At well 59 near the ICPP water of 1115 µS/cm (≈670+ mg/L TDS) enters the well from a permeable zone between 521 and 537 ft depth; the zone being 60 ft below the water level and water of 550 µS/cm. At the time of logging (9/14/93) the 1115µS/cm water was flowing down the well, mixing with less concentrated waters and exiting at 600 or 624-ft depth. Waste water disposed of down the injection well at ICPP until 1984 was estimated to have a C_s) of 1140 µS/cm, identical to the water detected in logging.

At well OW2, the highest C_s) water (760µS/cm) is in the upper 30 feet of the water column: water from two flow zones below have different chemistry with lower values of C_s. The Site 14 well and USGS 83 show uniform values throughout the water column. The water column in Site 14 is dominated by a downward flow of 50 gal/min probably entering between 475 and 500 ft depth and exiting near the bottom of the well at 700 ft depth.

Impeller flowmeter and precision temperature logging are used to define and quantify temperature variations and intrawell flows. At well 59 (depth=657 ft) and OW2 (depth=996 ft), are downward decreasing temperatures in the bottom zones of no flow, suggesting that major flow zones lie beneath the deepest parts of these wells.

Radiocarbon ages from a 2.7-meter auger hole at Ko Mae Mai in the Wiang Nong Lom swamp show that 0.5 meter of sediment accumulated in the past 218 years. This sediment rests on an older stiff clay. The stiff clay is Early Holocene in age. The age of this clay 1.05 meters below the sediment surface is 9,830 years. The stiff clay has hematite staining and a total organic carbon content of less than 0.6 per cent. This suggests that it has been sub-aerially exposed prior to inundation about 220 years ago.

Much of the sedimentary section at a site on the north edge of the swamp is older than Early Holocene and recent sediment there is no older than a few hundred years. A hiatus of deposition occurred when the site was dry. Time of inundation at this site does not agree with the legendary AD 460 earthquake and submergence of Yonok, but the age does allow that this site may have been dry and habitable in the interval from 1786 back to BC 9270. The sedimentation rate for clayey sediment at this site during the past 200 years is about 2.2 millimeters per year. This compares to similar high rates in the lake at Phayao in northern Thailand.

In northern Thailand the Mekong is mostly in a bedrock canyon, but shifting topography along the active strike-slip Mae Chan fault has formed the upstream 2-5-km wide floodplain at Chiang Saen, and downstream has diverted the river into a broad S-shaped loop in the otherwise straight course of the river. A 1.7-Ma basalt within the bedrock channel 45-km downstream of Chiang Saen indicates little vertical incision by the river. Satellite images show former channels in the Chiang Saen area, meander-point-bar scrolls (radii of curvature > 1.2 km), and floodplain edges as arcuate cuts of similar curvature into the saprolite-mantled bedrock hills These features indicate channel avulsion occurred by meander loop cutoff in the past. Brick Buddhist monuments of the 14th-16th Century were built upon the floodplain with meander features on the Thai and Laos side of the river, indicating that these meandering channel features and the broader floodplain are mostly older than 600 years.

During the Quaternary, an extensive system of mountain glaciers accumulated in the Pioneer and Boulder Mountains and flowed down valleys emanating from the ranges (Evenson and others, 1982, Pearce and others, 1988). An ice field several miles across accumulated in the Trail Creek Summit area and contributed ice to both the northeast-flowing Summit Creek glacier and to south-flowing Trail Creek glacier (fig. 2). Despite barroom talk in Sun Valley and Ketchum, we find no evidence that the resort towns or the Mt. Baldy ski hill were glaciated during the last ice ages. Rather, the glacier of closest approach was the Trail Creek glacier that advanced down valley to about elevation 1,950 m (6,400 ft), where Wilson Creek flows into Trail Creek, about 10 km (6 mi) northeast of the Sun Valley Inn.

The remnants of the two terminal moraines are best seen on the spur at the confluence of Wilson Creek and Trail Creek (fig. 3). From the road, facing northeast, the moraines appear as low ridges sloping 12º from the walls of Trail Creek Canyon down to Wilson Creek Canyon. Crest of the upper moraine stands 55 m higher than the lower moraine. The 12º crestal slope down into Wilson Creek, and low position in the valley indicate that this was the terminus of the two glacial advances. Furthermore, only outwash sand and gravel terraces occur below this area; no till or erratics are observed on the canyon walls down valley.

Day one of the trip will examine recent and Holocene fire-related deposits along the South Fork Payette River; day two will focus on alpine glaciation in the Sawtooth Mountains (fig. 1). A description of the scope, methods, results and interpretation of the South Fork Payette fire study is given below. Background information on late Pleistocene alpine glaciation in the eastern Sawtooth Mountains is presented with the material for day 2 of the trip.

The road log for day 1 of the trip begins at Banks, Idaho, and ends in Stanley, Idaho. Stop locations are shown on figure 2. At Stop 1, we will provide an introduction to interpretation of alluvial fan stratigraphic sections, and discuss the Boise Ridge fault. At Stops 2–4 (Hopkins Creek, Deadwood River, and Jughead creek), we will examine recent debrisflow deposits and Holocene alluvial fan stratigraphic sections. At Stop 5 (Helende Campground), we will look at a series of well-preserved Holocene and Pleistocene terraces and at Stop 6 (Canyon Creek), we will briefly inspect fire-related deposits in higher-elevation alluvial fan stratigraphic sections.

The road log for day 2 begins at Stanley, Idaho, and ends in Sun Valley, Idaho. Stop locations are shown on figure 2. Stop 1, at Redfish Lake, will focus on regional equilibrium line altitude reconstructions and on the general pattern of late Pleistocene glaciation on the eastern flank of the Sawtooth Mountains. Stop 2 will be at Pettit Lake, where we will examine the moraine sequence and discuss relative weathering criteria and moraine groupings. At Stop 3, near Alturas Lake, we will discuss lake sediment coring, moraine chronology, and implications for latest Pleistocene paleoclimatic inferences. Stop 4 will be a brief stop at Galena Summit for an overview of the Sawtooth Mountains and a discussion of ice accumulation patterns. The trip will end at a set of moraines in the Trail Creek valley, near Sun Valley, where we will examine moraine morphology and weathering rind data that constrain the moraine ages.

The mass of dry sediment (32.4 kg m⁻²), measured over a 0.32-km² area of the floodplain is relatively high compared to reports from European and North American river floods. Average wet sediment thickness over the area was 3.3 cm. Sediment thicker than 8 cm covered 16 per cent of the area, and sediment thicker than 4 cm covered 44 per cent of the area. High suspended-sediment concentration in the floodwater, flow to the floodplain through a gap in the levee afforded by the mouth of a tributary stream as well as flow over levees, and floodwater depths of 1.2m explain the relatively large amount of sediment in the measured area.

Grain-size analyses and examination of the flood layer showed about 15-cm thickness of massive fine-sandy silt on the levee within 15-m of the main channel, sediment thicker than 6 cm within 200m of the main channel containing a basal coarse silt, and massive clayey silt beyond 200 m. The massive clayey silt would not be discernable as a separate layer in section of similar deposits. The fine-sand content of the levee sediment and the basal coarse silt of sediment within 200m of the main channel are sedimentological features that may be useful in identifying flood layers in a stratigraphic section of floodplain deposits.