Subcircular to broadly elliptical sedimentary basins of cratonic interiors remain among the more enigmatic elements of continental geology. Such basins may be characterized by significant, preserved sediment thicknesses (approaching 4 km); long subsidence history (> 100 × 10⁶ year); non-systematic but, commonly, globally synchronous variation in subsidence rates; and obscure relation to anomalies of the magnetic or gravity fields or of crustal thickness. Mechanisms involving thermal contraction and/or loading of the crust appear inadequate to explain subsidence history and amplitude. Lacking new, critical data, progress toward rational concepts is slow.

Deep drilling of basement rocks of sedimentary basins, including adequate sample recovery and measurement of thermal, magnetic, density, and stress parameters, holds the exciting promise of providing essential information for testing concepts. It is held, for example, that basins lie along ancient continental margins or at the triple junction of sutures. Remanent magnetism and petrologic and structural data from oriented cores could be definitive.

The basement rocks of the continent hold the keys to many fundamental earth science problems. The early history of the planet, the mechanisms of continental development, the nature and timing of pre-Mesozoic global tectonics, and the sources of many materials essential to society, are examples. The drill can probe the third dimension of the basement, interpolate through cover between surface exposures, extend basement data to outer continental margins, and target critical features. Measurements of the dynamic state of the crystalline crust can provide insights to seismic hazards, geothermal energy potential, hydrothermal ore-forming processes, and possible suitable settings for long-term toxic waste disposal.

A feasible basement drilling program, integrated with appropriate surface studies designed to achieve maximum scientific yield, can probe one of the great frontiers in the earth sciences.

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