An integrated analysis of controlled and passive source seismic data across an Archean‐Proterozoic suture zone in the Rocky Mountains

Abstract

[1] We conducted a new integrated analysis of the controlled and passive source seismic data from the Continental Dynamics of the Rocky Mountains (CD-ROM) experiment in the western United States. A specific goal of our study was to establish a stronger tie between the CD-ROM and Deep Probe experiments that together form a transect that extends almost 3000 km from northern New Mexico to the southern Northwest Territories of Canada. We created a new P wave velocity and interface model from the controlled source seismic (CSS) data on the basis of an advanced picking strategy that produced substantially more arrivals whose traveltimes could be picked. In addition, we were able to identify a substantial set of S wave arrivals and to establish an independent S wave model, which allowed us to estimate the Vp/Vs and Poisson's ratios in the crust. An integrated analysis of the CSS data with recently generated receiver function results and gravity data allowed us to construct a well-constrained multiparameter structural model. This model resolves the structural framework of the crust and uppermost mantle of the transition from the Wyoming craton to the north, across the Cheyenne belt suture zone, and into the Proterozoic terranes to the south. Our tectonic interpretation that crustal-scale crocodile structures are present provides an explanation for the south dip of the Cheyenne belt in the upper crust and the north dipping slab in the mantle revealed by earlier tomographic results. 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 at $1.8 Ga to form the Cheyenne belt suture zone have retained their basic crustal and uppermost mantle structure since then.Citation: Rumpfhuber, E.-M., and G. R. Keller (2009), An integrated analysis of controlled and passive source seismic data across an Archean-Proterozoic suture zone in the Rocky Mountains,

Rocky Mountain evolution: Tying Continental Dynamics of the Rocky Mountains and Deep Probe seismic experiments with receiver functions

“…Furthermore, the H-k stacking results are used in the companion paper by Rumpfhuber and Keller [2009], which is integrating these results with the outcome of the controlled-source seismic data set, and providing a tectonic synthesis of the area. However, to provide an image along the profile, we have chosen common conversion point stacking and migration techniques for further analysis, which will be discussed in further detail below.…”

Geophysical Constraints on the Flexural Subsidence of the Denver Basin

“…The second interface at 55.1 km depth on the south profile has a big uncertainty of ±6.5 km (based on the slope variation) and fits the seismic data as well. A high P-wave velocity layer is present in the lower crust at 35-55 km depth Rumpfhuber and Keller, 2009;Gilbert, 2012) Table A1) and basement structure map by .…”

“…Assuming the average upper crust density of 2.761 g/cc calculated using the velocity model by Rumpfhuber and Keller (2009) and velocity to density conversion equation (1) in Brocher (2005), the weight of the current topography across the Front Range Uplift to the west of the Denver Basin axis (a region no more than 600 km wide) is estimated to range from 3.63-4.65 x 10 13 N/m for the three profiles. This is an order of magnitude larger than the loads required to produce the flexural shape of the basin.…”

“…The initial densities used in the models were based on density log data for sedimentary units (cogcc.state.co.us: Table A1) and were derived from seismic velocities for the crystalline crust and mantle (Rumpfhuber and Keller, 2009) using Brocher's (2005) equation.…”

“…In all of the gravity models, the crust thickens abruptly at the boundary between the Rocky Mountains and Great Plains, from about 48 km beneath the Denver Basin to about 53 km beneath the Front Range Uplift. Table 2: Relationship of seismic velocities (Rumpfhuber and Keller, 2009) and densities according to Brocher (2005)………………………………………………………………….30 Table 3: Results of flexural modeling………………………………………………………..31 Table 5: Gravity model block geometry: Lithospheric mantle models………………………31 Table 6: Gravity model block geometry: Lower crust models……………………………….31 Interior Seaway and sea level conditions extending to ca. 68 Ma, followed by abrupt and episodic uplifts to the west.…”