Preliminary geologic map of Navajo Lake quadrangle, Kane and Iron counties, Utah

Abstract

Note: Most sedimentary bedrock in the map area is concealed by colluvium (Qc). The main purpose of the map is to show the distribution and structure of the bedrock. Thus, only a fraction of the colluvium was mapped where it is thickest. Colors of rocks, soils, alluvium, and weathering products were selected using a Munsell Soil Color chart and the Rock-Color Chart (Goddard and others, 1948). Sedimentary rock names follow the field classification of C. M. Gilbert (as illustrated in Williams and others, 1958, p. 270) Qal Alluvium (Holocene)~Low-level deposits on floodplains and in channels that consist of gravel and sand, silt, and clay mixed in varying proportions. At edges of floodplain, grades into colluvium (Qc) and fan alluvium (Qafl). Midway Valley floodplain deposits are dark brown (7.SYR 3/2) to strong brown (7.5YR 4/6); thick to thin-bedded; lenses of fine pebbles. The channel contains basalt and limestone gravel (2-50 cm in diameter) in a matrix of coarse sand, with subordinate light-gray (N7) ash-flow tuff of Isom Formation of latest Oligocene age (1-10 percent), white chalcedony (1-2 percent), and well rounded black chert pebbles (2-3 percent). The channel in Deer Valley is small or absent; floodplain alluvium is silty clay to clayey silt, yellowish red (5YR 5/8), slightly sandy, laminated to massive, and contains lenses, 2-40 cm thick, of angular limestone pebbles and some cobbles. Floodplain alluvium of Mill Creek (southwest quarter of quadrangle) is medium gray (N5), sandy and clayey silt to silty clay; thin interbeds of pebbles (limestone, basalt and sandstone); is terraced behind old beaver dams in places. Base covered; estimated thickness 2-5 m Qaf 1 AIIuvial-fan deposits (Holocene)~Fans around Navajo Lake: upper fan, chiefly clast-supported coarse gravel of limestone and minor sandstone and conglomerate containing some sandy matrix; middle to lower fan, pebbly sand to sandy pebble gravel, angular fine limestone pebbles, scarce small cobbles (8 cm in diameter); reddish yellow (5YR 6/6), poorly sorted, loamy quartz fine sand; distal fan is silty, slightly pebbly and clayey, very fine to coarse quartz and limestone sand, crudely stratified. Some hard layers 10-20 cm thick are cemented by calcium carbonate. East of dam, alluvium interfingers and grades to lake sediment (Qla) toward axis of valley; along shore it interfingers and grades to lake gravel (Qlg). At west end of Midway Valley, scarce ash-flow tuff (Isom Formation) gravel 20-80 cm in diameter occurs in moderate brown (5YR 4/4), silty fine sand matrix. On and south of plateau escarpment (Pink Cliffs), alluvium is dark-yellowish-brown (10YR 4/4) sand, silt, poorly to moderately well-sorted sand, pebbly sand, and silt, intermixed and interbedded. Thickness estimated to be 5-7 m at mid-fan Qat1 Alluvial-terrace deposits (Holocene)-In Midway Valley, sandy, poorly sorted, resistant gravel of basalt, ash-flow tuff of the Isom Formation, chalcedony, and sparse, round, chert and quartzite pebbles. Top of terrace is 1-2 m above stream channel. On Mill...

Geologic studies in the Basin and Range-Colorado Plateau transition in southeastern Nevada, southwestern Utah, and northwestern Arizona, 1995

“…We interpret the vent alignments as evidence that volcanism was controlled by the faults or by joints associated with the faults . Similar alignments are very common in the central part of the southern Markagunt Plateau, near Navajo Lake, and in the St. George Basin south of the study area (Thomas and Taylor, 1946;Anderson and Christenson , 1989;Moore and Nealey, 1993). In the central part of the Markagunt Plateau, where some alignments extend for as much as 12 km, vent alignments mostly trend north-northeasterly and northeasterly (Anderson and Christenson, 1989).…”

Drought-driven disturbance history characterizes a southern Rocky Mountain subalpine forest

“…Prior to the recent outbreak, Engelmann spruce was the oldest tree on every site except for the Bristlecone Pine Trail and Navajo Lake, where overstory Douglas-fir were similar in age (Table 1). The geologic substrate varies widely across the plateau owing to large intrusions of relatively young (Holocene) basalt lava flows, which occur within a matrix of much older (upper Cretaceous) formations composed primarily of sedimentary material, i.e., sandstones, mudstones, and limestones (Moore et al 2004).…”

Transformation of high-relief canyon topography by an ancient rock avalanche, Hop Valley, Zion National Park, Utah, USA

“…The rock avalanche dammed the North Fork Virgin River in Zion Canyon to create Sentinel Lake and blocked the Pine Creek tributary to generate a second small lake. The North Fork Virgin River basin is approximately 930 km 2 and drains portions of the Grand Staircase stratigraphy up to the Tertiary Claron Formation (Moore et al, 2004), as well as Quaternary volcanics (Biek, 2007c). The Pine Creek basin is approximately 90 km 2 and is dominated by the Navajo with lesser outcrops of the Temple Cap and Carmel formations (Doelling, 2008).…”