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Receiver function and gravity constraints on crustal structure and vertical movements of the Upper Mississippi Embayment and Ozark Uplift
Author(s) -
Liu Lin,
Gao Stephen S.,
Liu Kelly H.,
Mickus Kevin
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2017jb014201
Subject(s) - geology , precambrian , bouguer anomaly , receiver function , crust , subsidence , mafic , seismology , plume , geothermal gradient , gravity anomaly , petrology , geophysics , geomorphology , tectonics , geochemistry , paleontology , lithosphere , structural basin , physics , oil field , thermodynamics
The Upper Mississippi Embayment (UME), where the seismically active New Madrid Seismic Zone resides, experienced two phases of subsidence commencing in the Late Precambrian and Cretaceous, respectively. To provide new constraints on models proposed for the mechanisms responsible for the subsidence, we computed and stacked P ‐to‐ S receiver functions recorded by 49 USArray and other seismic stations located in the UME and the adjacent Ozark Uplift and modeled Bouguer gravity anomaly data. The inferred thickness, density, and V p / V s of the upper and lower crustal layers suggest that the UME is characterized by a mafic and high‐density upper crustal layer of ∼30 km thickness, which is underlain by a higher‐density lower crustal layer of up to ∼15 km. Those measurements, in the background of previously published geological observations on the subsidence and uplift history of the UME, are in agreement with the model that the Cretaceous subsidence, which was suggested to be preceded by an approximately 2 km uplift, was the consequence of the passage of a previously proposed thermal plume. The thermoelastic effects of the plume would have induced wide‐spread intrusion of mafic mantle material into the weak UME crust fractured by Precambrian rifting and increased its density, resulting in renewed subsidence after the thermal source was removed. In contrast, the Ozark Uplift has crustal density, thickness, and V p / V s measurements that are comparable to those observed on cratonic areas, suggesting an overall normal crust without significant modification by the proposed plume, probably owing to the relatively strong and thick lithosphere.