Geology Reference
In-Depth Information
Fig. 6.25.
Cross section produced by the method of circular arcs.
A
-
I:
outcrop dip locations;
A
i
:
marker
horizons;
O
i
:
centers of curvature. (After Busk 1929)
Fig. 6.26.
Sensitivity of the crest loca-
tion on a circular-arc cross
section to the dips in the adja-
cent syncline.
A:
Dip on sur-
face anticline used for linear
projection of the fold limb;
B
-
D:
dips in adjacent syncline
used for circular-arc construc-
tion of the limb;
O
i
:
centers of
curvature. Wells attempting to
drill the lowest unit at the crest
are shown. (After Busk 1929)
curvature is located at O
1
. The marker horizon is extended to the normal through C as
a circular arc with center O
1
. The same procedure is followed across the section to
complete the key horizon A-A (Fig. 6.25). The remaining stratigraphic horizons are
drawn as segments of circular arcs around the appropriate centers. Constructed in this
fashion, the beds have constant thickness. To maintain constant bed thickness, the beds
form cusps in the core of the fold.
