ABSTRACT We have identified 57 large-magnitude, sequence boundaries in the Phanerozoic succession of the Canadian High Arctic. The characteristics of the boundaries, which include angular unconformities and significant changes in depositional and tectonic regimes across the boundaries, indicate that they were primarily generated by tectonics rather than by eustasy. Boundary frequency averages 10 million years throughout the Phanerozoic and there is no notable variation in this frequency. It is interpreted that each boundary was generated during a tectonic episode that lasted two million years or less. Each episode began with uplift of the basin margins and pronounced regression. This was followed by a rapid subsidence and the flooding of the basin margins. Each tectonic episode was terminated by a return to slow, long-term subsidence related to basin forming mechanisms such as thermal decay. The tectonic episodes were separated by longer intervals of tectonic quiescence characterized by slow subsidence and basin filling. The tectonic episodes are interpreted to be the product of changes in lithospheric stress fields with uplift being related to increased, compressional horizontal stress and the following time of rapid subsidence reflecting a decrease in such stresses or an increase in tensional stresses. Conversely, the longer intervals of tectonic quiescence would reflect relatively stable, horizontal stress fields. The episodic changes in stress fields affecting the Canadian High Arctic throughout the Phanerozoic may be a product of intermittent, plate tectonic reorganizations that involved changes in the speed and directions of plate movements. The longer intervals of tectonic quiescence would occur during times of quasi-equilibrium in the plate tectonic mosaic. The tectonic episodes that generated the sequence boundaries were governed by nonlinear dynamics and chaotic behavior, and there is a one-in-10-million chance that a tectonic episode will be initiated in the Canadian High Arctic in any given year. Thus, the major transgression associated with each episode can be referred to as a “10-million-year flood.”

Abstract A new method for recognizing hydrocarbon seepage and migration in exploration wells is documented from the Immiugak A-06 exploration well that drilled through a hydrocarbon-related diagenetic zone (HRDZ). The HRDZ is seismically conspicuous as part of a gas chimney on a shale-cored anticline in the Tertiary of the Beaufort-Mackenzie Basin, Arctic Canada. The HRDZ contains classic diagenetic minerals, notably greigite (Fe 3 S 4 ) and calcite with δ 34 S and δ 13 C values diagnostic of hydrocarbon-related, sulfate-reducing, microbial activity. The HRDZ also contains exceptionally preserved calcareous benthic foraminifera with conspicuous bitumen-filled chambers and agglutinated foraminifera with bitumen and diagenetic silica with bound particles. Silica was highly mobile within the seepage or migration system and was precipitated and dissolved extensively in the agglutinated foraminifera. Seismic profiles, resistivity anomalies, diagenetic minerals, and altered foraminifera all suggest that significant hydrocarbons migrated or seeped through sandy Oligocene and Miocene strata at the crest of a shale-cored anticline in response to late Miocene tectonism. Hydrocarbon-related diagenesis can be distinguished from standard burial diagenesis using the foraminiferal coloration index (FCI). Foraminiferal coloration within the HRDZ was controlled by silicification in a bitumen-rich environment. The FCI values in the HRDZ are much higher than predicted for normal burial and show abnormal variance caused by variable dissolution of foraminiferal silica. The FCI values from agglutinated foraminifera outside the HRDZ show a uniform linear trend increasing with depth. The extent of hydrocarbon-related diagenesis observed in foraminifera can be used to assess the relative magnitude of hydrocarbon seepage in the Beaufort-Mackenzie Basin and potentially other petroleum basins.

Abstract The first section of this chapter is a review highlighting some of the important trends and developments that occurred during the past century in the application of geomorphic and stratigraphic principles and techniques in Alaska archaeology. It compliments Thorson's (this volume) review of geological problems and contexts applicable to many Alaskan archaeological sites by providing the historic context that led to contemporary application of geological principles and techniques to archaeological research in Alaska. The review is followed by a regional example used to illustrate a contemporary application of tephrochronology for the Middle Susitna River Project. From it, we see both the utility and limitations of tephrochronology for the establishment of a broad local cultural chronologic framework, and how such a framework can be used to interpret prehistory.