--> Latitudinal Controls on Siliciclastic Sediment Production and Transport

AAPG Annual Convention and Exhibition

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Latitudinal Controls on Siliciclastic Sediment Production and Transport

Abstract

How latitude influences climate and the complexities therein, and the production and transport of siliciclastic sediment, will be explored. The primary latitudinal influence is on temperature, precipitation, wind and wave patterns. Surface radiation directly also influences river-water density. At any given latitude, a wide range of precipitation intensities exist, ranging from arid to wet conditions. Precipitation is influenced by the dynamics of atmospheric, but is also strongly modified by land-sea interactions and land surface topography. Global wind patterns are strongly influenced by atmospheric circulation dynamics that form the zonal wind belts. Strong winds include those associated with fronts between air masses and pressure systems and as influenced by topography, short-lived convective winds under thunderstorms, and winds associated with tropical cyclones. Maximum wave power is found on temperate and subarctic western coastlines. Swell-dominated coastlines are located in the tropical western coastlines. Eastern continental coastlines recieve lower wave energy. Arctic Ocean waves are fetch-limited. Secondary latitudinal influences include climatic impacts on sediment production. A water temperature increase of 1 °C causes a ∼3.1% decrease in the suspended sand transport — suspended sand concentration decreases by ∼2%, suspended silt and clay concentration drops off by only 0.35%, flow velocity decreases by ∼0.66%, and there is ∼2.2% rise in the von Karman parameter. While the abundance of fine sedimentary particles in transport might reflect biochemical weathering of source rocks and soils, intensified downstream fining might also reflect the decreasing transport competency associated with increased water temperature and reduced kinematic viscosity. Scaling models allow for a hypothetical polar river, to be compared to an equally sized river draining similar topography, but as influenced by another climate. Polar climates yield less sediment: 1) melt-induced runoff yield smaller flood waves then surface runoff from falling rain; 2) frozen soils and river beds reduce sediment yield; and 3) summer-time polar rain falls is less intense than from temperate or tropical regions. A basin having similar drainage area and relief, and lithology will have 25 times sediment transport when compared to a tropical basin. Arid basins produce less sediment and more of this sediment is stored between the source area and the coast.