This study examines rock art sites containing scratched petroglyphs in the Bennett Hills, Idaho. Despite their research potential, scratched petroglyphs have received little attention in rock art research or literature. This study contributes valuable data to scratched rock art research and the corpus of rock art research in general. Two samples of ten scratched petroglyph sites were examined and recorded for a total of twenty petroglyph sites. Using formal and contextual research methods, multiple attributes of scratched petroglyphs are identified and analyzed. The formal qualities of scratched petroglyphs are examined to define the extent and to characterize the motif assemblage. Formal qualities were also studied to test hypotheses concerning the relationship between scratched and pecked petroglyph styles and associations between scratched petroglyphs and other archaeological phenomena. The contexts of scratched petroglyphs are studied on site and landscape scales to identify correlations with other archaeological phenomena and environments. The formal analyses revealed that there are more scratched petroglyphs in the Bennett Hills than records and literature currently indicate. Few site records document the presence of scratched petroglyphs, although as a result of this analysis it appears to be ubiquitous in the Bennett Hills. It is possible that scratched petroglyphs are under recorded in other locales as well, and that further investigations may identify a greater frequency of scratched petroglyphs throughout the Great Basin. Proper identification of scratched petroglyphs may alter how these properties are evaluated and in turn how they are managed. The Bennett Hills encompass a limited and unique assemblage of scratched petroglyph motifs that are dissimilar to petroglyphs manufactured using other techniques. This is significant in that it helps support the idea that scratched petroglyphs are distinct. Rather than just an alternative method to pecking, scratched petroglyphs serve a unique function that is different from and independent of pecked petroglyphs. Contextual analyses indicated that scratched petroglyphs are located in patterned and significant associations with artifacts, features, environments, and landscapes. The contextual analysis suggested that scratched rock art was produced in a public context in close proximity to subsistence related activities, perhaps in association with resource gathering events. There are various hypotheses that deal with the interaction between scratched and pecked petroglyph styles. Scratched petroglyphs occur both independent of and in association with other pecked petroglyph styles, although scratched petroglyphs do not commonly occur with any one pecked motif. When scratched and pecked petroglyph styles overlap scratched petroglyphs are always later than and superimposed over earlier pecked petroglyphs. Data was collected to test three hypotheses concerning the intention of association between scratched and pecked petroglyphs. It does not appear that scratched petroglyphs serve to obliterate earlier pecked petroglyphs or function as a sketch that would be pecked later. There is evidence that some scratched petroglyphs enhance earlier pecked petroglyphs however, this hypothesis cannot sufficiently describe the range of patterns and associations found in the Bennett Hills scratched petroglyph assemblage. Hypotheses suggesting associations between scratched rock art and other archaeological phenomena were also examined. The association between scratched petroglyphs and scratched stones is deserving of further research. It may also be too soon to dismiss the association between scratched petroglyphs and quartz. The examination of scratched petroglyphs in the Bennett Hills provides a unique insight into the minds of the makers of these petroglyphs, contributing valuable data our knowledge of the prehistoric peoples of the Bennett Hills and surrounding areas.

An integrated field, petrographic , structural , and geophysical analysis of the Panther Creek half -graben (PCHG), in east -central Idaho, was undertaken to determine its tectonic origin. Two competing theories as to the origin of the PCHG exist. One suggests that it formed as part of the TransChallis fault system (TCFS) , a system of northeast-trending normal faults, eruptive centers, and graben that formed in Middle Eocene time. The graben of this system are bounded by northeast-striking normal faults, and show evidence of syn-tectonic deposition of basin-filling volcanic strata. The other theory suggests that the PCHG may have evolved as a result of a post-Challis volcanic extension event (Late Eocene to Early Oligocene). Graben of this event are bounded by NNW-striking normal faults, and Challis volcanic strata are uniformly tilted; this evidence suggests post-volcanic basin formation. This study demonstrates that formation of the PCHG was mostly synchronous with volcanism and that there was very little post-volcanic deformation. Other conclusions of this research are 1) Rates of slip on basin-bounding faults were high, and slip was episodic. Slip occurred on both NE and NNWstriking faults, but more occurred on the NE-striking basin-bounding fault. This is consistent with the dominant NE strike of faults within the TCFS. 2) Most of the older volcanic units in the basin dip more steeply to the SE than overlying younger units , this is evidence for synvolcanic deposition . 3) There is significant hanging wall deformation in the form of folds and normal faults, particularly in the northern and southern portions of the basin . 4) Paleocurrents determined from provenance studies and imbricate fabric in exposed conglomerate beds indicate a flow direction largely to the northwest. This paleocurrent flow crosses the strike of the syn-extensional basin-filling units . 5) The composition of the clasts in the post-volcanic basin -fill deposits suggests that the thick volcanic units preserved in the basin never blanketed highlands NE, E, and SE of the basin and that the footwall of the basinbounding fault system was the main source of sediment in the basin. 6) The magnetic and bouguer gravity surveys indicate a sizable intrusion (most likely related to the nearby Casto pluton) beneath the west-central portions of the basin. The intrusion(s) may be responsible for east-plunging folds in the tuff of Castle Rock. 7) Work initiated during this study to determine the 40Ar/39Ar incremental-release mineral ages and the polarity of the tuff of Castle Rock and the tuff of Challis Creek will help determine the relationship between these two units and will precisely date basin development. However, it is clear that the basin was nearly fully formed by the end of Challis volcanism.

The southeastern Salmon basin (SB) of east-central Idaho is a complex east-dipping half graben containing four unconformity-bounded sequences of Tertiary volcanic, alluvial fan, lacustrine, and fluvial deposits. From oldest to youngest these are the Challis volcanic group, sedimentary rocks of Tendoy (new name), sedimentary rocks of Sacajaweja (new name), and Quaternary-Tertiary deposits . The thick sequence of volcanic rocks was deposited in a southeast-trending paleovalley . New mapping, cross-cutting relationships, 40Ar/39Ar age determinations, and angular unconformities show that the SB has experienced at least four episodes of extension, and that it lies in the core of an Eocene to Oligocene rift zone. T he largest episodes of extension in the SB were the second and third episodes of extension. These were responsible for the deposition of the sedimentary rocks of Tendoy and sedimentary rocks of Sacajaweja, respectively. Episode 2 occurred along the west southwest-dipping Agency Yearian fault, and can be attributed to gravitational collapse of the Sevier fold and thrust belt between the late middle Eocene and Oligocene (?). Several southwest-dipping low-angle normal faults were active during the third episode and may have been active into early Miocene time. The third episode of extension reflects continued gravitational collapse. Also active during episode 3 was the Salmon basin detachment fault, which is interpreted as a regional detachment based on its lateral extent and low dip angle (11°). Extensional folds are common in the southeastern Salmon basin and represent at least two generations of folds. Interference between northnortheast and southeast-trending folds locally produced dome and basin features. The folds are typically open to gentle, and have a maximum fold height of 2.2 km. Most of the folds are fault-bend folds, and some are associated with growth strata. The development of the Tendoy anticline and Pattee Creek syncline in the hanging wall of the Agency-Yearian fault produced two depositional basins during the deposition of the sedimentary rocks of Tendoy. Facies patterns and megabreccia deposits in the subbasins indicate that there was considerable topography along the margins of the subbasins .

The Kinnikinic Formation of central Idaho is a sedimentary unit consisting principally of orthoquartzite. From its maximum measured thickness of 2285 feet in the central Lemhi Range near Gilmore, Idaho, it thins westward to 376 feet at the type section and southward to 326 feet near Arco, Idaho. Northeast of the Lemhi Range it occurs only as erosional remnants, due to pre-Devonian erosion. Both the lower and upper contacts of the Kinnikinic Formation are disconformable. The Kinnikinic Formation is light colored, predominately fine to medium grained, thin to medium bedded, and largely cemented by silica overgrowths. Some metamorphic recrystallization has occurred locally. Although parallel laminae and structureless beds predominate within primarily parallel bedding, omikron-type (underwater dune) cross-laminae are locally abundant. The sediments are moderately sorted to well sorted and both positively and negatively skewed. Cumulative-frequency probability curves illustrate traction, "saltation," and "suspension" populations; some thin sections indicate two "saltation" populations. An open-marine, shallow-shelfal environment influenced by high-energy (tidal?) currents is postulated for deposition of the Kinnikinic Formation on the basis of the lithlogic uniformity, lateral extent, sedimentary structure, trace fossils, and paleogeographic setting. The Swan Peak Formation of southeastern Idaho and north-central Utah is divisible into a lower member of dark gray shale and quartz silitite, a middle member of brown orthoquartzite and light-colored shale, and an upper member of white orthoquartzite. Correlation of the white, fine- to medium-grained quartzite in the Raft River Range with the Ordovician Eureka Quartzite, considered probable by Compton (1972), is here accepted. The relatively thin nature of the Eureka Quartzite in this area reflects lesser sedimentation rates relative to areas farther south and/ or post-depositional erosion. The Dayley Creek Quartzite of Armstrong (1968) in the Albion Range is complexly faulted; as mapped, all or most of it probably is not correlative with the Kinnikinic Formation. Quartzites in the lower thrust plate of the Phi Kappa Formation in central Idaho are not environmental equivalents of the Kinnikinic Formation to the east, even though they apparently are approximately time equivalent (Churkin, 1963a, pp. 1612-1615). Middle Ordovician, shallow-shelfal orthoquartzit.es (Kinnikinic Formation, upper member of the Swan Peak Formation, Eureka Quartzite, and Mount Wilson Quartzite of southern Canada) are considered to be one originally continuous genetic unit, based on age determinations of overlying and underlying units, disconformable lower and upper contacts, close physical resemblances, and the high probability they were principally derived from the same source area, possibly Cambrian sandstones in the Peace River-Athabasca Arch area of northern Alberta, Canada. The shelfal environment of the Middle Ordovician Cordilleran miogeosyncline can be divided into at least five major, distinctly separated, basins of deposition: (1) Alberta-British Columbia Basin; (2) Central Idaho Basin; (3} Southeastern Idaho Basin (herein proposed); (4) Northeastern Nevada Basin; and (5) Ibex Basin. Anomalously high percentages of undulatory quartz grains in Middle Ordovician orthoquartzites of the Cordilleran miogeosynclinal shelf are highly suggestive of straining in situ and are probably related to post-depositional conditions ranging from purely tectonic to intricate combinations of tectonic and nontectonic events.