Validation of Sediment Accumulation Regions in Kansas, USA
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gions bounded by B, C, and D boundaries also roughly correspond to the Peace
Creek Tectonic Zone recognized by Berensen (1997), which he attributed to reactivation of the Midcontinent Rift System.
In southern Kansas, the southwestern portion of boundary E also seems to
follow northeast-southwest trends associated with the Midcontinent Rift and
appears to cut across a saddle between two gravity highs along the rift trend, as
axial gravity high north of the boundary trends to a more northern direction.
The northern extent of boundary E, however, curves to an easternly, then a
southeasterly, trend as it approaches the northern margins of a gravity high,
which is probably associated with deeper mafic intrusive activity along the Midcontinent Rift System. The curve of this boundary also appears to correlate with
the northern margin of the Southern Granite-Rhyolite Province, which is interpreted from previous work on magetics (Yarger 1983) and age dating of well cuttings (Van Schmus 1992; Van Schmus and Bickford eds. 1993; Van Schmus, Bickford, and Turek, in press).
Boundary F is much like boundary E. The southwestern parts of boundary F
follow the northeast-southwest Midcontinent Rift structures and curves to the
east along the northern portions of this boundary. The northern portions of this
boundary also appear to follow the northern margins of the large magnetic high
probably associated with the Southern Granite-Rhyolite Province.
Boundary G appears to cut obliquely across the Midcontinent Rift System as
the boundary trends in a east-northeast, west-southwest orientation. In addition, this boundary is somewhat irregular towards the east. However, the northwest-southeast trend of the northern margin of this boundary roughly correlates with northwest-southeast structural lineaments as well as gravity and magnetic lineaments. The easternmost part of this boundary turns abruptly to a
northeast-southwest trend, and may be related to structures associated with the
easternmost flank of the Midcontinent Rift System.
A second set of SAR boundaries are described from western Kansas, boundaries X, Y, and Z. The second set contrasts with the first set as they trend perpendicular to them. SAR boundary X closely follows arcuate-shaped gravity anomalies probably created by structural deformation and granitic intrusions associated with the Central Plains Orogen. This boundary also closely corresponds to
a trend of isolated magnetic highs, interpreted as epizonal granitic intrusives
(Yarger 1983) that occur near the northern margin of the Southern Granite-Rhyolite Province and may be close to the same age (Van Schmus et al.1993). Previous workers have suggested that the northern margins of the Southern GraniteRhyolite Province may simply be an erosional boundary. Close correspondence
between the northern margin of the Southern Granite-Rhyolite Province, both
gravity and magnetic trends and accordant sites of Paleozoic structural reactivation, i.e., SAR boundaries, suggests that this boundary may in fact be partly
structurally controlled.
Boundary Y is another arcuate trend. It closely follows the arcuate trend of
gravity and magnetic anomalies to the north between itself and boundary X. Although the region associated with this boundary terminates in the southeast, the
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gions bounded by B, C, and D boundaries also roughly correspond to the Peace
Creek Tectonic Zone recognized by Berensen (1997), which he attributed to reactivation of the Midcontinent Rift System.
In southern Kansas, the southwestern portion of boundary E also seems to
follow northeast-southwest trends associated with the Midcontinent Rift and
appears to cut across a saddle between two gravity highs along the rift trend, as
axial gravity high north of the boundary trends to a more northern direction.
The northern extent of boundary E, however, curves to an easternly, then a
southeasterly, trend as it approaches the northern margins of a gravity high,
which is probably associated with deeper mafic intrusive activity along the Midcontinent Rift System. The curve of this boundary also appears to correlate with
the northern margin of the Southern Granite-Rhyolite Province, which is interpreted from previous work on magetics (Yarger 1983) and age dating of well cuttings (Van Schmus 1992; Van Schmus and Bickford eds. 1993; Van Schmus, Bickford, and Turek, in press).
Boundary F is much like boundary E. The southwestern parts of boundary F
follow the northeast-southwest Midcontinent Rift structures and curves to the
east along the northern portions of this boundary. The northern portions of this
boundary also appear to follow the northern margins of the large magnetic high
probably associated with the Southern Granite-Rhyolite Province.
Boundary G appears to cut obliquely across the Midcontinent Rift System as
the boundary trends in a east-northeast, west-southwest orientation. In addition, this boundary is somewhat irregular towards the east. However, the northwest-southeast trend of the northern margin of this boundary roughly correlates with northwest-southeast structural lineaments as well as gravity and magnetic lineaments. The easternmost part of this boundary turns abruptly to a
northeast-southwest trend, and may be related to structures associated with the
easternmost flank of the Midcontinent Rift System.
A second set of SAR boundaries are described from western Kansas, boundaries X, Y, and Z. The second set contrasts with the first set as they trend perpendicular to them. SAR boundary X closely follows arcuate-shaped gravity anomalies probably created by structural deformation and granitic intrusions associated with the Central Plains Orogen. This boundary also closely corresponds to
a trend of isolated magnetic highs, interpreted as epizonal granitic intrusives
(Yarger 1983) that occur near the northern margin of the Southern Granite-Rhyolite Province and may be close to the same age (Van Schmus et al.1993). Previous workers have suggested that the northern margins of the Southern GraniteRhyolite Province may simply be an erosional boundary. Close correspondence
between the northern margin of the Southern Granite-Rhyolite Province, both
gravity and magnetic trends and accordant sites of Paleozoic structural reactivation, i.e., SAR boundaries, suggests that this boundary may in fact be partly
structurally controlled.
Boundary Y is another arcuate trend. It closely follows the arcuate trend of
gravity and magnetic anomalies to the north between itself and boundary X. Although the region associated with this boundary terminates in the southeast, the