Sunday, July 31, 2011

Accretionary Wedge #37 - Sexy Geology

No, Geology is not a fetish for me. Sometimes an obsession, but not a fetish - there is a difference.  Without going into any unnecessary detail, I will just list my favorite rock units, as this part of AW #37.

For photographic purposes, I related my "current love" for the Jurassic Navajo Sandstone, in my "What a Geologist Sees - Part 36".  I haven't been in the outcrop area of the Navajo Sandstone for many years, but through some of my old 35 mm slides and digital photos given to me by friends - I have developed a great appreciation for the eolian cross-beds and the diverse settings in which the Navajo is exposed on the Colorado Plateau.

For fossil-collecting purposes, I would have to say that the Late Eocene limestones of the Georgia Coastal Plain and the Florida peninsula.  Of greatest interest - to me - are the diverse array of irregular echinoids with a small, but nice assemblage of different scallops (Chlamys and Pectin sp.).  On a smaller scale, there are also small comatulid crinoids and very small brachiopods at some of the localities.  In the Savannah River area of Burke County, there are occurrences of the large oysters Ostrea gigantissima in the Griffins Landing Member of the Late Eocene Dry Branch Fm.

The widespread distribution of limestones (close to the Fall Line) and other evidence suggests that the Eocene, especially the Late Eocene was a time of warm temperatures, friendly to biodivesity.  The Ocala Limestone in Florida is the dominant Late Eocene rock unit in Florida.  Updip in Georgia, there are a number of different limestone units of interest, as well as the sandy Clinchfield Formation.

The first Late Eocene locality that I visited was the Tivola Limestone, in the Perry, Ga. area, in Houston County.  This sand dollar was from that undergrad field trip, from the old Medusa Quarry, SE of Perry.  This sand dollar is also found in the Tivola-equivalent at the Rich Hill quarry, just 2 miles from the Fall Line, NW of Macon.

Unless there have been some interpretational changes in the strat sections, the Sandersville Limestone is one of the youngest of the Late Eocene units in the Georgia Coastal Plain and the Periarchus quinquefarius was the last of the 3 (or 4) Periarchus species in Georgia.  The Ocmulgee Fm. is a downdip equivalent of the Sandersville.  Periarchus lyelli, from the uppermost part of the underlying Middle Eocene Lisbon Fm. and the Clinchfield is the first of these, followed by P. pileussinensis, then P. quinquefarius.

This smaller irregular echinoid is from near Leesburg, GA, in the old Starkville quarry.  If memory serves me correctly, this is the equivalent to the limestone exposures at the northern end of Albany, near the "power dam" on the Flint River.

I traded for this specimen from the Florida peninsula.  There are numerous other Late Eocene echinoids in my collection, and there are other Georgia collecting localities, some now inaccessible.
Presumably, it was the end-of-Eocene Chesapeake bolide impact that triggered a regional extinction event, which wiped out a number of the Late Eocene echinoid taxa or at least those in certain updip facies. 

Yeah, I guess I am sort of in love with the Late Eocene of Ga. and Fla.  Just don't tell my wife.

[Update:  I seem to be having trouble with my Blogger account, it is giving me grief when I try to comment on my own post.  So thanks to all that leave positive and useful comments.  I am not ignoring you, the system just has a glitch.]

Saturday, July 30, 2011

Accretionary Wedge #37 Seeking Posts on - Sexy Geology...

August 26th is the deadline for your photos and stories of "Sexy Geology".

The host site - "Outside the Interzone" describes the desired type of story as: "...geology that makes your heart race, your pupils dilate. Rocks and exposures that make you feel woozy and warm. Structures and concepts that make your skin alternately sweaty and covered with goosebumps. Places you've visited, read about, or seen photos of that make you feel weak-kneed, and induce a pit in your stomach."

The original Accretionary Wedge site has this link on the subject.

This brings forth some interesting thoughts and I will try to have something, soon. Without getting "racy", that is. People think we are crazy enough as it is.

[Note: For what it is worth, to avoid any confusion, my regular "What a Geologist Sees" Parts 36 & 37 happen to chronologically coincide with Accretionary Wedge Posts #36 and #37. This is by shear accident.]

Tuesday, July 19, 2011

What a Geologist Sees - Part 36 - The Navajo Sandstone

[A minor disclaimer - I am not 100% sure that this is the Jurassic Navajo Sandstone, there are other eolian sandstones in southern Utah, but I am going with the assumption that this is Navajo.]

This "wow" photo was taken earlier this summer by a couple from our church while they were on vacation in Colorado, Arizona, and Utah.  They were kind enough to give me copies of their photos for educational use (and those will be captioned and attributed).  As my budget and schedule doesn't permit such excursions, I am grateful for their photos - past and present.  This is their first "digital trip", as past trips have been photographed on 35-mm film, necessitating scanning of prints or slides. 

The above photo was taken along Utah Scenic Byway 12, somewhere near Zion National Park.  This couple - Bob and Jenny - are very good about creating scrapbooks and logs of their travels and collecting all sort of info from the National, State, and local parks that they visit.  But sometimes it is some of the "in-between" photos that are hard to locate (or else I can't find the same scenes photographed by other people - for ID purposes).  I have several other great photos (for educational purposes) of the Navajo Sandstone.

This is another of their photos from this year, of "Checkerboard Mesa" in Zion National Park.  An image of Checkerboard Mesa used to grace the cover of one of the Physical Geology lab manuals we used to use.

This photo from Upper Antelope Canyon (from a scanned negative) is from a previous western trip.

Though I haven't visited any outcrop areas of the Navajo Sandstone for years (decades), from my past photos and newer photos given to me, I would have to say that the Navajo Sandstone is my "favorite" sedimentary unit for photographic purposes. I don't know of any fossil-laden areas of the Navajo, it is the large-scale eolian cross-beds that make for great photographs and educational teaching tools.

[BTW, for fossil-collecting purposes, I would have to say that the Eocene Ocala Limestone (and similar-aged units in Georgia) is my favorite sedimentary unit.]

Saturday, July 16, 2011

Accretionary Wedge #36...Stuff Left Behind, With Regrets

What have you left behind in the field? What have you lost or what do you regret not having collected, including photographs?  [Before going further, I would like to thank all of the participants.]

The first contributor, Evelyn Mervine recounts some fascinating field work in the Indian Ocean, then she goes on to relate what she regrets not bringing home - a baby goat or a baby camel from Oman. I wonder what U.S. Customs would have had to say about that? [I once used a large paper cup to catch a kangaroo rat (for a few minutes) in the Eagle Mts. of West Texas, but it wouldn't have acclimated to a caged existence.]  If one lived on a farm, bringing home such "souvenirs" from the field might work, but not so sure in a two-bedroom apartment.  I don't know whether goats and camels can be housebroken.  Here is her post in its entirety. 

From Ann's Musings on Geology, Ann muses on her extensive 35-mm photographic past and photos she didn't get. She recounts such issues as not wanting to expose her camera to adverse conditions, e.g., dust or rain or not wanting to carry the extra weight. [Been there, done that on both counts.] She also described the familiar college-student issues, such as the expense of film purchases and development costs. As I did, she chose slides as they were cheaper. Another constant issue with 35-mm film photography, you had to wait to know if you got one or more decent shots.  Many times, once she found out that she didn't get a good photo, it was in a situation where there were no do-overs, no chance to revisit the site.  [Another 35-mm hazard - forgetting to reel the film back into the cartridge before you open the back of the camera.  In 1982, I lost all of my Wisconsin glacial features slides when I did this.]  As I do, she now faces the dilemma over what to do about all of those slides and how to convert them.  Hopefully this can be resolved in a satisfactory way, with a scanner of some type.  [I have a scanner, but not the time.]

Dana Hunter also reminisces about the Photo Not Taken. Actually of the photos not taken when she lived in Arizona. The empty photo-box syndrome. I can attest that there is plenty of good geology to be photographed in all of Arizona, especially the northern half of the state...San Francisco Peaks, Page, Sunset Crater, Grand Canyon, Sedona, Jerome, Barringer Crater, Canyon de Chelly, Shiprock,...

Silver Fox at Looking for Detachment is the first to report on regretting leaving a geological/archeological item in the field.  From her account, after being literally dropped-off by helicopter at a field site: ..."I found a large pink projectile point in the middle of the drainage I was walking down, a drainage that had obviously seen some flooding in the last 1 to 5 years. The point was possibly made of Ivanhoe "chert" (more precisely opalite or silicified tuff) from the Tosawihi Quarries of northern Nevada, a large series of rock quarries made by ancient to nearly present-day native Americans..."   In following accepted archeological protocols, she left the point, intending to mark the locality on a map for later collecting by a "trained professional".  For whatever reason, the info didn't get passed along and the point was probably washed further downslope with later weather events.  [I once got a polite lecture from a friend about collecting a silicified limestone "hand tool" from a roadside site, but I was able to drive him to the site and point to the exact location, so he could relate it to his archeologist girlfriend, so no damage done.]

The next contribution comes from Egypt!  Way cool.  Selim Abdelrhman reports on the strange rocks of Wadi Elbattekh in Egypt.  From his words: "OK, Wadi Elbattekh or وادي البطيخ my translation is “Watermelon Valley” it’s a Wadi filled with strange rock shape and very soft in touch. i think the origin of this rocks is still a mystery."...

From Casey at Gioscience comes regrets of not having collected more samples (and taken more photos) of ripple-marked sandstones during at 1998 GSA Southeastern Section fieldtrip in WV, a fieldtrip that included the legendary sedimentary petrologist Bob Folk.  The ripple marks were in the Devonian Foreknobs Formation, part of the Catskill Delta.

The proprietor of GeologyMelange brings us his first geoblog post.  The subject of regret was a past visit to part of Marble Canyon in Death Valley.  Of most interest was an apparently un-mapped outcrop of deformed crinoid "hash".  There were a sufficient number of photos taken, but no measurements were taken of the size or orientation of the outcrop and not enough samples were collected.  But of even more interest were the cobbles of white marble, the origins of which were not discovered.

A photo of Christopher with a fault-breccia in Marble Canyon, just above the canyon sediments.

Ron Schott admitted not collecting enough samples from certain sites, taking enough notes, or taking enough photos.  But his greatest regret was losing his first Estwing Rock Hammer, which he was given as part of his Colgate Univ. Field camp gear.  It served him well in field camp, but when he visited Giant Mountain in the Adirondacks, the spirits of the mountain became incensed at his collection of samples of the Roaring Brook intrusion breccia.  The spirits extracted their revenge by relieving him of his beloved hammer from its improvised rope belt.  [I know the feeling.  My Dad gave me a brand new Estwing Rock Hammer when I left home to go to UTEP for grad school.  Despite having the handle wrapped with day-glow orange tape, I managed to lose it in the Eagle Mts., about a year and a half later.]

Jessica Ball (aka Tuff Cookie) has a similar story of losing a "first piece of field equipment", a little smaller, but still important.  Somewhere in the area of Sugar Hollow in the Virginia Blue Ridge Mountains, her first hand lens slipped off its lanyard.  From a separate adventure, she regrets not having kept her first pair of hiking boots, with partially-melted soles from an encounter with some of Kilauea's fresh lava flows.  I am sure that those boots would have been good for some stories.

For my contributions, there are actually two different ones. In 1979, I had a summer job in the San Juan Basin of NW New Mexico, as part of a fossil recovery project, prior to the opening of an open-pit coal mine. Outside of our project area - on the road back to the dirt "highway", there was a reddish-colored outcrop of "clinker" material, i.e., baked Cretaceous shale with plant fossils. The baking was probably courtesy of an ancient, underground coal-seam fire. After driving by this site to - and from - my "days off", I decided to stop and have a look. I regret only picking up two specimens from this site, one (pictured) with an angiosperm leaf and a stem fragment and another with a piece of a stem. WHY DIDN'T I AT LEAST FILL A BUCKET FROM THIS SITE? I will never know.

The image is labeled for use in my classes.

The other under-collected site was the previous summer, when I was in the Eagle Mountains in West Texas. While surveying the area - as part of a planned thesis project, which was never finished, in favor of another a few years, later - amid the caldera breccias and ash flow tuffs, I found a chunk of siltstone, with some tiny impact craters. I regret not even doing a rough draft of the extent of this intra-caldera siltstone. It most likely was reworked, water-deposited ash, with roughly-defined bedding planes. The surface was marked by a few tiny impact craters, suggesting bombardment by explosion debris, while the upper surface was exposed, but soft and "plastic". Looking at cross-sectional view, there was evidence of other small impacts by broken crystals/rock fragments. I often include this in lab instructions to remind students that it is possible to find sedimentary rocks inside of volcanoes. SO WHY DIDN'T I PICK UP MORE CHUNKS OF SILTSTONE?  [BTW, the place where I lost my Estwing rock hammer was a stop or two past the siltstone locality.  Hmm, is there a connection?]

[Update: A couple more attendees to the party!]

Water and Rocks...At The Same Time reports on the discovery of a chevron fold in an outcrop of the Dolgeville Fault on a tributary of the Mohawk River, near Dolgeville, NY.  The photo at left shows a portion of the fold.  Several members of the field trip party picked up folded portions of (presumed siltstone), but Roy didn't want to add anymore clutter to the crowded van (be there, done that on a crowded field trip bus, it is hard to keep samples organized and under control).  This was his 2nd chevron fold, the first he donated to his alma mater, SUNY Oneonta.  Roy, you have my permission to collect the next chevron fold for yourself.

Dr. Ian at Hypo-center reports on some important items ALMOST LOST during field work in Lukmanier Pass region of Ticino, Switzerland years ago.  After picking up a fair-sized sample of gneiss: ..."I was crossing a boulder field and noticed an interesting looking exposure up a steep face to my right. I put my notebook down on a rock, placed my map case on top of it, and my gneiss sample on that to stop it blowing away. I then headed up to the steep outcrop with my compass-clinometer thinking I could easily remember a couple of readings and rock details and return to record the information in my notebook."...  After climbing upwards to check out more interesting metamorphics and record several more structural readings, he turned around to re-orient himself and return to collect his sample, notebook, and map case, when he realized - "Just damn! - all them boulders look the same!" (or something like that).  More from Ian:  ..."After an hour a mild panic started to set in. Had I just lost three weeks work down to my own stupidity? Since I knew that they had to be in the boulder field somewhere,..."  He searched for two more hours.  At the point of almost giving up hope, he decided to do two more passes through the boulder field, then he realized that the items of interest were a mere 10 meters away from him.  But a sad postcript follows this reunification of geologist and field equipment...  ..."After my degree, I went to Cardiff to do a Ph.D. and I told the metamorphic petrology lecturer about the wonderful metamorphic rocks at Lukmanierpass, including hornblende garbenschiefer and kyanite schists...I showed him the box of my rock samples that I had collected there. He asked if he could hang on to them for a while and I agreed. With the passing of my Ph.D. I completely forgot that I had lent him the rock samples. I moved on to Keele, and he moved on from Cardiff."  So the location of the box of rocks is a mystery.

Well, us Geologists and our stories of "the ones that got away".  Maybe some younger folks will learn something from our travails, lost samples, unphotographed localities, lost equipment, and regrets.

Thursday, July 14, 2011

An Interesting Video...

Golden Scientific Ages in Islam, from the blog GeoSelim from Abdelrhman Selim, a contributor to the ongoing Accretionary Wedge #36.

Interesting info and perspective.

From my more recent understanding of climate history, it seems that what we call the "Dark Ages" was a part of the Dark Ages Cold Period, a time of rather bad weather (and all that goes with it, such as poor crop production) in Europe.

The "Science" of Stained Glass

Stained glass, as a hobby, was taught to me by a couple of friends about 30 years ago. I did a few panels and sold them in the El Paso area, then once I met my wife, I had other priorities.

I recently resurrected this hobby, in order to replace a clearlite that I was too cheap to "hire out" - to have done. I have plans for the other one, hopefully it will be finished in a few weeks.

The entire panel is 53" x 7", the longest panel I have ever done and the first in close to 25 years.  It turned out as I wanted it.  Random splashes of color, with interspersed sections of clear antique and glue chip.

The next one (to the left of the door) will be similar.  I thought of doing random splashes of color with slightly curved lines, but I decided that it might be "too different", i.e., too much contrast.

If I like the second one more, I thought about swapping this one to the left side, but handling such a long panel is risky and the copper foil joints are not as strong as the lead ones, so maybe I will just leave well enough alone.

Here is a close-up of the top.

Here is a close-up of the bottom.  I chose to make the lower 1 foot opaque, so the dog wouldn't be tempted to lean on it, if she saw something through the window (she has other windows for that purpose, to bark at squirrels, pedestrians walking their dogs, etc.).  She has actually broken through two smaller window panes to go chase squirrels.  I hope she has forgotten that "skill".

It may be a bit of stretch, but one could make a comparison of learning how to properly cut glass (and how to clean up all of the tiny flakes and slivers) to the practice of science principles. I will probably leave those details to a later discussion. Hope you enjoy the photos.

[Actually, I have included slivers of polished agate in some small, experimental glass panels before. Might do that again.]

Sunday, July 10, 2011

Tennessee Landslide

No, this is not a new one, but it is a "geo-favorite" of mine as I have driven this section of U.S. Hwy 64, along the Ocoee River several times. Though this is a small landslide, the "carrying-along" of the trees is impressive to students.

The newsmen discuss making the video:

Of importance is the way the gentleman in the red shirt discusses the sounds that preceded the slide. Listen to nature!

Part II, from YouTube user "wdef":

Tennessee Geologist Vanessa Bateman was responsible for clearing the area of TDOT workers, journalists, etc.. To review, there had been a small landslide and the various observers had gathered to look and the TDOT workers had gathered to start cleaning the road. Apparently, Vanessa arrived, looked and listened to the mountain-side and decided "this ain't over, yet." and ordered people and equipment out of the area. Thankfully, they listened.

To add a little local geo-info, this area is in SE Tennessee and the rocks here are mostly slates and other low-grade metamorphics of Precambrian age (if memory serves me correctly). As you can see, many of the fractures/rock-cleavage planes are dipping towards the highway, so after heavy rains, this area is always going to be susceptible to landslide events.

In closing, this is a geo-favorite because (in no particular order):

1) It shows nature in action.
2) It is "local" (in terms of Southern Appalachians).
3) No one got hurt.
4) A Geologist was the hero. Sometimes we don't get no respect from engineers - been there, done that - on a less dramatic scale.

Saturday, July 2, 2011

Announcing Accretionary Wedge #36

The subject of this Accretionary Wedge is:

"What do you regret leaving behind at a geological locality?"

In other words, what samples, specimens, or even photographs do you regret "not getting enough of"?

One mindset is that we should only pick up a few of whatever the item-of-interest is and leave some for others, but there are other considerations.  Sometimes outcrops get destroyed by construction...I have had that happen several times.  And weathering and erosion are always "attacking" fossils, minerals, etc..

So go back and revive those old memories of places that you may never have a chance to visit again.  It may inspire another geologist of two to pick up a few more specimens at a site - which of course can be shared along the way with other geologists or students if you find yourself in a classroom.  A well-timed gift to a student may be the genesis of a new scientist.

Ya'll have at it.  Please send your submissions by July 16th or so.  So that I might assemble and post the results by the following Monday.