June 2015 Field Trip Log
Mile
MP
Stop
Feature
Day 1 (Saturday)
0.0
11.4
13.6
15.1
16.1
17.6
19.5
26.1
28.0
28.8
31.1
2.6
3.1
3.2
5.2
5.3
6.4
9.0
When Highway 55 starts to drop steeply after the road to Brundage,
the outcrops are part of the Little Goose Creek Complex along the
suture zone of continental and island arc rocks. We won't stop here
now, but on the way back to Boise there is a good pullout on the
right and you can walk up the road (carefully) to look at the
formation. (May not be possible due to road construction)
156
New
55 – 95 Jct. Re-zero odometers here.
Meadows Mile Posts change to 161 on US 95 at New Meadows
171.8
1
Smoky Boulder Creek - Palagonite basalt outcrop and
basalt.pillows - this basalt flowed into a lake, causing the altered
appearance (brown).
173.4
2
Hazard Creek gneiss - metamorphic volcanics
174.5
3
Mafic Hazard Creek gneiss - metamorphic sediments and siltstones
176.8
4
Basal entablature in private quarry - like it was flowing when it
formed wavy columns.This is the lowest flow of the Columbia
River Basalts - the Imnaha Basalt.
178
5
Imnaha Basalt with Zeolites
180.9
Not a stop, but look at strange columnar basalt outcrop on left, with
vertical to horizontal columns. You could stop here on way back
south with safe parking
187.5
6
Rattlesnake fishing area. This is the Hat Creek Landslide area. The
schists in this area make a talc when they weather and are thus very
slippery, leading to the landslide.
188
7
Ultra Mafic Lens of talc and serpentine or quartzite in a shear zone.
188.9
8
Rest Area. Squaw Creek Schist on R side of road. This is the
dominant unit from here up to Riggins and out along the first part
of the Salmon River Road route.
191.1
Rapid
Begin Side Trip, Zero Odometer
River Rd.
9
Park in Rapid River Trailhead. There is an optional hike of about
0.25 miles (0.5 miles round trip) to an outcrop of marble.
10
Quaternary river gravels over phyllite of Lucile Slate (but may be
sheared Squaw Creek schist.
11
Talc schist pod on contact of Lucile Slate and Lightning Creek
Schist.
12
Lightning Creek Schist - a greenschist.
191.1
Junction Highway 95. Do not reset odometer
192.4
Not a stop, but a good view of alluvial fan with layering in cut
across Little Salmon River.
195
Riggins
Day 2 (Sunday)
0.0
0.05
0.4
-
Riggins
1
2
4.2
-
3
6.2
-
4
9.0
13.5
5
-
6
1.9
197.3
7
2.1
197.5
8
5.4
200.1
9
27.0
10
8.1
203.1
11
8.9
203.9
12
10.1
205
15.5
210.1
15.9
210.7
13
Little Salmon River Bridge. Zero Odometer
Massive Squaw Creek schist just across the bridge
Massive Salmon River gravels with imbrication (they are tilted
downstream). Also from this stop, looking back to the west, there is
a ziz-zag fold in the Squaw Creek Schist visible on the hillside.
Berg Creek amphibolite; this is a hornblende and garnet
metasediment.
Garnet-bearing Lightning Creek schist Walk back to beginning of
parking area and then across the road. The garnets have light halos.
There is a small "slickenslide" evident in the schist, indicating fault
movement.
Riggins Hot Springs across the river. The outcrop here is the
beginning of the shear zone of the accreted terranes. There are also
granite and pegmatite intrusions in the gneissic rocks.
Here, just across the Manning Bridge, we have crossed the shear
zone and are in the Crevice Pluton of the archaic North American
craton.
Junction Hwy. 95. Lunch in Riggins
Zero odometer leaving lunch spot.
South Goff Bridge. This is a dramatic location for hornblende
crystals in the schist.
North Goff Bridge. Park just beyond bridge on left. This is a
complex sequence of ultramafic rocks from Squaw Creek Schist to
light talc carbonates, to antigorite serpentinite (see diagram).
Park on left. Lightning Creek schist with "agglomerate" clasts of
green schist in big boulders on side of parking area.
Park at North end of fruit stand lot and walk north to Fiddle Creek
Schist - this is a "white" schist that is not very "schisty."
Martin Bridge Limestone - pull out on right onto old highway and
turn left to the outcrop. The limestone is really metamorphosed into
marble.
Rest Stop and Lucile slate. The outcrop is across the road and
slightly north of the rest stop, but there is no parking there - walk
from the rest stop parking area.
Not a stop, but look at Gold Mine in river gravels on Right - a
death trap!
Steelhead Inn, site of 1998 landslide, evident from "stone catcher"
fencing on right. No place to stop here but we can look back from
the Long Gulch access road.
Turn off on Long Gulch Access Road. Long Gulch landslide is
visible looking back south. Drive a little farther to outhouse, Mt.
Mazama ash visible here as a white band in the road cut across the
road. We turn around after this stop.