Hurricane Cliffs canyon (S26 T43S R13W) 3/2/05 Starting with S27, a canyon north of the AZ border, we investigated the retreat of the Hurricane Cliffs, to determine the age of the main fault. From my memory bank, as measured in Verde Valley- which is geologically similar (Permian cliffs) to this area in some respects- the House Mt. volcano, of age 13 my. originally lay against the Mogollon Rim and has since retreated by spalling of cliffs at the rate of 1 foot/600 years. Since the climate is similar to this here, and both formations are of Permian age, we will use this rate to determine when the Hurricane fault-canyon first appeared. I measure that the retreat is 1100 feet, using a 300 ft. tape. Using this 1100 feet, and 600 years/foot, this yields .66 million years since the fault first was significant enough to form a canyon for erosion and retreat. This does not mean that the cliffs are only of this age, but that the canyon is of this 6.6x10exp+5 age. We also want to determine whether there is a E-W fault which started the canyon process. There is a fair view of the contact of the Mesozoic and the Paleozoic where the fault evidently lies. The canyon crossing the gravel road is in the Mesozoic Moenkopi, where much gypsum is found in the wash. Above this rubble lies the Petrified Forest member of the Chinle, where the opalized logs and broken limb segments lie in their original stratigraphic configuration (as evidenced by a string of fossils along a contour on the hillside). Finally, the Navajo sandstone may be seen on top of the isolated mesa, which lies west of the cliffs. We will try to isolate the Moenave and Kayenta, which lie between these two Mesozoic formations- they are both thin, oxidized, coastal deposits, with some shallow marine members. The canyon walls surrounding the wash increase in height to the east and finally produce indurated rock, which is mainly Moenkopi and younger. The general dip of strata is generally up to the west (on both sides of the main fault), but at the old line where the cliffs originated the beds dip up to the east, finally becoming vertical- assumed to be the contact of the fault with the older uplift. The measurement of the distance from these vertical beds to the present cliffs is the amount that the cliffs have "walked" since canyon cutting has commenced. The assumptions behind this are: 1.The uplift before this verticality occurred has been eroded to yield an outwash plain, or is insignificant (there was probably uplift before this time, but has been almost leveled). When one walks a distance to the south of the wash, you will see large boulders on an outwash plain, which do not appear to be very old, indicating a previous erosional surface almost level. The whole entity is probably ancient, and the fault has been rejuvenated, as is indicated further north in the Wasatch Front; 2.The canyon mouth created by the uplift and possible cross faulting has spalled off starting wth the Pleistocene uplift, and has proceeded uniformly until now; 3. As with the Mogollon rim, the ancient fractures from previous stresses have been preserved (in a N-S orientation) and have allowed the cliffs to spall off, rather than round off by normal erosion, and the cliffs "walk" by remaining vertical while spalling periodically (the shear strength is much less than the compressive strength). 4. Close to the canyon mouth, there appear increasingly thick gravels- conglomerates, of significant strength. These can be incorporated into the strength-age scheme introduced for Zion Park gravels near the hiway 9. The strength is seen to be similar (somewhat older), of a Pleistocene age. Since the gravels occur in thick amounts, this suggests that the canyon appeared suddenly and caused considerable erosion within a short period of time- as if a stream "found" a cliff to erode. The first gravels contain cobbles and smaller sizes, but within a few vertical feet, large boulders appear. This introduces a complexity into the equation of age calculation, hence we will only calculate the age when the canyon first caused gravels to suddenly occur. The presence of the cliff, eroded by the first stream, means that a large scarp was already present when the canyon first appeared. We might estimate the age of the scarp from the thickness of the gravels and work backweards, but probably there is an previous age of significant uplift and erosion unaccounted. By the punch test, these conglomerates near the cliff mouth, are somewhat older than the ones found at Coal Pits wash- I would estimate that they are near 1 my.- possibly Pliestocene (which lasts backwards to 1 my.) Some of the black basalts found at the top of the rim (indicating they were there before the main cliffs were formed) are of this age of more than 1 my, as indiated by their rounding by ordinary erosion by precipitation. 5. This canyon, which we will call Honeymoon, from the trail above it, deadends in a box, where a waterfall was laboring on the north side. There is very little erosion above the box, but the Topo for this area shows that the feeding stream runs almost due north. This would be in the same direction as the Hurricane fault, and there probably are N-S fractures parallel to the main fault, which have been "found" by a modern runoff stream (the stream above is not deep, and has caused very little erosion of the Kaibab limestone). Mesozoic beds' dip significance The fact that the mesozoic strata dip up to the west on both sides of the Hurricane fault means that whatever created the fault had a thin zonal effect- not a local uplift, as with an intrusion or anticline. Rather, the fault is a slice caused by a large region (edge of the C.P.) shearing away from another large region- that is, the transition from the basin and range. This case has already been documented, for a dipping of the Eocene beds up to the west,while the underlying Mesozoic dipped oppositely in the Cedar City area. In our area, at Toquerville, and at Laverkin, the post-Laramide dip continues right across the Hurricane fault, even though the displacement is large at the fault. This means that entities south of the Pine Valley Mts. have been first subject to compression from the west, then later sliced by some simpler action. We will check that this generally is the case, and if positive, this means that vulcanism, N-S faulting, and extensional faulting are operating under a separate system than that north of the P.V. mtns. The sequence would be as follows: 1. Compression from the Pacific plate moving eastward in Cretaceous times created anticlines, monoclines and folds oriented N-S here (as with the Kaibab plateau, as seen along the Lee's ferry to Cameron road; 2. These stresses died away in Oligocene times, allowing the area to become extensional (after the time of the dog-leg in the Hawaiian-Emporer seamount chain, of 41 my. time); 3. Wrenching in Oligocene times was toward the NW- creating the omnipresent NW-SE fractures over most of the West US; 4. Some 2 my.ago, the original N-S weaknesses, created by the east-stressing Sevier and Laramide plate movement, were rejuvenated by extension (this is seen in the Verde ls. in Verde Valley- which is younger than 5 my, and in N-S rivers such as Rio Grande, Verde, and south Colorado Rivers.); 5. Vulcanism started- first the basaltic type, as seen in our area as a clean contact of Mesozoic below basalt with hardly any ash or gravels in the contact. The most recent extrusion has been of the ash fall type- in Hawaii, this is noticed as a rejuvenation phase, some 1-2 my. after the individual islands were isolated by eruptions further to the SE. The rejuvenated alkalic lavas tend to be on the SE side of islands (such as Diamond and Koko Heads); 6. The vulcanism has moved westward, in the transition zone- the youngest noticed is off hiway 18 near Snow Canyon. In AZ there has been a westward movement of extrusives also, but in this case over a 20 my. time span, and well off the C.P. into the basin and range; 7. Uplift along the Huricane fault continues, and the fracture indications in Zion Park appear to have been re-oriented from NE-SW (as with the P.V. Mtns) to 160-340 degrees from north. One can see major canyons orienting in these two linear arangements, while the older drainage tends toward the NE-SW (with the younger tending to be more N-S, as with Coal Pits Creek). Questions: a.Do the younger volcanic cones orient toward the N-S, in our area? b. Do recent earthquakes align along a N-S axis here, as contrasted to NW-SE in the Grand Canyon area? If so, we have isolated our system here from that further south, where the C.P. exhibits behavior for the SW side, as opposed to our being on the west side where fracture behavior would be expected to tend N-S. c. We still have to explain the NE-SW orientation of the P.V. Mtns. and Virgin anaticline, which should have been oriented N-S- if only under the onus of the east-moving Pacific plate? The author hiked westward of the large mesa at the Honeymoon canyon, runniing 160- 340 degrees along the Hurricane cliffs, to determine whether the beds dipping up to the west formed an anticline which had been breached and eroded at its central portion. This is mostly buried, but there is an exposure of Moenkopi to Chinle, dipping upward to the west still, at a dip angle of 45 degrees terminating in the air- about 1 mile to the west of the Hurricane cliffs. To the south one can see a slight dip of beds down to the SW, and this may be a separate feature- this must be investigated further. Harold L. Overton