The Vermillion Cliffs from the Gooseberry Plateau, south of Zion on the way towards the Chocolate Cliffs

Photos from the October 2013 Colorado Plateau Bedrock-Hosted Secondary Oxides field trip

In late October 2013, David Loope, Richard Kettler, Peter Mozley, and Derek Burgess led an excellent pre-GSA Meeting Field Trip to the Colorado Plateau to show a group of ~16 of us from all over the world some of the most fascinating features in the plateau: the geologic record of paleofluid flow in Mesozoic sandstones. The actual title of the trip was Early Mesozoic Sandstones in Utah’s Canyon Country: Signatures of Subsurface Microbes, Reducing Fluids, and Jurassic Earthquakes. The trip was a tour through some of the most geologically (and aesthetically) striking areas North America, through most of the Grand Staircase, and a chance to learn about and investigate the origins of widespread secondary oxide minerals in sandstones and what they have to say about paleogroundwater flow. We also looked at some fascinating features thought to represent paleoseismicity in Jurassic sandstones. Here are a few photos.

We started out the trip with evidence for reducing fluids migrating through the bedrock. Pretty hard to argue with here, as bona fide oil was seeping up along the Little Grand Wash Fault. This looks like the scene at the beginning of The Beverly Hillbillies when they say "Then one day he was shootin at some food, And up through the ground came a bubblin crude." You know the rest.

Huge expanses of thick travertine deposited in the last few decades by water flowing from Crystal Geyser, on the banks of the Green River. This is an artesian spring with boatloads of CO2 in it (and at least some H2S, as one can attest to from the odor) that started "erupting" after exploratory well drilling here a long time ago.

Amazing huge crusty piles of aragonite deposited in the strata just below the surface by upwelling CO2-charged fluids in the location of crystal geyser, long before it became a geyser. Apparently Powell and company stopped at this location to admire these deposits too.

The group heading out across the steppes towards the San Rafael Swell.

Deformation bands (sounds like ska-punk groups) in sandstone on the flanks of the San Rafael Swell. I had heard of these before but never appreciated how important and intriguing they are both from a deformational and fluid flow perspective. Apparently they are major impediments to fluid flow when not concentrated spatially.

Fe-oxide (goethite, hematite, probably) after pyrite, from a mineralized part of a traffic jam of deformation bands. This is what happens when too many deformation bands (otherwise impermeable) link up to form throughgoing fractures. The reduced Fe-minerals in these veins (later oxidized, obviously) seem to require reducing fluids.

Some fancy hiking boots, and our first glimpse of a chunk of "wonderstone," this one in Capitol Canyon in Capitol Reef National Park. This particular example is not winning any awards, but it did set the stage for later discussions and warrant a pulling out of the field trip guide for Loope et al.'s interpretation of the origin of these fascinating features.

A couple of our intrepid field trip leaders (Peter, center left; Dick, center right), standing over some incredibly complex and intriguing Fe-oxides in the Navajo Sandstone that record paleofluid flow. In this location, these flow structures are exposed in a wide variety of orientations, giving you a 3-D perspective on paleoflow, as seen in the next picture.

Flow tubules and sheets marked by bands of concentrated Fe-oxide cement.

World-famous geologist Brenda Bowen, pointing to a picture of herself in one of the Capitol Reef visitor centers. The caption says "Geologist studying iron concretions." Brenda has also done a lot of groundbreaking work on the paleofluid flow problems in the Plateau sandstones.
Crossbeds in the Navajo Sandstone with abundant carbonate cement concentrated along layers, and also in concretions. Apparently this calcite is ferroan too.
Some colorful wonderstone from Capitol Canyon.

This picture doesn't even begin to do it justice, but the cottonwoods (and several other kinds of trees) were going friggin nuts with the fall foliage schtick out there in Southern Utah, and the riparian zones were just ablaze with bright yellow. This shot is from the area between Escalante and Boulder, looking down into Calf Creek, I think.

As anyone who has been paying any attention when driving around Capitol Reef or the Escalante area knows, the tops of the ridges and plateaux are littered with basalt cobbles and boulders that seem to have no nearby source. Of course they do have a source several tens of km away up on a volcanic plateau to the north. Anyway, here is a shot of a conglomerate exposed on top of an interfluvial ridge. Apparently Marchetti et al. have dated this and other units to 0.3-1.4 Ma.

Another early morning shot looking SW over Calf Creek towards the Straight Cliffs.

Brenda Bowen in a pensive moment near a tremendous example of a concentrically zoned boxwork Fe-oxide formation in the Navajo sandstone down in Calf Creek. This is sort of wonder stone writ large. The short version of the the Loope et al. interpretation is that this started off as siderite, and then was attacked by microbes oxidizing the Fe from the outside in. This particular example is pretty compelling.

More boxwork Fe-oxide deposits in the Navajo in Calf Creek. The innermost core stone is considered to be residual siderite (now converted to oxide since shallow exposure) not fully consumed by the oxidation facilitated by the microbes that set up shop in that thick rind around it.

El Jefe Dr. Loope with an amazing example of what is essentially wonderstone texture surrounding residual, presumably older layering with completely different cementation patterns. Everything is oxide now, but the idea is that the interior was reduced, and being attacked by the microbes and oxidizing fluids surrounding it.

Next stop, the notorious Spencer Flat (after a stuck van in a wash of very soft sand, and a whole-field-trip pushing effort, sometimes from both sides of the van at once). Here, the world-famous Moki Marbles and similar cement blobs and plates litter the ground. It is really hard to resist stuffing your pockets with these oxide concretions. Most of the spherical ones are hollow, which raises interesting and important questions about how they form.

Unfortunately this picture doesn't convey it well, but many of the oxide cement chunks also have blobs of a very different textured cement--much more vitreous. Apparently it's not clear what this stuff is, but I have a bunch of it getting ready for some SEM/EDS analyses.

More Mokis forming desert pavement, penetrated here and there by prickly pear.

Dave Loope walking by a remarkable example (there are several here) of a joint along which Fe-oxide has apparently precipitated only on one side, in this case forming an erosion-resistant wall. The oxide seems to have precipitated in the joint, but then flowed away from it in reaction front tubes and blobs, but only in one direction...downstream towards the Colorado. Really striking.

Sort of mega-liesegang bands fingering their way downstream (to the right) from a fracture in the Navajo sandstone.

Leave it to Janice Gillespie to discover the nifty wine-bearing and -delivery utilities of open Moki Marbles. Here she is demonstrating with her little Moki golem friend (eyes from pinyon sap and very small Mokis). I did partake of the Moki communion too.

I had never seen the lesser known "Blue Cliffs" or "The Blues" of the Grand Staircase, here up high just before heading down towards Zion. The Blues are a huge thickness of late Cretaceous shale called the Kairparowits, noteworthy as being home to many excellent dino specimens, and one of if not the last place to be mapped in the lower 48. Up on top there is Paleogene Claron Formation (think Bryce, the most overrated place on the plateau).

It's hard to capture the beautiful foliage of ash, Rocky Mtn. maple, and others in these Zion slot canyons when all you have is an outdated old iPhone. But I tried anyway.

Some good examples here of lines of cylindrical (elliptical on a plane) paleoliquefaction escape vents (sand blows) preserved from Jurassic earthquakes in the dunes of the Navajo Sandstone.

The origin of Navajo seismites immortalized in the field guide.

A close-up of a cross-section through a sand-blow vent in the Navajo.

The modern morphology of so much of the landscape in Navajo seems to be trying to tell us that these were in fact huge active dunes awhile ago.

Another attempt to capture something of the fall foliage with cheap Apple products.

Just another late-morning jaunt across the crossbeds in Zion.

A small seep-fed stream coming out of and going across the Navajo Sandstone appears to be home to a community of somebodies making an oxidized iron crust. What is going on here, why is there Fe in solution so close to the surface, and who is responsible for it precipitating out in such creme bruleean crustiness?

Mmm, crispy caramel goodness.

After Zion, we headed south away from the Vermillion Cliffs, where it actually rained, and towards the Chocolate Cliffs, out on a vast plateau of Triassic sandstone.

Upon reaching the edge of this plateau, you find yourself at a massive escarpment capped by the Triassic Shinarump. This picture is taken looking south, and the lumps in the distance are Mt. Trumbull and its many other colleagues in the Uinkaret Volcanic Field, where I was just a couple weeks before this trip, at the edge of the North Rim of the Grand Canyon.

Beautiful boxwork oxidation rinds in the Shinarump sandstone on the Chocolate cliffs.

Dave Loope emphasizing a point beneath the Mormon Tea on the Shinarump. Directly in front of his hands is boxwork oxidation in cross-section.

Septarian nodule concretions in the Shinarump. The white filling is calcite, and supposedly there is bona fide siderite still preserved in the fine-grained, impermeable matrix surrounding it. This provides evidence for reduced-Fe concretions in at least some of the Mesozoic sandstones (probably early diagenetic in the overbank deposits of this unit).

More clear evidence for early diagenetic reduced Fe in the Shinarump: pyrite caught in the act of oxidizing in the vadose zone and leaving a beautiful Fe-oxide streak down a bedding-perpendicular fracture.

Dick Kettler at a truly gorgeous specimen of wonderstone in the Shinarump, or just stratigraphically above it.

Closeup of wonderstone, showing the two different types of Fe-oxide bands: the "main bands" with the obvious concentric pattern with smaller radius towards the upper left in this photo, and the finer-scale ones, often called liesegang bands, whose orientations are often at high angles to their bounding main bands. Often there is a bleached zone extending from one of the main bands into the liesegang zone. Another interesting observation is that there is apparently a correlation between width of a (main) oxide band and the distance to the next one, but only when considered in one direction; not the other.

A friendly and curious lizard (Common Sideblotched??) joined us for lunch at the Goosenecks of the San Juan.

Dave Loope getting ready to talk about a beautiful exposure of Mn-oxide mineralization in an abandoned Mn mine along a fault near Flat Iron Mesa, just south of Moab. Some very interesting geochronologic results have come from this location...