An Integrated Analysis of an Ancient Plate Boundary in the Rocky Mountains

An Integrated Analysis of an Ancient Plate Boundary in the Rocky Mountains, Figure 1 Figure 1.

Index map of the CD-ROM seismic experiments. The controlled source seismic stations (green), their corresponding shotpoints (red stars), and the northern and southern passive arrays (light blue diamonds) are shown. Yellow dots indicate the locations of gravity stations. The Deep Probe experiment profile that also used the Day Loma shotpoint is shown as a white dashed line.
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Integration of multiple data sets to obtain better resolved, multiple parameter earth models has recently received new emphasis. We conducted an integrated analysis of the controlled-source seismic (CSS) and passive source seismic data from the CD-ROM (Continental Dynamics of the Rocky Mountains) experiment along with gravity and seismic reflection data. A specific goal of this study was establish a stronger tie between the CD-ROM and Deep Probe experiments that together form a profile that extends from northern New Mexico to Alberta, Canada. A major advantage of the CD-ROM seismic experiment dataset was the coincidence of the seismic profiles (Fig. 1), which facilitated a joint interpretation of our new results and the previous CD-ROM results. As the first step in this process, we created a new P-wave velocity and interface model from the CSS data based on an advanced picking strategy that produced a new and extended set of travel-time picks relative to those employed in previous studies. In addition, we were able to identify a substantial set of S-wave arrivals and establish an independent S-wave model. Thus, we were able to compare and jointly interpret crustal thicknesses the various techniques produced as well as vp/ vs ratios from receiver functions and the CSS dataset. Furthermore, the comparisons provided insights about the strengths and uncertainties of each technique. Thanks to the integration of the controlled-source and receiver function results, we were able to construct a well-constrained structural model and tectonic interpretation that shows the structural framework of the transition from the Wyoming craton to the north across the suture Cheyenne belt suture zone into the Proterozoic terranes to the south (Fig. 2). The interpretation that crustal-scale crocodile structures are present provides an explanation for the south dip of the Cheyenne belt suture in the upper crust and the north-dipping slab in the mantle (Fig. 2). The very distinct crustal structures north and south of the suture zone are clearly shown in our model and document that the blocks that collided ~1.8 Ga to form the Cheyenne belt suture zone have retained their basic crustal and uppermost mantle structure since that time.
</p><p>Acknowledgements: This work was supported by the National Science Foundation as part of the GEON project (EAR-0225670)</p>

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