Deformation associated with the San Andreas Fault along Highway 14, near Palmdale, California. The strata in the roadcut are lower to middle Pliocene gypsiferous, lacustrine rocks of the Anaverde Formation (a sag-pond deposit). Undeformed Pleistocene gravel unconformably overlies the Anaverde Formation.
I took part in a central California tectonics field trip a few weeks ago that the Association for Women Geoscientists (AWG) sponsored. Tanya Atwater and Art Sylvester, professors emeriti at the University of California Santa Barbara, Department of Earth Sciences, led the field trip. During the field trip, we made numerous stops between Los Angeles and Hollister at areas where the San Andreas Fault bounds the North American/Pacific plates. Interspersed with fault-specific localities, we explored associated geology such as turbidites around Point Lobos, marine terraces in the Morro Bay area, and pillow/flow basalt at Port San Luis. The final stop on the field trip was an overlook on Santa Barbara geology at La Cumbre Peak with Tanya’s explanation on the tectonic evolution of the Transverse Ranges. If you are not familiar with the tectonic history of this general area, go to Tanya’s web site (http://emvc.geol.ucsb.edu/) and download her visualizations on global/regional tectonics. There are also visualization downloads on ice-age earth and sea level changes, so treat yourself to some very worthwhile earth science information by downloading these visualizations, too.
The following photos are from what I think are field trip highlights, including a brief caption regarding the geology shown in each photo. More information on many of the photo localities can be found in “Roadside Geology of Southern California“, 2016, by Art Sylvester and Elizabeth Gans.
Pallet Creek trench site, near Juniper Creek, consists of sag pond deposits that developed atop the San Andreas fault during the past 2000 years. These strata now underlie a terrace adjacent to Pallet Creek. In the late 1970’s, Kerry Sieh pioneered the idea of trenching strata along a fault to determine age constraints on fault movement at this locality.On Tejon Pass, near Gorman, CA, it’s possible to place your feet on both the Pacific and the North American plates with little stretching effort. In this locality, the Pacific plate consists of quartz monzonite that is separated from the sandstone-silt strata of the North American plate by a zone of black-colored gouge developed along the San Andreas Fault.Wallace Creek, a drainage from the Tremblor Range of the North American plate, takes a right-angle bend where it crosses the San Andreas Fault and enters the Pacific plate, The current offset is approximately 100 yards. Check out the aerial photo at http://epod.usra.edu/blog/2006/12/aerial-photo-of-wallace-creek-and-san-andreas-fault.html for a great view of the offset.Cholame Creek near Parkfield, CA, delineates the trace of the San Andreas Fault. The plate boundary is well marked here and a similar sign is placed where one goes from the North American back to the Pacific plate.The Parkfield Experiment is an earthquake research project focused on the San Andreas Fault. The USGS and the State of California are the primary agencies involved in this project. For more info on the project, go to https://earthquake.usgs.gov/research/parkfield/index.php.Late Mesozoic Franciscan rocks along the Parkfield Grade are a chaotic assemblage of blocks of pillow basalt, chert, blue schist in a graywacke matrix. Note the scattered blocks of these rocks on the hillside and the blue schist block downslope in the foreground of this photo.Pinnacles National Park contains remnants of the approximately 23 million-year old Neenach Volcanics. This volcanic area developed atop the San Andreas Fault system, and some Neenach rocks are now displaced northward on the west side of the San Andreas Fault system about 320 km.In Old Town Hollister, CA, near Park Hill, a street curb is offset along the Calaveras fault.Creep is occurring along the Calaveras fault in Old Town Hollister.A building at the DeRose Vineyards near Hollister exhibits buckling due to movement along the San Andreas Fault.A concrete drain ditch at DeRose Vineyards shows about 1 meter offset along the San Andreas Fault.The San Juan Bautista mission west of Hollister is built adjacent to a straight hillside which is the San Andreas Fault scarp (located downslope from the white fence in the photo).The Weston Beach area at Point Lobos, Monterrey Peninsula, has turbidite strata (the Paleocene Carmello Formation) that are contained within a submarine canyon that is cut into Silurian granitodiorite.The Paleocene strata at Weston Beach are well know for their trace fossil assemblage. One of the more interesting, Hillichnus (shown in the central part of this photo), probably represents a feeding trace of a deposit-feeding bivalve.The Tertiary volcanic rocks on Pinnacles National Park’s west side are also part of the Neenach volcanics originally located further south near Lancaster, CA. As noted above, the volcanics in Pinnacles National Park have been displaced about 320 km northwards along the San Andreas Fault system.The Balconies Cave is a talus cave developed within the Tertiary volcanics on the west side of Pinnacles National Park.Morro Rock is part of the Morro Rock-Islay Hill Complex. The complex is a series of 27-23 million-year old volcanic plugs that stretch for 29 km southeast of Morro Rock.We stopped at the Montana de Oro State Park beach to see marine terraces (there are 6 terrace levels here). Unfortunately, because of the incoming marine layer, it was hard to see anything except an outcrop of the Miocene Monterrey Formation topped by Quaternary sediment.Pillow basalt (23 million years in age) occurs at Port San Luis.Pillow basalt is surrounded by shattered glass fragments at Port San Luis.Pillow basalt is topped by ropy basalt flows at Port San Luis.A view of Santa Barbara, CA, from La Cumbre Peak in the Transverse Ranges. La Cumbre Peak tops out at 3,997 feet within the Santa Ynez Mountains north of Santa Barbara, California. The peak consists of Eocene Matilija Sandstone. The existence of the Transverse Ranges is a topic that Tanya and her accompanying visualizations explain well. So once again – go to Tanya’s visualization web page and download her work on the Tranverse Ranges.We are ready for the concert at La Cumbre Peak!! Great way to end a fantastic field trip.
A few days ago I did the hike to Grinnell Glacier, one of the iconic glaciers in Glacier National Park. The glacier lies within the Swiftcurrent drainage area, in the northeastern part of the park. The hike, at least the way I did it, is about 11.6 miles round trip. It is possible to catch a boat ride at the Lake Josephine Boat Dock by the Many Glacier Hotel, which cuts the hike down to about 7.5 miles round trip. But – the first boat goes out at about 8.30 am, and as I didn’t want to wait around for it, I decided that adding on the extra miles for a fairly level stretch around Swiftcurrent Lake and Josephine Lake would be easy to do. It is an easy hike around the lakes and a very good warm-up for the rest of the climb to Grinnell Glacier. But – be aware that this area is known for grizzly bear activity as I found out when I met up with a grizzly on the trail. Because I’m writing about this encounter, it obviously ended OK, although I was glad I had bear spray readily available.
The glacier is named after George Bird Grinnell, who first explored this area during the summer of 1885. Because of bad weather, he did not actually get to the glacier during his 1885 travels. However, during the late fall of 1887, he was able to pack most of the way into the glacier by mules, and then hike the remaining distance by foot. Although he certainly was not the first person to see the glacier, the glacier does bear his name, presumably given it by a Lieutenant John H. Beacom of the United States Army, 3rd Infantry, who accompanied him on the 1887 trip to the glacier.
It’s fun to see ripple marks in the Proterozoic rocks that outcrop along the Grinnell Glacier trail (Grinnell Lake is in the photo’s background).
Back to the hike – after about a mile from the junction of the Swiftcurrent Lake Trail with the trail coming from the North Shore of Lake Josephine boat dock, Grinnell Lake comes into view. A little further along the trail one can see Grinnell Falls dropping several hundred feet down from the headwall behind Grinnell Lake.
Grinnell Falls drops several hundred feet down from the headwall to Grinnell Lake. The Salamander Glacier can be seen in the photo’s upper right-hand corner; Gem Glacier is in the upper left-hand corner of the photo.
And – even at this distance, Salamander and Gem glaciers pop into view in the distant cirque. The hike continues along beautiful alpine meadows and even through one waterfall that cascades down the cliff adjacent to the trail. There is a rest area with pit toilets right before hiking the final switchbacks that traverse the terminal moraine to the Grinnell Glacier Overlook.
The final part of the Grinnell Glacier trail traverses the glacier’s terminal moraine.Large boulder (Elrod’s Rock) in the Grinnell Glacier’s terminal moraine. Note the marmot atop the boulder for scale. The glacier’s terminus is now about a mile away from this boulder.
The three glaciers that once comprised the Grinnell Glacier occupy parts of a cirque developed along the area called the Garden Wall.
The cirque of the Grinnell, Salamander, and Gem glaciers.
Grinnell Glacier is still the largest of the three ice fields and covers about 152 acres. Unfortunately, this glacier is receding rapidly as the U.S.Geological Survey notes that from 1966 to 2005 it lost about 40% of its acreage. At about 5 acres, the hanging glacier called Gem Glacier, is the smallest named glacier in the park. It sits in the notch on the cliff face above the Grinnell Glacier. This glacier lost about 30 percent of its acreage from 1966 to 2005. The Salamander Glacier covers about 57 acres on a ledge off to the east side of the Grinnell Glacier. It apparently separated from the Grinnell Glacier sometime before 1929 and has undergone a 23% size reduction from 1966 to 2005.
For those interested in viewing photographs of the Grinnell Glacier from various times and viewpoints, the U.S. Geological Survey’s Repeat Photography Project has many archived photographs. This project is a documentation of glacial decline through photography and it is well worth perusing through their photo archives. Two of the earlier photographs are shown below – one from the original 1887 trek and a later view of the glacier from 1940 just to pique one’s interest.
1887 photograph of the Grinnell Glacier taken from footbridge (Lieutenant Beacom, Glacier NP. Public domain).Grinnell Glacier from trail 1900; Credit: F.E. Matthes, Glacier NP. Public domain.
Lion Mountain in the Gravelly Range of southwestern Montana. This area is federal land managed by the U.S. Forest Service.
A part of my recent geological field work includes working on high elevation Tertiary strata in the Gravelly Range, southwestern Montana. The Gravelly Range is located in southwest Montana, about 10 miles southwest of Ennis, Montana. For some background on this area and what my field work is about, see an older blog that I posted at Geopostings.
So – now that one field season is done and field data compiled, both my co-worker, Don Lofgren and myself have interpreted some of our data. We recently outlined our work at the Geological Society of America’s (GSA) Rocky Mountain section meeting in Calgary. Alberta. The abstract from our session is given below as well as the poster itself in both a jpeg format and as a link to our GSA presentation.
“Tertiary strata exposed in four high elevation areas in the south-central
Gravelly Range yield significant assemblages of Late Eocene to Oligocene
mammals. The thickest stratigraphic sections of Tertiary strata are in the
Lion Mountain-Black Butte area. The Lion Mountain section age is based
primarily on American Museum of Natural History collections; the lower
part of this section is Duchesnean-Chadronian (39-33 Ma) and the
uppermost beds are Whitneyan (32-31 Ma). Age of the basal part of the
Black Butte section is Duchesnean-Chadronian based on Harvard Museum of Comparative Zoology collections. Recent collections that include Miohippus indicate a probable Orellan age for uppermost exposures. The Tepee Mountain section is notable for abundant brontothere remains and is probably Duchesnean-Chadronian (approx. 39-33 Ma). The Rapamys site is the oldest vertebrate locality and is late Uintan to early Duchesnean (42-38 Ma) based on recently recovered specimens of Rapamys, Protoreodon, and Lycophocyon.
The Tertiary strata in this part of the Gravelly Range include fluvial, aeolian, and tufa deposits that are most likely mainly associated with localized Oligocene volcanism. The Lion Mountain section is about 270 meters in thickness; the lower half of the section is largely aeolian, with fluvial units comprising much of the upper section. Based upon age data, the 140 meter Black Butte section correlates to the lower 50-70 meters of the Lion Mountain section. The basal 20 meters of the Black Butte section contain some fluvial features, but much of the remaining section is largely aeolian in origin. Paleosols and extensive burrowing also occur within the Black Butte section. Stratigraphic section thickness decreases rapidly away from the Black Butte-Lion Mountain area, with section thicknesses of about 20 meters for the largely aeolian Rapamys and Tepee Mountain sections. Tufa deposits are located along the west-central edge of the Gravelly Range where they are associated with previously mapped thrust faults. Leaf imprint assemblages of Eocene-Miocene age are contained within these tufas. Strata previously mapped as Upper Cretaceous-Paleocene Beaverhead Formation are now variously reassigned to the lower Cretaceous Kootenai Formation, southwestern Montana Cenozoic Sequence 2, and diverse Quaternary units.” From: Abstract from Geological Society of America Abstracts with Programs. Vol. 49, No. 5 doi: 10.1130/abs/2017RM-293156.
The poster presented at the 2017 Rocky Mountain GSA is available below as a jpeg and at GSA as a pdf.
The Canadian Rockies to Alberta Badlands geology guidebook is published by the Association for Women Geoscientists.
The Association for Women Geoscientists (AWG) published their first geology field trip guidebook in late 2016 and it is now available for sale to the general public. This guideboook is a collection of geology road logs, associated geological information, and local cultural history of areas within the Canadian Rockies and the Alberta Badlands. The following text is a brief summary of the guidebook:
“TECTONICS, CLIMATE CHANGE AND EVOLUTION – SOUTHERN CANADIAN CORDILLERA: Road Log and Accompanying Narratives From: Calgary – Lake Louise – Icefields – Field – Revelstoke – Fernie -Dinosaur Provincial Park – Calgary”, published by the Association for Women Geoscientists, 2016.
This field trip guidebook is written by Katherine J.E. Boggs and Debra L. Hanneman, and edited by Janet Wert Crampton and Stephanie Yager. It is the AWG’s first fully published field trip guidebook and is a field-tested guide from their two-week 2014 field trip through the Canadian Rockies and Alberta’s Badlands area.
The guidebook is a 209-page geology tour through many of the well-known parts of the Alberta Canadian Rockies, including the Front and Main Ranges of the Canadian Rockies and the Columbia Icefields. The Burgess Shale’s Walcott Quarry, the Okanagan Valley vineyards, and the Rocky Mountain Trench are trip highlights for geo-tours in British Columbia. The field trip guidebook ends with a geology tour of the Crowsnest Pass area on the British Columbia/Alberta border, and with field stops in Alberta’s Dinosaur Provincial Park and at the Royal Tyrrell Museum, Drumheller, Alberta.
The field guide is printed on double-sided 8.5″ x 11″ pages with the guide cover on 100 lb paper and the text on 80 lb paper. It has black wire-o binding and a clear acetate front and a black acetate backing for improved field durability. The guidebook’s cost is $55 USD (which includes shipping), and can be purchased at the AWG online store or by phoning the AWG main office at 303-412-6219.
Lion Mountain in the Gravelly Range of southwestern Montana. This area is federal land managed by the U.S. Forest Service.
I love living in Montana, but some days are just better than other days. This is one of those “better” days. This morning I checked my media feeds to learn that more than forty Montana writers have come together to write about their support for protecting our public lands and to also endorse Montana’s Special Congressional election Democrat candidate Rob Quist’s position on this issue.
The push for the transfer/sale of public lands, particularly federal public lands, has reared its ugly head again in many forms across the western U.S.A.. This is an issue that needs to be met head on by all of us who value our public lands.
The 24-page tabloid writers’ anthology will be part of three Montana state newspapers this Sunday. Copies will also be handed out at this weekend’s Quist events with Sen. Bernie Sanders in Missoula and Bozeman. The anthology is also available as a pdf download at the “We Take Our Stand” website.
A nodosaur, approximately 112-110 million years old, was found in the Alberta oil sands March 21, 2011. The dinosaur is basically a mummy, with fossilized skin and gut contents intact. Luckily, the heavy-equipment operator and his supervisor knew that what was being unearthed at Suncor’s Millennium Mine that amazing day in March was unusual. It was so remarkable a find that they notified the Royal Tyrrell Museum in Drumheller, Alberta, and museum workers quickly came up to the mine to collect it. After 6 years and over 7,000 hours of preparation work, the dinosaur is now on exhibit at the Royal Tyrell Museum in the newly opened Grounds For Discovery exhibit. For more information on the discovery, check out National Geographic’s article – The Amazing Dinosaur Found (Accidentally) by Miners in Canada.
Scientists from the Universities of Bristol and Cambridge used a drone to video an eruption of one of Guatemala’s active stratovolcanoes, Volcan de Fuego. The volcano is part of the Central America volcano arc and is one of three large stratovolcanoes close to Guatemala’s former capital, Antigua. The drone flew 3,700 m over Volcan de Fuego to get the video footage.
I took a break from writing a paper on Tertiary volcanic tuffs in southwestern Montana a few days ago to go on our yearly steelhead fishing trip on the South Fork of the Clearwater River in Idaho. Steelhead are amazing fish in that they are ocean-going rainbow trout that spend two years in the ocean, and then swim back into Idaho rivers like the Clearwater, Snake, and Salmon. Eventually the steelhead reach these rivers’ upper stretches for their spawning grounds. On the South Fork, steelheads are considered as “B-runs”, which are a mix of both native and hatchery fish.
Extremely high water levels marked this year’s steelhead fishing trip. Rocks of a Jurassic-Cretaceous felsic pluton outcrop along the South Fork’s edge.Steelhead are ocean -going rainbow trout that eventually migrate into the upper reaches of Idaho rivers such as the Clearwater, Snake and Salmon rivers, to spawn.
This year’s fishing adventure was marked by extremely high water levels. We usually fish at an area called the Hog Hole, a part of the South Fork that is armored by large boulders – and as an Idaho Fish and Game person told me – is an impressive velocity barrier to upstream fish migration. Fisherman typically occupy many large boulders that are scattered across the river at this location. That wasn’t possible during our fishing trip as the high water limited us to standing on only the rocks along the river’s banks.
The other impressive part of this annual fishing trip is that it takes place basically along the Western Idaho Suture Zone (WISZ). The WISZ, as noted by Fleck and Criss (2004)…
represents the boundary between crust overlying Proterozoic North American lithosphere and Late Paleozoic and Mesozoic intraoceanic crust accreted during Cretaceous time (Fleck and Criss, 2004).
Map showing composite Blue Mountains terrane and geology of the suture zone and adjacent North American terranes (from Idaho Digital Atlas).
The Digital Atlas of Idaho gives a good overview of the WISZ and accreted terrains. For the South Fork of the Clearwater, the Digital Atlas also breaks down the Idaho geological map by county, with the stretch that we fish lying in Idaho County. According to the Idaho County geological map, the Hog Hole sits on the west side of the suture, in accreted terranes that are partially covered by Tertiary Columbia River basalts (17.5 million to 6 million years in age) and intruded by Jurassic to Cretaceous (160 million to 120 million years in age) felsic plutonic rocks. Glacial sediments overlie these older rocks, particularly in the upper part of the South Fork drainage. The juxtaposing of all the varied geology does add another level of enthusiasm for the annual fishing expedition!
A Columbia River basalt flow underlain by a red-colored paleosol,. The basalt-paleosol outcrop is alongside State Highway 13, on the grade up from the South Fork to Grangeville, Idaho.Slumps were ubiquitous along both the Clearwater and the South Fork of the Clearwater rivers because of the large snowpack and the recent rain.
A very large crack is forming in the Larsen C Ice Shelf on the Antarctic Peninsula. The crack is up to 1,500 feet wide and will most likely generate one of the largest icebergs on record. Only 6.4 miles of ice are keeping the ice sheet from calving off an iceberg that is basically the size of Delaware. Researchers who have been studying the ice melt (Project MIDAS) estimate that although the exact timing of the calving event in unclear, it could occur easily within the next few months. In fact, scientists noted that the crack spread another approximately six miles during the second half of December 2016. From January 1st to January 19th, the crack expanded again, and now only 6.4 miles of unbroken ice remains. Once the calving event occurs, scientists are concerned that it will destabilize the Larsen C ice sheet to the point of its disintegration.
The current location of the rift on Larsen C, as of January 19, 2017. Labels highlight significant jumps. Tip positions are derived from Landsat (USGS) and Sentinel-1 InSAR (ESA) data. Background image blends BEDMAP2 Elevation (BAS) with MODIS MOA2009 Image mosaic (NSIDC). Other data from SCAR ADD and OSM (update on graphic from Freedman, based on Project MIDAS data).
British Antarctic Survey (BAS) recently captured the following video footage of the immense crack in the Larsen C Ice Shelf:
Geoawesomeness got my attention today by featuring a You Tube video done by Vox folks a few months ago. The Vox video points out that basically all world maps are wrong in how projections of land masses are variously shown. Aleks Buczkowski from Geoawesomeness gave a lead-in to the Vox video in his posting on it by saying:
Projecting a round surface of the Earth on a flat surface is not an easy task. Scientists are trying to find an optimal way to do it for centuries. In fact the most common map projection that we use almost everyday in Google Maps and other mapping services, has been introduced in 1569 by Gerardus Mercator.
The video from Vox does help to explain the intricacies of map projections and is really worth watching:
