Thursday, February 14, 2008

Searching for NW-SE fractures in the Weak Zone Between Laverkin Quarry and Virgin Fissures near Virgin Town


Throughout the realms of conjectured Time
There occurs a thought which will not rhyme-
That Beings made with clay-like slime
Don’t fit the current paradigm.

We hunt in vain to find our mate
Who is made from aluminum-silicate;
And not just that, we take the bait
That like the horse- we evol(ate).

The horse we found upon inspection
Not only increased its resurrection;
But with its greater noise subjection
Became a cause-celebre correction.

There was no gradual evolution,
Rather increased air pollution-
Due to human elocution,
With greater Geological Dilution.

Now, feats of punctuated change
Descend upon us like the mange.
With a radioactive rearrange,
The genes, like mind, can soon derange.

When we make a mass defection
Back to Natural Selection,
We will make a gross detection
Of ol’ Nature’s predilection.

Now we view the past through time,
From the rocks, and frames they mime;
How an instant- so sublime-
Is preserved for future rhyme.

Simple time is in Man's head-
Storing there the vital thread,
Bathed in prisms, Gold and Red,
That ne'er wash out till he is dead.

Only He can keep the frames
That will harbor crests and flames,
In our lives- the dreams, the aims-
While whispering in our ear the Fames

Which while soon forgotten stayed,
In our minds' eye forever played-
As Aces in existence staid-
Those Frames of Life which we have made.

Harold L. Overton

The above Slickensides indicate a right-Lateral Fault by the groves and lines of incisions made as a graben dropped near the Hurridane Fault, Hf. We haven't found the confirmation of this feature in other locations of the Hf Scarp, but we did find some interesting rocks and artifacts in the zone of Investigation. These are shown below, and one can see these during hiking near the Laverkin Overlook Trail on top of the Kaibab outcrops just west of the Hurricane Mesa on the south side of Hiway 9.

An outstanding Mystery is the formation of Liesegang Rings, probably due to diffusion and precipitation of dissolved material in water, from a point source. These colored zones in this recently-split rock are not ring-shaped, but were photographed wet and dry to give you another part of the mystery to solve.

Notice the Parallel-ness of the Blue-tinted figure boundaries with the nearby rock surfaces- we'll name this arrangement Leisegang Polygons.

The upper Left-Hand corner shows local fractures, which orient N-S for reference.
Solve this Artifact's age and possible origin, considering that the Structure was on the edge of an incipient Wash, and was not fed by any flume for water storage (the top was above the land surface), and the cementing agent was mud, which would have been quickly eroded by stream flow. The mud cake seemed to be ancient, and the stones were layered limestone from nearby. The structure could have kept out rodents, if a lid could have been made fool-proof. One cannot climb into this artifiact withour ropes, as the sides are well-preserved.

Notice the Cistern-like appearance, which uses mud for sealing.

Try your hand at de-ciphering this young? construction (It is near an underground water pipeline)

North-oriented fractures are not subtle along the Western boundary of the Colorado Plateau.

The Laverkin Quarry has many parallel faults, running almost N-S, while the channel of the Virgin River has NW-SE and NE-SW orientations (making sharp turns, sometimes at abrupt right angles).
For this reason, we will hike from the Hf slickensides, where the fractures and faults definitely orient N-S, to the Virgin River, where the diagonal bends in the river occur. Somewhere in this space, we should find outcrops where the transition occurs. If we are lucky, we will find one fracture displaced by the other to determine the relative ages of the two systems.

Stress Indications from Fracture orientations Verde Valley, AZ has an outcrop of Limestone and other sedimentary rocks which displays many flat and level mesas criss-crossed by fractures. This formation, of Pliocene age, is no more than 5 million years old, so that if there have been earth stress direction change in times less than this age, it would show up in the rock fractures. This does occur, in the Pliocene rocks as well as in older Paleozoic rocks nearby. The Tertiary Verde formation, Tv, occurs in a tear-shaped graben, formed by the Mogollon Rim, Paleozoic Black Hills, and Tertiary basaltic dams to the south. It is cut by the Verde River, which has breached the dams as well as faulted rocks to the north. The whole entity orients almost N-S, and parallels other similar more northerly lake basins in NW Arizona, which altogether give the appearance of parallel diamonds hung on a necklace (separated by intervening uplifts and volcanoes).
In Tv there occasionally occur N-S and NW-SE fractures which intersect, on flat outcrops. This also occurs on Redbeds near Sedona, and there one may evaluate the fracture pattern change. I have observed that the diagonal fractures (NW and NE- their orthogonal companions) occur most often, and I assume that they have been instituted since the late Eocene, or early Oligocene- when the Laramide thrusting terminated, yielding to extension as observed in the dogleg in the Hawaiian-Emperor seamount chain in the Pacific Ocean (41 mybp age). Whenever the two orientations intersect, there is a displacement of one by the other. The fracture displaced (moved out of alignment) indicates the older orientation and this would have been accompanied by a concomitant stress change. The exercise below will be one to determine which is the most recent.
There are both N-S and NW-SE faults mapped by the geologists evaluating the outcrops for quadrangle maps, and this would lead one to expect to find similarly oriented fractures. The first question to answer is:
1. Do fracture displacements yield the same conclusions for both Tv and Paleozoic Redbeds? Secondly, since this answer is “not always”,
2. Does the older Tertiary faulting in Paleozoics occur also in Tv?
There is a significant Miocene fault running N-S through Oak Creek Canyon as well as west of Sedona (in areas with no late Tertiary), so that some N-S faulting preceded the formation of Tv. While there are many NW-SE fractures running parallel to the Mogollon Rim in Paleozoics, they also could have preceded Tv.
The possibility then exists that NW-SE stresses created shear beginning in Eocene and continued into the Miocene, and was superceded by N-S stresses- which would have fractured all rocks of all ages. The NW-SE stresses would have fractured rocks older than Pliocene.
I have seen Redbeds where N-S fractures are displaced by younger northwest ones, but in Tv it occurs the other way around- the N-S are the younger. This is buttressed by the occurrence of a line of anomalous springs, trending N-S from Soda to Winter Springs, through Montezuma Well.
There is one caveat for all this, occurring because of the expressions shown in CA fractures and faulting. The west coast orients NW, and continues on into the Pacific Basin, even after the coastline has re-oriented to the north near Mendocino (where the lateral Transforms turn westward to head out to sea). If one is to infer that the Pacific Plate movement has influenced the Basin & Range, B&R, all the way to the transition zone in AZ and UT, then one has to solve the dilemma of Ca having the youngest N-S Mammoth Lake fault expressions simultaneously with the San Andreas being active on a NW-SE orientation. There is no doubt that both of these orientations are active now- Mammoth Lake has violent thermal expressions running N-S, while the San Andres fault system continues to shear real estate to the NW (a right-lateral faulting system). Is it possible that there are two side-by-side stress systems, both active and both interfering with each other for a significant distance into their interiors?

What about our Hurricane Fault region, where the rocks immediately adjacent to Hf show N-S shear, while further away there are only NW-SE indications? The Laverkin Quarry has many parallel faults, running almost N-S, while the channel of the Virgin River to the south and east has NW-SE and NE-SW orientations (making sharp turns, sometimes at abrupt right angles).
For this reason, we have hiked east from the Hf slickensides, where the fractures and faults definitely orient N-S, to the Virgin River, where the diagonal bends in the river occur. Somewhere in this space, we should find outcrops where the transition occurs. If we are lucky, we will find one fracture displaced by the other to determine the relative ages of the two systems.

Fractures within one kilometer of Hf are monotonously N-S, and can be used for a compass.

The first kilometer of outcrops show no NW-SE fractures, possessing a monotonous array of N-S faults and fractures (hundreds) aligning with the obvious saddle north of Laverkin.
Covering the Paleozoic limestones to the east, the number of parallel fractures orienting N-S was amazingly consistent. A person lost under overcast or with no compass could use the rock fractures to orient his trek.
Occasionally there occurs a set of fractures orienting toward the canyon of the Laverkin Creek (east of the Laverkin saddle), trending 20-30 degrees from north. There was one case where a bend in the limestone fracture could be traced from N-S gradually turning to the NNE. Since there occurred no diagonally-oriented fractures in this border of Hf, the idea that there was a SE weak zone from the slickensides all the way to the Virgin fissures had to be abandoned. Instead it appears that a series of open fractures, tracing N-S and allowing the lands east of Hf scarp to slump readily, is the dominant occurrence. For this case, the interference of the Laverkin splay with the Hf saddle splay has created an extension of the crust to allow erosion and slumping to occur more readily. This can explain why there are many fault expressions in the Laverkin quarry area and why the slumping has created a more gradual slope to the highlands to the east. This allows a road to be developed (hiway 9) climbing the Hf scarp, which is a rare occurrence for the Hurricane Cliffs.
Now we must find why the Virgin River and near by open Fissures to orient to the NW and NE- since this is a definite indication of diagonal fracturing.
Some fractures cross the Virgin River, so could not be related to Spalling alone, but indicate a Previous Weakness (Old E-W Fracture, orthogonal to the N-S sets). Is it possible that the parallel N-S fractures exhibit an overall weakness, similar to that shown in the necklace of pearls arrangement exhibited in the Verde Valley- where a series of grabens or lakes form a NW trend of parallel N-S faults and fractures? If you sheared a block of material N-S,
( ¦
@ ↑ ¦ - arrow is stress direction, @ is right rotation) while bending it, you can create a series of strains which give this configuration.

We searched the flat and almost level CP edge from the Laverkin Overlook Trail to the Virgin River to the SE, looking for any outcrop which was un-moved from the bedrock, and which contained at least two parallel fractures.
The first general observation for this entire area is one of movement of limestone slabs under the postulated influence of ice expansion and soil heaving. The area has been highly weathered, leaving few original outcrops. This is normal for this elevation, where freezing is common- yielding prying of surface flagstones from the bedrock. The flags are rotated and moved around by the large amounts of soil which has been formed from the sandy limestone. This has occurred over the time since the plateau has been eroded down from the original Cretaceous and possible Eocene deposition (erosion after uplift- by several kilometers),
We proceeded with the assumption that the large Fissures near the Virgin River are simply the result of gravitational spalling and shearing after the river has eroded a large almost-vertical canyon. There is now an elevation difference of more than 100 meters in the deepest part, and this would create large shearing and compressive stresses due to gravity. The high bluffs and canyon walls would tend to spall off into the Virgin- parallel to it. Of course for every shearing strain, there is an orthogonal strain occurring because of the three dimensional effect of large chunks of stratigraphic columns acting independently of neighbors. The fractures to seek are the ones which are in neither of these categories- at oblique angles to the Virgin Canyon. Most of interest is the fracture aligning with the Laverkin Canyon to the north and that perpendicular to the Pine Valley Mountains, PVM.
Any fractures of Note will be those occurring in a set of at least two, which are parallel, and which cannot be suspected of having been generated by spalling into the young canyon (remember that there are fissures below the Virgin River- which were the ones taking the water from the dammed portion after diversion of the river for the new pipeline).

Many wide fissures occur a significant distance from the north bank of the Virgin, where some of them are not parallel to the River, but orient toward the Hf saddle to the north and others perpendicular to the PVM (which orients NE-SW)

Notice the Orientation- towards the PVM in the distance (this is to the NW)

A fisher named Fisher fished a fissure
For Brown Trout, a notable delight- a fish, sure!

But the fish, being fissile,
To the depths, went like a missile-
Pulling the fisher quite deep in the fissure.

The fish and his plan, readily outsmarted supercilious Man;
Now other fishers are fishing the fissure for ‘ol Fisher.

This boulder-filled fissure near tne Laverkin-Virgin confluence has more nearby smaller open fractures, which compare with the ones seen on the North side of Virgin River, west of Virgin Town- it is on the east side of a young Monocline and Hogback, west of the Ash Creek near Laverkin Town. The fissure orients N-S, and abruptly makes a left turn toward the west on part of the Monocline.

February 27/08, we trekked NE from the Laverkin Overlook Trail road, to the large open fissures above the north bank of the Virgin River. This is in flat country, with Paleozoic limestones, and which has mostly loose flagstones and soil. Although the loose slabs have mostly N-S fractures, these are discounted, since they are suspected of have been rotated by heaving of soil.
The first observation is that pertaining to limestone which has been left on small hills- these are less suspect of being moved by ice and heaving. There (in the 2nd km east of Hf) fractures are mostly oriented toward the Laverkin Creek and its eastern saddle.

The Fracture displaced is the Older- the Younger maintains its orientation

Notice that there is a trend toward the Laverkin Creek saddle, which is east of the Ash Creek saddle and drainage.

There is also a weak correlation of a Saddle to the SE with the fracture orientation.

Broadly, we did find that there were remnant NW-SE features, such as canyons at a 2 km distance from the Hurricane fault; the NW fractures may have been re-sealed by precipitation of calcite cement closer to Hf.

A Telephoto shot shows the same Canyon- a tributary of the Virgin- and its Diagonal fractures (NW-SE fractures are in the subsurface but difficult to find in the weathered surface Rocks (Due to re-sealing by calcereous cement).
Tentative conclusions are listed below:
1. The order in which fractures, created by regional stresses, occur through time is, older NW (diagonals), 20 degrees from north (Laverkin Creek-associated), and N-S (Hf associated);
2. Drainages in Zion NP were diagonally oriented and have become entrenched, under the NW-SE stress system;
3. Drainages formed in the Pleistocene orient N-S or E-W, the orthogonal set. This includes locally the Coal Pits, the Virgin, and Laverkin Creeks;
4. The first kilometer east of Hf is dominated by N-S fractures, with any NW-SE ones either non-existent or re-sealed by calcareous cement;
5. The second kilometer east of Hf is influenced by the Laverkin Creek system, with stresses oriented somewhat east of N-S; and
6. Finally, the old system initiated in early Cenozoic times- which created diagonal shear- has influenced the Virgin River turn-pattern and other canyons. All of the fractures systems are under the impetus of Extension, where rocks are being pulled apart. This allows rapid erosion and soil-building. Compressional systems, such as the uplift of 21 mybp Pine Valley Mountains, PVM, the 100 mybp Laramide anticlines and folds, and vulcanism are observable and are mostly older than Pliocene (except for Pleistocene volcanoes). The Hurricane fault should have compression associated with it, since there is an uplift of the western edge of the CP within the last kilometer of sediments. Hence, this may be a clue as to the incipience of Hf.

The next Mystery to solve is that noticed for the Hurricane fault in general. Within the first KM east of Hf, the sediments turn updip to the west. This is backward from that expected for an unlifting CP. My explanation is that deep Hot Magma upward movement in the past expanded the sediments (thermally as well as mechanically) close to the fault, attempting to rise. Those on the west side of Hf cannot be seen, since they generally are not exposed. See this feature in the upturned Kaibab or Timpoweep limestone shown in this same photo.

This Photo shows the area near the Hurricane Fault- where Chaos to the West replaces Serenity to the East.

Fractures and Fissures east of Hf by 2 km or more, near The Virgin:
The third foray onto the mesa north of the Virgin River, investigating the fractures which cut the various limestone layers at the ground surface told a different story compared to those nearer Hf. Photos are shown below which illustrate these conclusions. The surface rock may be Kaibab, Pk, or Timpoweap Trmt, but fractures and fissures were independent of stratigraphy- being a stress phenomenon.

A few Diagonal (NW-SE) fractures orient towards PVM,and some are criss-crossed by N-S trends.

1. N-S fractures were not dominant as they were for the first km east of Hf; both sets occurred, and NW-SE sets influenced the path of the Virgin River as well as fissures nearby and far away;
2. Other fractures were more noticeable, but these were not in sets of two or more, and appeared more random;
3. The 20 degrees from north fractures, which previously oriented towards Laverkin Canyon, gave way to N-S features. The distance to both Laverkin and Ash Creek canyons and saddles was sufficient to make the orientation similar for both visual sightings; and,
4. Large entities- such as river paths and large fissures- were influenced more by the diagonal orientations than by the younger Hf N-S fracture pattern. Although a major fissure may trend NW, indicating a major weakness, it may be composed of bends which are at 45 degrees from this orientation- either left or right of the average trend. This hints that the greater weakness, which may be somewhat cemented now, opens up to allow the younger strains (on a smaller scale) to be expressed.

Open Fissures, which are mostly parallel to the present Virgin River course, occasionally orient toward the PVM, and illustrate two perpendicular orientations (but the overall average direction is NW-SE).


Laverkin Hogback is oriented N-S, which is not normal for the area (Skewed referenced to other Mesozoic structures), except for Hf- the Hurricane Fault.

Standing on the Hogback, one may see the parallel paths of the Ash and Laverkin Creeks, which represent the sinking path of the monocline to the west.

The Stratigraphy of the Tertiary and Mesozoic is shown on the trail descending from Central Avenue (Laverkin), into the Tortoise Preserve.

Looking E from the Monocline, across the Laverkin and Ash Creeks, one may see all structures pointing down to the north near Hf, until reaching the basalt Plateau to the north. This structure, trending southward toward the same epicenter, will be Photographed from Ash Creek-Toquerville.

This View is toward Zion across the Creeks from Laverkin Monocline, and shows the Large Anomaly at Hf- which is underneath Laverkin Quarry.

Another View of Zion, from Laverkin Monocline (The Big Picture of the Laverkin sink must be taken from the north- Later!).

It is obvious that fissure extension is faster than erosion can fill the Openings.

Ben Everitt and another Hiker stand above a set of Orthogonal Fissures- which indicate the weaknesses presaging them.

The Influence of the N-S Fracture Orientation still manifests itself across the diagonal pattern of the Virgin Canyon.

The 3rd trip along the Virgin River, near Virgin town (west), produced more mainly N-S fissures and fractures, but occasionally there is a major one which is perpendicular to teh PVM

This locaation above the Virgin, north side, shows fractures which are diagonal to each other (45 degrees apart), indicating that both weaknesses may be exploited by the spalling above the Virgin Canyon.

The above comments pertain to Landscape near the proximity to the new (1985) dam on the Virgin, which is used to supply water for the Hurricane Valley.
This work has further disturbed the Crust near the north side and this may be reviewed elsewher in the Blog.

Laramide Geologists

Comments made aside-
From geologists with outdated pride-
Portray those who oft would hide
Behind the dead and ancient Laramide.