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Sedimentary Basins
Brian Horton

Vibrant interest in the dynamic interplay of tectonics and climate has driven research advances in basin research, with discoveries resulting from new laboratory applications, field studies and theoretical models. Because uplift of Earth's mountain belts and continental plateaus may force changes in global climate, seawater chemistry, and the carbon cycle, understanding basins in these settings forms a vital aspect of sedimentary research.

In one such study of the Tibetan and Altiplano-Puna plateaus, Edward Sobel and colleagues integrated theoretical geomorphic models with field studies to identify specific tectonic and climatic conditions conducive to basin development (Journal of Geophysical Research, v. 108, art. no. 2344). They found that an arid climate and internal drainage may be necessary conditions for plateau growth.

Paleoelevation investigations of basins in the Tibetan plateau suggest attainment of the present 4-to 5-kilometer altitudes by 15 to 12 million years ago, substantially earlier than thought (Spicer et al., Nature, v. 421, p. 622; Dettman et al., Earth and Planetary Science Letters, v. 214, p. 267). These studies utilize leaf physiognomy of preserved fossil plants and oxygen stable-isotope records of lake carbonates as proxies for ancient temperature and altitude.

Additional basin research in Asia has applied magnetostratigraphy to date initial shortening induced by the India-Asia collision in China (Fang et al., Earth and Planetary Science Letters, v. 210, p. 545; Pares et al., Journal of Geophysical Research, v. 108, art. no. 2017) and has shown the complexity and tremendous regional extent of Mesozoic extension in eastern Asia (Meng et al., Basin Research, v. 15, p. 397)

In terms of technical advances, more sophisticated applications of detrital minerals and dating techniques yielded new insights into the rates of denudation and accumulation. Using a variety of isotopic dating techniques and fission-track analyses of detrital minerals from modern and ancient basin fill, several projects have implemented new sampling strategies and modeling techniques to help determine the complexity of detrital provenance and to quantify the timing and tempo of orogenic exhumation. Although high rates of denudation and sediment flux in the Himalayas may come as no surprise (see Syvitski et al., Sedimentary Geology, v. 162, p. 5, for a global summary of sediment flux), the highest rates of Quaternary denudation need not correlate with the zones of highest modern precipitation (Burbank et al., Nature, v. 426, p. 652).

A new dating technique based on lead-210 activity has quantified annual and decadal variations in sedimentation in the Amazonian foreland basin. Rolf Aalto and colleagues (Nature, v. 425, p. 493) discovered that floodplain accumulation is discontinuous over decadal scales and that increased accumulation rates correlate systematically with precipitation events in the El Niño/Southern Oscillation cycle over the past century (Geotimes, December 2003).

In the Andes, controversy persists over the timing and dynamics of basin development during initial mountain building, an issue fundamental to the application of sedimentary geology to tectonic problems. Elías Gómez and colleagues (Geological Society of America Bulletin, v. 115, p. 58, p. 131) and Peter DeCelles and myself (Ibid., p. 58) document basin sedimentation synchronous with Eocene-Oligocene shortening in the northern Andes of Colombia and central Andes of Bolivia. However, Federico Dávila and Ricardo Astini report Neogene extension in the southern central Andes of western Argentina (Basin Research, v. 15, p. 379).

The next generation of quantitative sedimentary basin modeling has arrived in the form of finite-element techniques (Garcia-Castellanos et al., Journal of Geophysical Research, v. 108, art. no. 2347) and numerical techniques (Clevis et al., Sedimentary Geology, v. 163, p. 85) that combine the wide-ranging effects of climate, tectonics, sea level, subsidence and drainage network configuration. These models, in combination with experimental basins, should help answer fundamental questions regarding the controls on global sea-level variations and the driving mechanisms of regional gravel transport (Heller et al., Geological Society of America Bulletin, v. 115, p. 1122). As the models improve, the need continues to grow for more accurate data sets collected from detailed studies of modern and ancient basins from diverse tectonic and climatic regimes.

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Horton is an assistant professor in the Department of Earth and Space Sciences at the University of California, Los Angeles. E-mail: horton@ess.ucla.edu.

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