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doi:10.2204/iodp.proc.341.204.2017

Introduction

A major goal of Integrated Ocean Drilling Program (IODP) Expedition 341 Southern Alaska Margin was investigation of interrelationships between tectonic processes, paleoclimate, and glacial activity. One of the primary expedition research questions focuses on if and how large-scale mass redistribution through rapid sedimentation or glacial advance and retreat can alter the geometry of tectonic wedges in a temperate glaciated margin (e.g., Berger et al., 2008; Worthington et al., 2010). High-resolution sequence stratigraphic and structural studies of the offshore sedimentary record are essential to establishing connections between tectonic deformation and glacial processes. Developing accurate chronological relationships requires careful calibration between seismic and well-derived data. Here, we focus on core-log-seismic integration of Sites U1420 and U1421 near the Bering Trough offshore southeast Alaska. Coring at these sites (Fig. F1) sampled sediments of the Pamplona fold and thrust belt, which has accommodated shortening during Yakutat microplate convergence with North America since ~25 Ma (Worthington et al., 2010).

Constraining the rate, amount, and distribution, of sedimentation is important to evaluating regional hypotheses relating shelf development, tectonic activity, and paleoclimate variations. Well and logging data from Expedition 341 provides important stratigraphic, physical property, and age data recorded in depth which facilitates development of a constrained stratigraphic model that can be extended across the shelf if carefully integrated with local and regional seismic surveys. The challenging drilling environment resulted in limited core recovery due to large clasts and poorly consolidated material and difficult logging mostly due to borehole instability (see the “Site U1420” and “Site U1421” chapters [Jaeger et al., 2014b, 2014c]). These factors result in significant data gaps that present challenges with core-log-seismic integration. We attempt to bridge data gaps by using aggressively fitted splines in constrained intervals where data coverage did not include significant gaps greater than ~25 m. In poorly constrained intervals, with gaps as large as ~270 m, we apply spline fits with a higher smoothness parameter (Silverman, 1985). The smoother splines typically fit the data less well in constrained intervals but result in more conservative estimates of variability where measurements are lacking. We used the continuous spline curves to generate synthetic seismograms at the site and matched the synthetic traces with high-resolution seismic survey EW0408 Lines GOA 2503 and GOA 2505 according to traditional well-tie techniques (e.g., White, 1997; White and Simm, 2003). We used these time series and depth series matches to develop the final time-depth relationship (TDR) presented here that can be used to improve the calibration of developing age models. This study advances Expedition 341 scientific goals by providing a core-, log-, and seismic-constrained TDR for two sites on the southern Alaska shelf.

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