California Field Trip 2017

By Jackie Kendrick, Lisa Millar, David Burdon, Katie O’Dea, Ricardo Tomás, Stratos Delogkos, Nicola Kimber

Day 1 –  Western tip of Antelope Valley

Beginning with the San Andreas and Gawa faults. Overview to Fraser Mountain on a thrust caused by a transpressional regime. A look into Derek’s research of multiple landslide scarps from several time periods, caused by uplift but triggered by seismic activity. Landslide ~ 15000 yrs old with migrating gullies. Fans entrenched by the drainage. There is 440m of displacement along this section of the San Andreas fault. Slip can often be underestimated because slip also occurs on subsidiary faults. Slip varies along the fault. Top back-tilting of head block creates a depression on the surface. Ninac volcanics behind correlated to Pinnacles volcanics which have been displaced 240km. Bleich valley flats, landslide location showing delta top set beds river terraces and spillway. Displaying the previous river terrace heights/ spillway heights. Current work of MSc student, Mykola Sadler, to understand the depositional environment and correlate the multiple river terraces. For many of the MSc students, this was their first look at the tectonic regimes of California. A particular high-note was being shown around the study site by Mykola and providing suggestions for his project in the area. Beautiful drive to Shoshone (see below).

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Day 2 – Death Valley

Jubilee pass and the Amacosa chaos (Precambrian) first thing, with the morning led by Darrel Cowan from University of Washington. Down into Death Valley to see basaltic scoria cone which was offset. Death Valley has a 2mm NW spread every year. Talc mining in Crystal Spring where the dyke contacts the dolomite at 200ft. Moving west we examined the Frontal Fault Canyon, sedimentary rocks in a sheer canyon with steep detachment faults.

Then, we examined a fault with basement gneiss footwall with volcanic hanging wall. We were joined by a little friend too.

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Darrel gave us an insight into his most recent seismic survey across Death Valley, as well discussing the previous work in the Death Valley area that stretched back years.

Martini Glass Canyon, unfortunately does not house a bar.

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Then we went to Badwater – the lowest continental point in the USA (-85.5 m), possibly also one of the windiest points in the USA (!), occupied by gypsum salt flats.

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Due to the sandstorm in Death Valley we took a 240 mile detour on the route home to the Ubehebe Crater, the second windiest place in Death Valley. Some of the group ventured down into the crater for a closer look. The climb back up was tough, but it was well worth it for the view from the inside.

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We  stayed  at  SHEAR  centre  in  Shoshone  run  by  Darrel  Cowan.  An excellent resource. Good shower, lovely kitchen and the common area was well maintained despite the harsh conditions of the surrounding area. The kitchen was particularly useful as the town suffered a blackout when we arrived back and most of the participants had to cook their evening meals, which Darrel Cowan joined us for . We left our mark on the walls of the common area like many of the students and researchers who had stayed there before us. We were very happy to find some cold beers waiting for us in the fridge and felt it was only right to leave some beers for the next geologists to venture out into the desert. We hope this tradition continues!

Day 3 – Death Valley to Bishop

We started the day with a trip to Dante’s View, on the East side of Death Valley. Here we had a bird’s eye view of Death Valley basin, alluvial fans, the Badwater salt flats and basalt! Derek and Ricardo were on hand to explain any questions. Much appreciated.

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The view was so incredible that we just had to jump for joy (there were many failed attempts at taking this picture).

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At Twenty Mule Creek Canyon, surrounded by Quaternary alluvium around steeply dipping NE Tertiary sediments, we accidently came across a topless shoot.

Then, on to Zabriske Point overview of Twenty Mule Creek Canyon rocks.

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Mosquite Flat Sand dunes next to Stove Pipe Wells village have (the World’s only?) Star sand dunes created by four prevailing winds.

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Drove past Mt Whitney (highest peak in the contiguous USA) to look at the fault scarp of an earthquake from 1972 of magnitude 7.8. Looking at techniques to measure horizontal and vertical offset of fault scarps led to a long discussion on the sense of slip, it created more doubts than certainties and destroyed Phil’s attempts to keep us on time. Phil obviously knew there was a pool and a microbrewery waiting for us in Bishop!

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To get there we drove over the Saline Hills and past Owen’s Lake. Owen’s Lake was diverted (lost) by the building of the LA aqueduct in 1913. We also drove along …. Derek’s favourite road in California!

 Day 4 – Bishop to Long Valley to Lake Tahoe

A hot start at the Bishop Tuff 10 km north of Bishop. Air fall vs surge deposits from the 600 km3 760 ka eruption exposed beautifully in a quarry with breathtaking vies of the surrounding landscape.

McGee Creek to look at the Hilton Creek fault, a right oblique normal fault with 15-17 m slip. Went and played in the snow!

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Also a good viewpoint of the Long Valley resurgent dome and Lake Crowley, a moat-like lake caused by the South-dipping caldera floor. The resurgent dome uplifted by 500 m over a 10 km2  area, caused by rhyolite intrusion, expressed at the surface as dyke-fed-extrusions.

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From snow on towards Hot Creek, where we looked at the hot springs and the Bishop Tuff rhyolite in caldera infill, often with blocks of banded obsidian.

We all wanted a paddle but unfortunately these days the hot springs are too hot and too toxic for humans. Plenty of fish and cows about.

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A brief foray into Long Valley saw us drive past the Inyo domes (beautiful obsidian domes which will have to be saved for another trip!) and craters to our viewpoint over Mono Lake. Mono Lake is a saline soda lake with basaltic domes (<300 yrs old). Mark Twain famously described the lake in his 1872 book

‘Roughing it’ – “It is an unpretending expanse of grayish water, about a hundred miles in circumference, with two islands in its centre, mere upheavals of rent and scorched and blistered lava, snowed over with gray banks and drifts of pumice-stone and ashes, the winding sheet of the dead volcano, whose vast crater the lake has seized upon and occupied.”

Mono Lake is also the site of the iconic Pink Floyd “wish you were here” album cover (ok, inside-album- cover), but it’s still rather spectacular.

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Day 5 – San Andreas Fault, the long drive from Lake Tahoe to Yosemite

Due to winter snow the route from Lake Tahoe to Yosemite (usually a mere 4 hours) took us down the West side of the Sierra Navada, where we drove through the towns along the San Andreas Fault. Looking at road cuts (in the rain) down Highway 49, granite intrusions and metamorphosed sediments to serpentinite. Cars got separated, how is there still no signal through such large parts of the USA?! This meant some of the group arrived to Yosemite in darkness, though the earlier group were met with torrential rain. The tents provided just enough shelter to be quaint.

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Day 6 – Yosemite

A beautiful, although slightly wet, day in Yosemite following the valley-bottom trails (the top being snow- covered) to look at the Cretaceous granite diapirs (from 10km below surface 210-80 Ma) with mafic inclusions. Later uplifted and moulded by the Sierra Nevada, eroded into a glaciated valley littered with rock-fall deposits with “boulders” the size of houses. Impressive redwood trees populate the valley floor, amongst picturesque lakes, pools and streams (which proved to be entertaining obstacles following the monsoonal rain).

Much debate arose regarding how to use tree roots to date the rockfalls which led into a further debate as to how to protect the Yosemite Park investments from further rockfall movements. It was an amazing day. Even in torrential rain, Yosemite Park didn’t let anyone down.

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 Day 7 – Yosemite to San Francisco

A quick morning of waterfalls in the torrential rain, with a quick stop at El Capitan, to ensure everyone was good-and-damp for the long drive to San Francisco, where a 12-hour (incl. some sleep) whirlwind tour commenced – taking in an old cable car trip over Nob hill, the famous Lombard Street, sea lions at pier 39, sunset over the Golden Gate bridge, view of Alcatraz, dinner, Ghiradelli chocolate and cocktails for some!

There was a brief meeting with Keith Galvin, a former classmate of David Burdon who now works for the USGS. Unfortunately, Mr Burdon was so excited to see him, he hardly let him talk to the rest of the group until dinner!

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Day 8 – San francisco to Paso Robles via San Andreas fault and Parkfield

In what appeared to be the middle of nowhere we met with very enthusiastic and knowledgeable Prof. Wakabayashi to look at the Franciscan. Very shiny rocks. Kamakazee hammer action. Baby scorpion. Sunburnt arms galore. Several phases of metamorphism. Very complex!

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In the afternoon we stopped in the famous “town” of Parkfield, population 18 (plus at least as many dogs). A bridge just outside of the town directly crosses from one side of the San Andreas fault to the other, from the North American Plate to the Pacific Plate.

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Day 9 – Wallace Creek and on to Santa Barbara

Examining some offset gulleys along fault, and trying to decipher number of events indicated here gave a new perspective of the scale. Seeing Wallace Creek was very interesting from a tectonic movement point of view. As Derek would say, it’s text-book stuff. Lots of lizards in burrows too. Then farewell to Derek and a long drive, admiring the view, down the coastal highway 101 to Santa Barbara (nobody spotted the potential landslide risk posed by the road-cut, later demonstrated catastrophically in May!), for a last night of cocktails-galore.

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Day 10 – Santa Barbara to LAX and home

After a final eventful night in a brewery in Santa Barbara we departed in various batches, new friendships made, new knowledge gained, new stories to tell…

Thanks Derek and Phil! Thanks TSG!

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