PdS receiver function evidence for crustal scale thrusting, relic subduction, and mafic underplating in the Trans-Hudson Orogen and Yavapai province

Abstract

The Trans-Hudson Orogen (THO) in the north central United States represents a major suturing event between the Wyoming and Superior Archean provinces. It is bounded to the south by the NE-SW striking Yavapai province, which was accreted along the southeastern margin of North America between 1.71 and 1.68 Ga and was one of a series of major collisional events responsible for the assembly of Laurentia. In this study, PdS teleseismic receiver functions were used to investigate the deep crustal structure associated with these collisions. Using data from over 800 broadband seismic stations distributed throughout the Great Plains/Midcontinent region, we calculated 0.5 Hz receiver functions using 245 M > 6.0 teleseismic events. The receiver functions were then CCP (common conversion point) stacked to create a 3D image volume. Profiles through this image volume show evidence of crustal scale thrusting of the Wyoming province in the west over the Superior province in the east and a relic subduction zone associated with the Yavapai-Superior boundary. We also performed a density analysis of the region using relative amplitude of the 2p1s and 0p1s receiver function phases from 233 stations. These data indicate a relatively low Moho density contrast throughout the THO and northern Yavapai Province associated with a region of thickened crust (>50 km), which we interpret to be evidence of a dense lower crustal layer that is the result of mafic underplating.

Distinct crustal isostasy trends east and west of the Rocky Mountain Front

“…Thicker crust, ~42–53 km, underlies the Colorado Plateau, southern Rocky Mountains, the western end of the Wyoming craton‐Yavapai Province suture, and the Trans Hudson Orogen (THO). Compared to prior results the THO crust is slightly thinner, with a maximum thickness of ~53 km compared to prior estimates of up to 55–60 km [ Thurner et al, ; Shen et al, ]. Prior estimates for the western Colorado Plateau vary from ~35 to 58 km [ Levander et al, ; Wilson et al, ; Bashir et al, ; Gilbert , ], and we found a range of ~45–50 km because we interpolated across small areas where the Moho is ambiguous due to multiple weak arrivals.…”

Seismic Imaging of the North American Midcontinent Rift Using S‐to‐P Receiver Functions

“…Furthermore, in a passive rifting regime, greater degrees of lithospheric thinning are expected (Huismans & Beaumont, ), even over the short lifetime of the MCR of ~20 Myr (Vervoort et al, ). Instead, we image negative velocity discontinuities in the mantle lithosphere that likely predate the MCR with a lack of observed perturbations spatially related to the rift, particularly in the north‐dipping negative discontinuity (cross section E–E′; Figure ) that is likely related to Yavapai accretion (Hopper & Fischer, ; Thurner et al, ). Additionally, our constraints on an altered Moho and addition of crustal underplating over a relatively focused, small lateral area beneath the rift axis supports focused magmatism at ~60‐km depth, which is more consistent with an active component of upwelling.…”

“…The main negative phase at 90–120 ± 7‐km depth in the southern and middle segments is also north dipping. The dipping feature may be related to the relict subduction zone from the accretion of the Yavapai Province to the Superior Province ~1.7 Ga (Hopper & Fischer, ; Thurner et al, ). These are therefore likely features that predate the MCR and furthermore do not seem to exhibit rift‐related modification in what we image.…”

Teleseismic P wave spectra from USArray and implications for upper mantle attenuation and scattering

“…Both of which have been identified by scattered teleseismic P waves in many areas across the U.S. [e.g., Porter et al ., ; Wirth and Long , ; Thurner et al ., ]. The A1/A parameter from Schulte‐Pelkum and Mahan [] represents the amplitude of degree 1 back‐azimuth‐dependent signal normalized by the total signal amplitude during the first 8 s of the receiver function time series, which corresponds to scattering at depths less than about 80 km.…”