. Occasional papers of the California Academy of Sciences . ntly intersected bysome of these faults. Seismic activity, however, is apparently lessthan on the Pacific side and damage has been comparatively small. A summary of the structural conditions in the isthmus indicatesthat in both eastern and western Panama, asymmetric anticlines fac-ing toward the sea are found on both sides of the country. Thesestructures are believed to be, in most cases, cut off by offshore thrustfaults dipping toward the land. Most of the structures facing theCaribbean are arcuate and convex to the north. Those faci
. Occasional papers of the California Academy of Sciences . ntly intersected bysome of these faults. Seismic activity, however, is apparently lessthan on the Pacific side and damage has been comparatively small. A summary of the structural conditions in the isthmus indicatesthat in both eastern and western Panama, asymmetric anticlines fac-ing toward the sea are found on both sides of the country. Thesestructures are believed to be, in most cases, cut off by offshore thrustfaults dipping toward the land. Most of the structures facing theCaribbean are arcuate and convex to the north. Those facing the Pa-cific are straighter but may be parts of larger arcuate folds. In 82 CALIFORNIA ACADEMY OF SCIENCES [Oc. Papers central and eastern Panama, a series of transisthmian faults intersectthe folds, and at some of the intersections there is indicated strikeslip, the general movement being left lateral. The transisthmian faultsstrike in eastern Panama, in the region of the CanalZone, and in Veraguas and Code. Similar transisthmian. Figure 8. Areal geology of Cana District, by Dr. H. Veacli. No. 23] TERRY: GEOLOGY OF PANAMA 83 faults probably occur in western Panama, but are obscured by Pleisto-cene and Recent volcanics. If the offshore thrust faults are projected downward they inter-sect, giving the isthmus the appearance of a wedge uplifted by pres-sure from both sides. These stresses have apparently arrived at anisostatic balance in eastern Panama, are slightly active in centralPanama, and are vigorously active in western Panama. The sinuousform of the country may be due to local variations in the pressuresfrom the two sides. The squeezing appears to have begun at the eastand moved westward. The elevation of the isthmian region which be-gan at the end of early Miocene time apparently had brought all ornearly all the region above sea level by the middle Pliocene. Wood-ring (1949) has stated the case as follows: According to vertebrate paleontologists f
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