HARTNEY STRUCTURE

by: Charles O’Dale

Type: Complex?
Age Ma: <190 ± 20 (Geological dating)^a – JURASSIC
Diameter: 6 km
Location: N 49° 23’ 42″ W 100° 39’ 26″

^a The age of Hartney appears to be Jura-Triassic, similar to Viewfield (Sawatzky 1974).

Manitoba – St. Martin, High Rock and Hartney structures. The Hartney structure is indicated by the RED dot at the lower left of the map., south west of Brandon.

The approximate 6 Km diameter Hartney structure is indicated by the red circle. It is a buried depression underlain by brecciated carbonates (Courtesy Google).

The Hartney structure from the north west taken from approximately 4000 feet above ground level. “Ground zero” is image centre.

Sawatzky H.B. Buried impact craters in the Williston Basin and adjacent area Lunar and Planetary Institute 1977

ABSTRACT:

The Hartney structure is located in southwest Manitoba (approx. 49˚N, 100˚30´W) and was discovered as a result of hydrocarbon exploration (Anderson, 1980). The structure is about 6 km in diameter. Seismic data acquired over the anomaly shows structural disruption from the Winnipeg shales (Ordovician in age) to the Lower Cretaceous Blairmore formation. Although the diameter of the structure falls within the regime for complex morphology, it appears that the center of the structure is a structural low surrounded by a ring anticline and subsequent syncline. While “peak-ring” morphologies are possible, this structure is probably too small for such development. On the other hand, near the center of the anomaly, drilling results have shown structurally uplifted Devonian strata and a complete absence of Mississippian strata (Anderson, 1980). Conversion to depth was accomplished by a velocity model based on interval velocities from well data. This resulted in the Winnipeg shale structure map showing a central uplifted high. Perhaps the apparent low in the Winnipeg shale was a velocity anomaly. The structure apparently fits some of the morphological constraints of a complex meteorite impact crater, (e.g. the supposition that a central uplift region exists) although they may not be as obvious as in many of the previous examples. This structure is a good example of how difficult it can be to make suppositions on genesis based on morphology alone. Furthermore, a lack of shock metamorphism leaves this structure classified as a possible impact crater only. (Westbroek et al 1996)

ABSTRACT

Because of the similarity between the Hartney anomaly of south western Manitoba and certain other oil-bearing features in the Williston Basin, a 1200 percent seismic reflection survey was conducted over this anomaly. These data showed an extremely complex, circular structure set in a relatively undisturbed regional geologic setting. By utilizing both migrated sections and seismic velocity analysis, a structural model was developed for this feature. Its structural configuration indicates that the Hartney anomaly is probably an astrobleme, or meteorite impact crater, of Lower Cretaceous age. A possible sequence of events resulting in this structure was postulated from existing seismic control and well data. (Anderson 1980)

References

[see – METEORITE]

Anderson C. E. A SEISMIC REFLECTION STUDY OF A PROBABLE ASTROBLEME NEAR HARTNEY, MANITOBA Canadian Journal of Exploration Geophysics 16:7–18 1980

Brent Dalrymple, Radiometric Dating Does Work! Reports of the National Center for Science Education

Sawatzky H.B. Astroblemes in the Williston Basin 1974

Sawatzky H.B. Buried impact craters in the Williston Basin and adjacent area Impact and Explosion Cratering p 461-480 1977

Westbroek H. Seismic interpretation of two possible meteorite impact craters: White Valley, Saskatchewan and Purple Springs, Alberta Department of Geology and Physics, University of Calgary

Hans-Henrik Westbroek and Robert R. Stewart The formation, morphology, and economic potential of meteorite impact craters CREWES Research Report — Volume 8 1996