 1998;Le Pera et al, 2001).…”

“…Heins (1993Heins ( , 1995 provided a wealth of information on framework composition of modern felsic plutoniclastic sands derived from granitoid plutons of the Cordilleras of the United States and Mexico. These studies demonstrated that the textural parameters of parent rocks represent the main control on rock-fragment abundance in modern plutoniclastic sand (Heins, 1993), and that the types of mineral interfaces preserved in rock fragments are closely related to climate and topography of the source area (Heins, 1995). Palomares and Arribas (1993) introduced the Sand Generation Index (SGI) for granitic and metamorphic terrains in the Spanish Central System as a method for quantifying the capacity of different parent rocks to produce sand-sized detritus.…”