Wes Wallace has worked for two summers in northeastern Siberia with structural geologists of the Yakutian Institute of Geological Sciences, Russian Academy of Sciences. This is one part of a cooperative project that also includes studies of paleomagnetism (Stone), geochronology (Layer), and seismicity (Fujita and Stone), which are described elsewhere in this report.
The Chersky Range of northeastern Siberia displays a sharp bend that is convex-westward, toward the interior of the continent. This probably is partly a reflection of the shape of an originally irregular ancient continental margin against which later structures have conformed. A major objective of this study is to determine whether the arcuate trend of these later structures formed by oroclinal bending of originally straighter structures, or whether they formed in place, perhaps during multiple events with different displacement directions.
Field observations in the two limbs of the bend indicate that at least two generations of structures formed during convergence in different directions. Early northwestward convergence may reflect oblique collision of displaced continental terranes with the Siberian continental margin. Later southwestward convergence may reflect collision of Arctic Alaska with the Siberian continental margin and the terranes accreted to it. This second event resulted in the Eurasian and North American continents being sutured together in northeastern Siberia, thus separating the Arctic and Pacific Ocean basins. These observations are significant for the reconstruction of the tectonic evolution of northeastern Siberia and its relationship to the tectonic evolution of Alaska, as well as offering a possible analog for other arcuate structural trends elsewhere in the world.
ARCO Alaska, BP Exploration (Alaska), Chevron USA, Exxon Company USA,
Japan National Oil Corp., Mobil Exploration and Producing US, Phillips
Petroleum, Unocal, and Russian Academy of Sciences funds.
UAF scientific personnel:
W.K. Wallace.