Contour mapping of relic structures in the Precambrian basement of the Reelfoot rift, North American midcontinent

Rirchard L. Dart; Henri S. Swolfs

doi:10.1029/97tc03551

Home/Archive/USGS

USGS · 70021128

Contour mapping of relic structures in the Precambrian basement of the Reelfoot rift, North American midcontinent

Rirchard L. Dart·Henri S. Swolfs

View original source ↗Export metadata ↓

Abstract

A new contour map of the basement of the Reelfoot rift constructed from drill hole and seismic reflection data shows the general surface configuration as well as several major and minor structural features. The major features are two asymmetric intrarift basins, bounded by three structural highs, and the rift margins. The basins are oriented normal to the northeast trend of the rift. Two of the highs appear to be ridges of undetermined width that extend across the rift. The third high is an isolated dome or platform located between the basins. The minor features are three linear structures of low relief oriented subparallel to the trend of the rift. Two of these, located within the rift basins, may divide the rift basins into paired subbasins. These mapped features may be the remnants of initial extensional rifting, half graben faulting, and basement subsidence. The rift basins are interpreted as having formed as opposing half graben, and the structural highs are interpreted as having formed as associated accommodation zones. Some of these features appear to be reactivated seismogenic structures within the modem midcontinent compressional stress regime. A detailed knowledge of the geometries of the Reelfoot rift's basement features, therefore, is essential when evaluating their seismic risk potential.

Explore related subjects

Tectonics Article

Source-reported bounding extent: 30.023982075499177° to 40.18869293464397° latitude; -98.86776387187194° to -74.84249273915621° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Rirchard L. Dart, Henri S. Swolfs. 1998. Contour mapping of relic structures in the Precambrian basement of the Reelfoot rift, North American midcontinent. https://doi.org/10.1029/97tc03551

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Ductile and brittle Rio Grande Rift deformation in Oligocene granite records a two-stage rift history in southern Colorado

The timing and nature of early deformation in the Rio Grande Rift remains poorly constrained. We present evidence for the earliest structural signature of rift extension in the Sangre de Cristo Range, southern Colorado, based on new geologic mapping, structural analysis, rock magnetic data, and thermochronology. These analyses focus on the ~30.0 Ma granite of Chokecherry Canyon, which hosts discrete low-angle mylonitic shear zones and a distributed, gently SW-dipping protomylonitic fabric. Incremental stretching axes, stretching lineations, and Kmax magnetic lineations plunge gently WSW. Quartz microstructures and crystallographic orientations indicate dominantly coaxial strain in the protomylonite and general shear in the discrete shear zones. Quartz c-axis opening-angle thermometry suggests deformation at ~420–540°C. Thermal modeling of ⁴⁰Ar/³⁹Ar K-feldspar data indicates rapid post magmatic cooling below the brittle–plastic transition, supporting shear-zone formation immediately after emplacement. Slow cooling from ~20–13 Ma was followed by renewed rapid cooling at ~13 Ma, interpreted as the onset of extensional exhumation along the Sangre de Cristo Fault System. These results show that extension in the northern Rio Grande Rift was active by ~30 Ma, earlier than previously recognized. We propose a two-stage model for northern Rio Grande Rift evolution: Stage I (30–23 Ma) records ENE–WSW extension localized in low-angle mylonitic shear zones associated with mid-crustal intrusions; Stage II (≤18 Ma) reflects brittle high-angle normal faulting, focused exhumation, and rift narrowing. Stage I magmatism and deformation along the western range front likely established crustal weaknesses that guided later fault development.

Colorado↗

USGS2026

Exhumation history of the Sangre de Cristo Range, Colorado, from mid- to low-temperature thermochronology: New insights into Laramide contraction and Oligocene–Miocene extension in the northern Rio Grande rift, USA

The Sangre de Cristo Range in southern Colorado records a complex tectonic history that includes Late Cretaceous–Eocene Laramide contraction and Oligocene–Quaternary Rio Grande rift extension. We present new thermochronologic data ( 40 Ar/ 39 Ar, fission-track, (U-Th)/He) and thermal history models that provide insight into this polyphase history and spatiotemporal patterns of extensional exhumation. Our data indicate that the Alvarado fault, which bounds the northeastern flank of the range, initiated as a NE-dipping reverse fault during the early stages of the Laramide orogeny and was subsequently reactivated as a normal fault in the early Miocene. The onset timing of rapid cooling associated with extensional exhumation systematically youngs southwestward across the range from 20–16 Ma along the northeastern flank, 18–14 Ma near the range crest, and 14–10 Ma along the southwestern flank. We attribute this exhumation pattern to earlier onset of normal slip on the Alvarado fault, with extension shifting to the SW-dipping Sangre de Cristo fault system along the southwestern flank of the range and adjacent San Luis Basin at 14–10 Ma. The southwestern flank of the range was exhumed from temperatures of ∼240 ± 25°C at the onset of Miocene rapid cooling, consistent with ∼7–9 km of displacement across the Sangre de Cristo fault system. Thermal history models indicate limited cooling between the Oligocene inception of rift extension and the Miocene onset of rapid cooling, suggesting that development of rift flank topography and adjacent extensional basins was primarily associated with Miocene normal faulting.

Colorado↗

USGS2026

The geologic history of the Chehalis Forearc Basin, Washington State, USA

The Chehalis basin is located between the Cascade arc and the Coast Range in southwest Washington State. It consists of sedimentary and volcanic rocks deposited throughout the Cenozoic and is underlain by the Siletzia terrane, a thick, large igneous province accreted in the Eocene. Here, we constrain evolution of the Chehalis basin depocenter using isochore maps derived from isostatic gravity anomalies, borehole data, and stratigraphy for several time periods: the Eocene (47.6–36.8 Ma), the Oligocene (36.8–20 Ma), and the Neogene (20–0 Ma). Our results suggest that local subsidence is driven by deformation on faults that bound and intersect the basin. We see northward depocenter migration, interpreted as a shift in deformation from the northwest striking Cedar Creek fault to the west striking Doty fault. We interpret these data in terms of the long-term north-south shortening and clockwise rotation of the Cascadia forearc. During the Eocene, the Cedar Creek fault was preferentially aligned with north-south shortening, but became less active when clockwise rotation brought the Doty fault into east-west alignment with the stress field. Sediment accumulation rates decreased from 196 m/Myr in the Paleogene (∼40–20 Ma) to 27 m/Myr in the Neogene (∼20–0 Ma) as Miocene uplift of the Coast Range limited accommodation space and shifted the depositional environment from marine to fluvial. Our results are consistent with the geologic evolution of the Portland and Tualatin basins to the south and reveal a depositional and structural history uniquely shaped by clockwise rotation of the Cascadia forearc.

Washington↗