Landscape Evolution at an Active Plate Margin - Biological Science ...

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Figure 2-4. Computer-generated model for thermal cooling around a fumarolic vent. [D. R. Jessey] are oriented in a radial pattern. The lower Bishop Tuff (Lbt) is a strongly welded, massive tuff with irregularly developed vertical jointing. The Upper Bishop Tuff consists of pale pink, poorly welded, vitric pumice ash. It readily darkens to gray on weathered surfaces. The Ubt contains abundant pumice shards as well as phenocrysts of sanidine, quartz, and plagioclase. The Lower Bishop Tuff is more strongly welded with flattened and elongated pumice fragments common. (See if you can locate the contact as you walk down the DWP access road; in 2003 it was marked by Chinese writing!) Unweathered Lbt is pale red to gray and noticeably denser than the overlying Ubt. In all respects, the lower unit resembles a “textbook” ash flow welded tuff. Note from the table presented at the last stop that the two units are chemically very similar. The origin of the radial joint sets remains controversial. However, Mike Sheridan, while a graduate student at Stanford, undertook a computer simulation of gas flow in geothermal systems. He suggested (Sheridan, 1970) that each joint set represents the locus of fumarolic activity (Fig. 2-4). The radial jointing is similar to the heat flow pattern developed during cooling around a gas vent. The joints form normal to isothermal surfaces. If D. R. Jessey and R. E. Reynolds you look to the east, across the gorge you will see hummocky terrain with numerous surface bumps. Each “bump” would be the location of an inactive fumarole. Turn around and RETRACE to Hwy 395. 45.8 (0.2) TURN LEFT (south) on Gorge Road. 51.9 (6.1) TURN RIGHT toward Hwy 395. View at 10:00 to the west-southwest of lateral moraines at Pine Creek. 52.6 (0.7) Stop at Hwy 395. TURN RIGHT. Proceed north on Hwy 395 up Sherman Grade. 53.9 (1.3) Mono County Line. Volcanic tableland extends from here back to Middle Gorge. 57.9 (4.0) Vista Point on the right. The town of Bishop lies 13 miles to the southeast, Round Valley six miles to the south, and the escarpment of the Wheeler Crest to the southwest. The summit of Mt. Barcroft is 20 miles to the east in the White Mountains. 60.3 (2.4) Crossroad. 62.2 (1.9) Summit of Sherwin Grade, el. 7000 ft. 63.1 (0.9) Prepare for left turn. Watch for oncoming traffic. 63.3 (0.2) TURN LEFT and proceed east to the turnout on the left side of Lower Rock Creek Road. Figure 2-5. The “Big Pumice Cut” along Highway 395. The bouldery Sherwin Till is overlain by Bishop Tuff. The basal air-fall tuff is overlain by a much thicker ash-flow. An angular unconformity separates the units. Several prominent “clastic dikes” cut the tuff layers. [Photo by S. Lipshie, 1976] 34 2009 Desert Symposium
63.7 (0.4) PARK at turnout. STOP 2-4. Big Pumice Cut (N 37°33.27.4”; W 118°39’31.9”). Blackwelder (1931) first described the Sherwin till. This till is one of the oldest Pleistocene glacial deposits in the Sierra Nevada, exceeded in age only by the McGee till. Blackwelder believed that the Sherwin till was younger than the Bishop Tuff. However, Gilbert (1938) stated that the tuff is younger than the Sherwin till. Putnam (1960) studied the tilltuff at several localities including the Big Pumice Cut and concluded, as had Gilbert, that the Bishop tuff overlies the Sherwin till. However, Rinehart and Ross (1964) questioned whether the till that underlies the Bishop Tuff was really Sherwin till because of its apparent great age. Ash collected just above the till–tuff contact from the Big Pumice Cut was dated at about 710 ka (Dalrymple and others, 1965). That age was thought to be too old for the Sherwin glaciation, generally regarded as being equivalent to the Kansan and/or Illinoian glacial stages of North America. Sharp (1968) undertook a comprehensive study of relationships between the till and the tuff in the vicinity of the Sherwin Grade. He demonstrated conclusively that the Sherwin till is older than the Bishop Tuff and that the till exposed in the Big Pumice Cut is Sherwin till. A more recent 40 Ar/ 39 Ar date of 760 ka for the Bishop Tuff (Van den Bogaard and Schirnick, 1995) is the currently accepted age for the unit. Because the till appears to have undergone about 50,000 years of weathering prior to burial, it was thought be around 800 ka in age by Sharp and Glazner (1997). This suggests that it correlates with the Kansan glacial stage. When viewing the Big Pumice Cut (Fig. 2-5), note the contact between the boulder-laden till and the overlying, poorly indurated tuff. The basal 15 ft of the tuff is composed of air-fall material, while the overlying layer is an ash-flow. Within the tuff, layering of the air-fall ash is parallel to the Sherwin till erosional surface, whereas bedding in the ash-flow is horizontal. You should be able to see the angular unconformity between the two tuff units, although 2009 Desert Symposium Landscape evolutuion at an active plate margin: field trip recent weathering has greatly obscured that relationship. Also note, the tuff is cut by a series of vertical clastic dikes, perpendicular to layering, that extend into the till. The dikes, derived from gravel deposited on the tuff, consist of unconsolidated sand and gravel fining downward. Wahrhaftig (1965) suggested that the gravel originated as glacial outwash that slumped into fissures formed in the tuff. RETRACE to Hwy 395. 63.9 (0.2) Stop at 395. Watch for oncoming traffic! TURN LEFT and proceed north on 395. 58.6 (1.0) Pass Tom’s Place/Rock Creek Road. Owens River Gorge Road is on the right. Toms Place is named for Tom Yerby, who built a general store and cabins here in 1917. The town, once considered a backwater trailhead, has become the “hot” property of the eastern Sierra. Lots sell in the six figures, and million dollar vacation homes are not uncommon. 66.2 (2.3) Cross Crooked Creek Gorge. 66.6 (0.4) Continue past the turn to Hilton Creek and Crowley Lake on the right. Hilton creek is named for Richard Hilton, who had a dairy ranch along the creek in the 1870s. 67.9 (1.3) McGee Creek lateral moraines are to the Figure 2-6. Scarp of the Hilton Creek fault crossing a Tioga lateral moraine. McGee Creek flows to the north through the trees at the bottom of the photo. McGee Creek Road lies at the base of the moraine. [Source: Lipshie, S., 2001, Geologic guidebook to the Long Valley- Mono Craters Region of Eastern California, 2nd Edition: South Coast Geological Society Field Trip Guidebook] 35
Page 1 and 2: Landscape Evolution at an Active Pl
Page 3 and 4: Table of contents Landscape evoluti
Page 5 and 6: Evaluation of minor and trace eleme
Page 7 and 8: Landscape evolution at an active pl
Page 9 and 10: 25.3 (0.2) Continue past Osdick Rd.
Page 11 and 12: and Wesnousky, 1994). Reported rate
Page 13 and 14: into six units which range in age f
Page 15 and 16: Nevada & California railroad were u
Page 17 and 18: een built to meet the growing deman
Page 19 and 20: Figure 1-10. Offset drainages of Lo
Page 21 and 22: tary and metavolcanic units are lar
Page 23 and 24: Landscape evolutuion at an active p
Page 25 and 26: the Independence fault is dip-slip,
Page 27 and 28: Figure 1-18. Upper—view to the no
Page 29 and 30: 2009 Desert Symposium Landscape evo
Page 31 and 32: eruption of the Long Valley caldera
Page 33: Figure 2-2. Collapsed aqueduct pipe
Page 37 and 38: Sierra Nevada fault system has offs
Page 39 and 40: Landscape evolutuion at an active p
Page 41 and 42: (Cleveland, 1962). The rhyolite has
Page 43 and 44: ahead on the left. 95.6 (1.2) Stop
Page 45 and 46: ay. The big 40m dish is now used by
Page 47 and 48: cupied in 1865, and finally abandon
Page 49 and 50: Figure 3-6. Independence dikes. [S.
Page 51 and 52: which has significant concentration
Page 53 and 54: The Pliocene (Blancan NALMA) Coso F
Page 55 and 56: Current Research in the Pleistocene
Page 57 and 58: Quaternary data and references: A c
Page 59 and 60: and volume, p. 26-35. Smith, G. I.,
Page 61 and 62: Stolzite and jixianite from Darwin,
Page 63 and 64: (112) (Palache, et al., 1951). The
Page 65 and 66: ing gold and silver deposits. From
Page 67 and 68: the United States. Several small de
Page 69 and 70: at the base of the Lost Burro were
Page 71 and 72: silver-lead ore and is the one exce
Page 73 and 74: Significance of the Independence Di
Page 75 and 76: Independence Dike Swarm Figure 2: C
Page 77 and 78: 40 km of displacement was too low.
Page 79 and 80: dominant northwest strike. Dikes wi
Page 81 and 82: Moore, J.G., 1963, Geology of the M
Page 83 and 84: summarizes the formations you will
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The Perdido Formation conformably r
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note the spheroidal weathering patt
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Lower Cambrian-Precambrian stratigr
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lus. Six to ten species of echinode
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The Olancha Dunes, Owens Valley, Ca
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Triassic ammonoids from Union Wash,
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Archaeocyathids from Westgard Pass,
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Basaltic volcanism in the southern
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Basaltic volcanism in the southern
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oxene, whereas Pleistocene basalt i
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in much slower rates of displacemen
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Vegetation of the Owens Valley and
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cone and limber pine woodlands and
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Figure 21. The alpine zone of the W
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The rush from the Kern River mines
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The rush from the Kern River mnes i
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2009 Desert Symposium The rush from
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mining company; and A. K. Warner an
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chinery and the castings for a smel
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Advertisement for the Hobard and Re
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November 1864, a series of lines be
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When the geologist W. A. Goodyear v
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Montgomery City Alan Hensher, 593 C
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The Blue Chert Mine: an epithermal
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2009 Desert Symposium The Blue Cher
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2009 Desert Symposium The Blue Cher
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Tectonic implications of basaltic v
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The Goler Club Figure 2. Outcrop ma
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closest relatives were early Paleoc
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The Goler Club Figure 8. Goler Club
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prospecting, Baum wandered over to
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ejonian age (Thewissen 1990; Lofgre
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Fish Creek rhythmites and aperiodic
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We analyzed each of the three rhyth
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Figure 10. Threshold rhythmite prod
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Holocene slip rate and tectonic rol
Page 167 and 168:
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Figure 2. Camelops sp. (camel) meta
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moist, brush- and grass-covered, fr
Page 177 and 178:
Recent records of fossil fish from
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geal arches are similar to S. b. sn
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elatives seen in Pliocene and early
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Jennings, C.W. 1958, Geologic map o
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Competing mesquite and creosote dun
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Figure 9. Sheetwash area near the w
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The Oak Crrek mudflow of July 12, 2
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Photo 8. Deeply incised channel of
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than the north fork because of the
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mass contents of Gram negatives (sa
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to different uses. I do not suggest
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Geochronology and paleoenvironment
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Reproductive ecology of female Sono
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Garbage production is the other sid
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ties and preparation for use of som
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