Cedar Mountain Research Articles

A multidisciplinary study of the Lower Cretaceous Cedar Mountain Formation, Mussentuchit Wash, Utah: a determination of the paleoenvironment and paleoecology of the Eolambia caroljonesa dinosaur quarry

A quarry within the Cedar Mountain Formation in Mussentuchit Wash, Emery County, Utah, produced a fossil assemblage containing the remains of at least eight juvenile iguanodontid dinosaurs ( Eolambia caroljonesa). The Cedar Mountain Formation lies stratigraphically between the Tithonian–Berriasian (Upper Jurassic) Brushy Basin Member of the Morrison Formation and the Cenomanian (Upper Cretaceous) Dakota Formation. Detailed stratigraphic, sedimentological, geochronological, palynological, and paleontological data have been collected along a measured section at the site of the Cifelli #2 Eolambia caroljonesa Quarry. These data provide a chronostratigraphic and a biostratigraphic framework for the Cedar Mountain Formation and allow a detailed reconstruction of the paleoenvironment and the paleoecology of the local paleogeographic area from which E. caroljonesa have been recovered. Three 40Ar/ 39Ar ages ranging from 96.7 to 98.5 Ma have been obtained three stratigraphically distinct altered volcanic ash layers within the Mussentuchit Member, one of which passes through the E. caroljonesa quarry, that indicate that the quarry is latest Albian in age and that the stratigraphic boundary between the Mussentuchit Member of the Cedar Mountain Formation and the overlying Dakota Formation is at or near the Albian/Cenomanian boundary. Sedimentological and biostratigraphic data suggest that significant long-term and short-term climatic changes are recorded in the Cedar Mountain Formation. During deposition of the lower part of the formation, climatic conditions were warm and arid to semi-arid. During deposition of the upper part of the formation, conditions became more humid. The progressive change in climatic conditions was probably related to the transgression of the Mowry Sea from the north. Cyclic sedimentation in the Mussentuchit Member suggests high-frequency changes from wet to dry periods.

SEDIMENTOLOGY, STRATIGRAPHY, AND DEPOSITIONAL ENVIRONMENT OF THE CRYSTAL GEYSER DINOSAUR QUARRY, EAST-CENTRAL UTAH

Abstract The Crystal Geyser Dinosaur Quarry, near Green River, Utah, is located at the base of the Lower Cretaceous (Barremian) Yellow Cat Member of the Cedar Mountain Formation. The quarry preserves a nearly monospecific accumulation of a new basal therizinosauroid, Falcarius utahensis. We used field descriptions and petrographic analysis to determine the depositional environment and development of the quarry strata. Results of these analyses suggest that the quarry represents multiple episodes of bone accumulation buried by spring and overbank flood deposits. Evidence for these previously undescribed spring deposits includes calcite macroscopic structures within the quarry strata—such as pisolites and travertine fragments—and calcite micromorphologies—including radial-fibrous, feather, and scandulitic dendrite morphologies and tufa clasts. At least two episodes of bone incorporation are preserved in the quarry based on their stratigraphic position and lithologic associations. The unique depositional set...

Giant dinosaur eggs from the Tiantai basin, Zhejiang Province, China

Giant dinosaur eggs occur within the mid-Cretaceous Liangtoutang Formation of the Tiantai basin in Zhejiang Province of southeastern China. The 43 cm × 14.5 cm eggs represent the first discovery of Macroelongatoolithus xixiaensis specimens from the region. The eggshell exhibits variation in surface ornamentation and eggshell thickness, with smoother and thicker eggshell characteristic of the poles. The Tiantai eggs differ from the stratigraphically younger type specimen of Macroelongatoolithus xixiaensis from Henan Province in their mammillary to continuous layer ratio. Three new features potentially useful for phylogenetic analysis and previously unreported in Macroelongatoolithus and other eggs in the oofamily Elongatoolithidae include prismatic columns, tabular structure within the prisms, and "splaying" of the crystals in the upper mammillae that extend into the overlying continuous layer. Microstructural features of the two nearly complete eggs suggest that the specimens are referable to a potentially large theropod dinosaur. Paleogeographic distribution of these large theropod eggs includes the Late Cretaceous Zoumagang Formation of Henan Province and the mid-Cretaceous Liangtoutang Formation of Zhejiang Province in central and southeastern China and possibly the Lower Cretaceous Cedar Mountain Formation and mid-Cretaceous Dakota Formation of Utah, USA.

The pectoral girdle and forelimb of the primitive therizinosauroid Falcarius Utahensis (Theropoda, Maniraptora): analyzing evolutionary trends within Therizinosauroidea

ABSTRACT The recent discovery of a dense, paucispecific bonebed from the Early Cretaceous Cedar Mountain Formation, central Utah, has yielded new information on the morphology and evolution of therizinosaurs. Detailed description of the pectoral girdle and forelimb of Falcarius utahensis—the predominant taxon recovered from this site—provides the basis for a species-level, phylogenetic investigation of this enigmatic group. The analysis, consisting of 32 characters arrayed among 13 taxa, supports previous assertions that Falcarius represents the basal-most known member of the clade. The analysis further supports a monophyletic Therizinosauroidea on the basis of seven unambiguous synapomorphies of the pectoral girdle and forelimb. Contrary to previous hypotheses, analysis of the pectoral girdle and forelimb suggests that Therizinosauridae is more appropriately defined as a derived clade including Nothronychus, Erlicosaurus, Neimongosaurus, Therizinosaurus, and Segnosaurus. Equally strong support is recovered for a clade containing these five genera plus “Alectrosaurus” and Erliansaurus. The morphology of primitive therizinosauroids—characterized by Falcarius, Beipiaosaurus, and Alxasaurus—suggests that Early Cretaceous taxa already exhibited the beginnings of a trend toward increased robustness and altered range of motion of the pectoral girdle and forelimb. Derived therizinosaurs exhibit an amplification of these evolutionary trends as well as increased dorsal reach, increased wrist flexibility, and severe reduction in manual digit length. The functional reorganization of the pectoral girdle and forelimb throughout the evolutionary history of therizinosaurs can be reasonably attributed to a shift from obligatory predation to a novel paleoecological role that reached its pinnacle in derived Late Cretaceous members.

Natural fracture distributions in sinuous, channel-fill sandstones of the Cedar Mountain Formation, Utah

A set of regional natural fractures, present in the sandy to conglomeratic, fluvial, channel-fill deposits of the Cedar Mountain Formation (east-central Utah) has a consistent west-northwest strike regardless of the local axial orientations of the sinuous channels. The fracture-producing stresses were not significantly refracted by the mechanical-property contrast between the channel-fill sandstones and the encasing overbank mudstones. In addition, fracture spacing along the sinuous channel axes is relatively constant between one-half and one-third of the bed thickness for both large fractures that cut the full thickness of the channel deposits and for smaller fractures in the thinner, component beds. Fracture spacing was apparently not affected by the variations in stress amplification that commonly result from differently oriented stiff inclusions in a ductile matrix. Therefore, in the absence of other structures, fracture intensity and the orientation of fracture-related maximum horizontal permeability in sinuous elongated reservoirs will be relatively constant regardless of the orientation of the long axis of the reservoir. Whether maximum permeability trends along, oblique, or across such reservoirs, and the relative drainage efficiency of horizontal versus vertical wellbores drilled into them, will vary only with the local trend of the channel axis.

Dalton Wells: Geology and significance of debris-flow-hosted dinosaur bonebeds in the Cedar Mountain Formation (Lower Cretaceous) of eastern Utah, USA

The Lower Cretaceous Dalton Wells dinosaur locality, north of Moab, Utah, consists of a 2 m thick, stacked succession of four fossil-rich bonebeds with an estimated collective lateral extent of more than 4000 m 2. To date, 215 m 2 of the bonebeds have been excavated and more than 4200 vertebrate fossil field specimens have been collected. The site occurs at the base of the Yellow Cat Member of the Cedar Mountain Formation, and lies unconformably on Upper Jurassic strata of the Morrison Formation. The age of the assemblage is tentatively accepted as Barremian. Nine dinosaur taxa are recognized, making Dalton Wells one of the richest (abundance and diversity) Lower Cretaceous dinosaur localities in the world. The bonebeds are rare examples of fossiliferous subaerial debris flow deposits. At least four flows originated an undetermined distance up-slope from an Early Cretaceous site of dinosaur bone concentration and flowed through the site carrying bones short distances toward an adjacent area of lakes, ponds and wetlands. Host sediments most likely accumulated on the eastward-dipping slopes of a backbulge in a foreland basin. The overall depositional setting was alluvial–lacustrine in a warm-to-hot and seasonally wet-and-dry climate. The consistent expression and location of lacustrine facies in both the Brushy Basin Member of the Morrison Formation and the Yellow Cat Member of the Cedar Mountain Formation indicate that high rates of subsidence typified the Dalton Wells area both before and after the J–K transition, and further suggest that there was some form of long-term to episodic and localized influence on subsidence. The depositional slope required to generate debris flows may have been established by forebulge crustal flexure, but could also have been established or amplified by the high rates of subsidence that maintained the lacustrine paleoenvironments in the field area. Concretionary deposits in the Yellow Cat Member at Dalton Wells are diagenetic and apparently resulted from groundwater precipitation, likely enhanced by the presence of organics (bones) and lacustrine carbonates. The regional and cross-facies expression of calcretes in the Yellow Cat Member combined with the rarity of pedogenic indicators confirms that they are not paleosols. Mineral precipitation likely occurred as groundwater flow was established in response to foreland basin development. It remains unknown under what specific circumstances animals died and carcasses accumulated prior to being reworked by debris flows. However, the stratigraphic association of seasonally wet-and-dry facies throughout the Yellow Cat Member suggests that drought-induced mortality events were probably common. In a seasonally wet-and-dry environment, debris flows may have been triggered by intense rainfall or seismic events.

Chemical Composition of the Essential Oil of Micromeria libanotica Boiss., an Endemic Species of Lebanon

The essential oil obtained by steam distillation from Micromeria libanotica growing wild in the cedar mountains of Lebanon, was examined by GC and GC/MS. Twenty-five components, representing about 83% of the oil were identified. The major constituents of the oil were found to be the monoterpene ketones isomenthone (44.5%), pulegone (13.5%) and isopulegone (6.5%).

Hyperconcentrated Flows and Gastroliths: Sedimentology of Diamictites and Wackes of the Upper Cloverly Formation, Lower Cretaceous, Wyoming, U.S.A.

Abstract Diamictites and matrix-supported wackes of the upper Cloverly Formation (Lower Cretaceous) represent rivers laden with volcaniclastic sediment (hyperconcentrated flows). The Cloverly Formation of central Wyoming is dominantly fluvial, lacustrine, and playa deposits. The sediments accumulated east of the Cordilleran foredeep during the early stages of the Sevier orogeny. The diamictites and wackes are decimeters thick and stacked vertically, forming rock bodies up to 11 m thick. Pebbles and cobbles within the diamictites and wackes occur as isolated clasts or in poorly defined layers. Many such clasts exhibit some degree of polish. Clast lithologies can be correlated to rocks that were exposed in the mountain belt to the west. Provenance data are consistent with Early Cretaceous movement on the Meade–Laketown–Paris–Willard thrust system. The clay fraction of the diamictites and wackes is dominantly illite–smectite and smectite characteristic of altered volcanic ash. Diamictites and matrix-supported wackes lack primary sedimentary structures (e.g., cross-stratification) but do exhibit soft-sediment deformation features indicative of dewatering. Erosional bases and bedding geometries are indicative of channelized flow. The diamictites and matrix-supported wackes resemble debris-flow deposits. However, maintaining debris flows that behave as Bingham plastics on low depositional slopes 200–400 km from the mountain front is improbable. Rather, the diamictites and wackes represent hyperconcentrated flows. Deposition, either en masse by a Newtonian (or nearly Newtonian) flow that was turbulent throughout, or by progressive sedimentation from a stratified flow with a basal, incipient, granular mass flow overlain by a turbulent suspension is more consistent with the field data. Paleohydraulic calculations indicate that grain sizes up to small pebbles could have been transported in suspension, with larger clasts transported as bedload, consistent with sedimentological evidence. Much of the finer-grained suspended sediment was remobilized volcanic ash likely derived from the Idaho batholith to the west-northwest. The polished extraformational pebbles and cobbles, long regarded as dinosaur gastroliths (or stomach stones), are simply clasts associated with the hyperconcentrated-flow deposits. The polish exhibited by many of the clasts is attributable to transport in ash-laden flows. The occurrence of polished, extraformational stones in Cloverly diamictites and wackes may have implications for presumed gastroliths in other fluvial rocks of the western interior (e.g., the Cedar Mountain and Morrison formations).

A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah

Therizinosauroids are an enigmatic group of dinosaurs known mostly from the Cretaceous period of Asia, whose derived members are characterized by elongate necks, laterally expanded pelves, small, leaf-shaped teeth, edentulous rostra and mandibular symphyses that probably bore keratinized beaks. Although more than a dozen therizinosauroid taxa are known, their relationships within Dinosauria have remained controversial because of fragmentary remains and an unusual suite of characters. The recently discovered 'feathered' therizinosauroid Beipiaosaurus from the Early Cretaceous of China helped to clarify the theropod affinities of the group. However, Beipiaosaurus is also poorly represented. Here we describe a new, primitive therizinosauroid from an extensive paucispecific bonebed at the base of the Cedar Mountain Formation (Early Cretaceous) of east-central Utah. This new taxon represents the most complete and most basal therizinosauroid yet discovered. Phylogenetic analysis of coelurosaurian theropods incorporating this taxon places it at the base of the clade Therizinosauroiden, indicating that this species documents the earliest known stage in the poorly understood transition from carnivory to herbivory within Therizinosauroidea. The taxon provides the first documentation, to our knowledge, of therizinosauroids in North America during the Early Cretaceous.

Pattern and Rates of Faulting in the Central Nevada Seismic Belt, and Paleoseismic Evidence for Prior Beltlike Behavior

The central Nevada seismic belt (CNSB) is a concentration of historical (1915-1932-1954) surface faulting in the western Basin and Range province, forming a linear, nearly continuous 300-km-long rupture zone. Previous results are integrated in this study with new paleoseismic and exploratory trenching data from the historical zones to look for evidence of older, similar beltlike patterns or elevated slip rates that could indicate whether the CNSB is a zone of focused, long-term crustal strain. The data show that the continuous rupture belt produced by the seven earthquakes occurring between 1915 and 1954 is unique in the available paleoseismic record. At the 1954 Fairview Peak fault, the lack of prehistorical faulting in deposits containing the Wilson Creek bed 19 tephra eliminates the possibility of an identical seismic belt in the past 35.4 ka. Our studies also show that the faults have net slip rates ranging from a low of 0.09 mm/yr on the Fairview Peak fault to a high of 0.7 mm/yr on the 1932 Cedar Mountain fault. These are considered moderate to low rates that are similar to most late Quaternary faults in the western Basin and Range province. A space-time comparison shows that the paleoseismic histories for these multiple rupture zones are diverse, and the number and timing of events in each of the zones indicate that there is little evidence for older contemporaneous ruptures of these same faults. Based on these results we reach several conclusions regarding the longer term (≈Holocene) behavior of the CNSB. Although paleoseismic data preclude an older identical rupture belt among the historical zones, consideration of associated Holocene faults within the greater CNSB region indicates that several similar, but not identical, beltlike rupture patterns are plausible during the past 13 ka, although each requires seismic gaps in the along-strike pattern. Although long-term strain (represented by density of young faults) does appear to increase from east to west into the CNSB, the slip-rate data demonstrate that the CNSB is not a belt of concentrated or elevated crustal strain compared with areas that extend west to the Sierra Nevada. The increase in the distribution of Holocene fault activity from east to west into the CNSB is consistent with a marked increase in the 1992-2002 GPS velocity field at the latitude of the 1954 rupture sequence. However, a comparison of the geologic rates across the belt at this same latitude indicates that the extension rates (0.59-1.37 mm/yr) are systematically lower than both the campaign and continuous GPS rates (2.20-3.13 mm/yr) by factors of 2-5. These discrepancies may be due to postseismic strain, or to some form of off-fault deformation. We conclude that the results of our study of fault behavior in the CNSB best support the belt migration model proposed by Wallace (1987) for the western Basin and Range province in which temporal tectonic pulses are believed to migrate regionally, activating different beltlike combinations of late Quaternary faults in an as yet unknown pattern of migration.

Chapter 5: Marsupial Mammals from the Albian–Cenomanian (Early–Late Cretaceous) Boundary, Utah

The Mussentuchit local fauna, upper Cedar Mountain Formation (Cretaceous: Albian–Cenomanian), Utah, includes the geologically oldest marsupials: Kokopellia juddi, described previously, and three new taxa named herein. Adelodelphys muizoni, new genus and species, and Sinbadelphys schmidti, new genus and species, both unassignable to family, are among the smallest of Cretaceous marsupials; Pariadens mckennai, new species, tentatively assigned to Stagodontidae, is among the largest. The three are morphologically similar: they bear certain dental specializations of Marsupialia (e.g., presence of labial postcingulid and “twinning” of hypoconulid and entoconid on lower molars), but are plesiomorphic with respect to most or all Late Cretaceous marsupials in other features (e.g., relatively lingual position of conules, lack of stylar cusps C or D on upper molars). Compared to Late Cretaceous (Cenomanian– Maastrichtian) assemblages of North America, the marsupials of the Mussentuchit local fauna are rare and low in morphologic and taxonomic diversity. Biogeographic origin of Marsupialia and their antiquity in North America remain unknown. However, patterns of diversification and differentiation suggest that the taxa from the Cedar Mountain Formation lie near the base of North America's Cretaceous marsupial radiation.

Dinosaur Tracks from the Cedar Mountain Formation (Lower Cretaceous), Arches National Park, Utah

The seventh and largest known dinosaur tracksite from the Cedar Mountain Formation is reported from two important stratigraphic levels in the Ruby Ranch Member within the boundaries of Arches National Park. Previous reports of sites with a few isolated tracks are of limited utility in indicating the fauna represented by track makers. The Arches site reveals evidence of several theropod morphotypes, including a possible match for the coelurosaur Nedcolbertia and an apparently didactyl Utahraptor-like dromeosaurid. Sauropod tracks indicate a wide-gauge morphotype (cf. Brontopodus). Ornithischian tracks suggest the presence of an iguandontid-like ornithopod and a large ankylosaur. Dinosaur track diversity is high in comparison with other early Cretaceous vertebrate ichnofaunas, and it correlates well with faunal lists derived from skeletal remains, thus providing a convincing census of the known fauna.

Postseismic relaxation across the Central Nevada Seismic Belt

Two GPS geodetic surveys across the Basin and Range (BR) province of western North America have detected an anomalous compression east of the Central Nevada Seismic Belt (CNSB). The first network, installed by the U.S. Geological Survey along an east‐west trending transect across the BR at approximately 40°N, consisted of 63 monuments observed campaign style in 1992, 1996, and 1998. The second network, installed by the California Institute of Technology, consisted of 50 continuously operating GPS receivers, 18 of which were roughly along the same transect as the campaign survey. We have used a viscoelastic postseismic relaxation model of the four largest earthquakes in the CNSB (on the Pleasant Valley fault in 1915, the Cedar Mountain fault in 1932, and on the Fairview Peak and Dixie Valley faults in 1954) to interpret the geodetic velocities observed across the CNSB. A model of postseismic relaxation with a lower crustal Maxwell viscosity of 5–50 × 1018 Pa s can explain the apparent compression regardless of the assumed mantle viscosity. The geodetic velocities that we determined after removing the postseismic contribution indicate that within current GPS detection limits the BR is stable east of the CNSB and is undergoing rapid right‐lateral shear west of the CNSB.

A new teiid lizard from the Cedar Mountain Formation (Albian–Cenomanian boundary) of Utah

ABSTRACT A heretofore unknown teiid lizard, recovered from the Cedar Mountain Formation (Albian–Cenomanian boundary) of Emery County, Utah, is the oldest teiid that is represented by numerous specimens. This new taxon has a heterodont dentition with conical anterior teeth and transversely oriented bicuspid posterior teeth that are distinct from those of Peneteius (Late Cretaceous) and Teius and Dicrodon (Recent). It also shows ontogenetic variation in tooth shape, in which the posterior teeth become more massive and have more transversely expanded crowns, as the individual grows older. Further comparisons and analysis indicate (1) that North American Cretaceous Polyglyphano-dontinae (characterized by teeth with transversely-oriented crests) achieved their unusual dental specializations independently from those of analogous modern taxa; (2) that their transverse tooth-cresting resulted from addition of a medial cusp (rather than crown rotation, as previously hypothesized and which apparently is the case for living taxa); and (3) that the species from the Cedar Mountain Formation represents a sister-taxon to other North American poly-glyphanodontines Polyglyphanodon, Peneteius and presumably Paraglyphanodon and Dicothodon. The new taxon thus represents an example of the morphologically antecedent dental specializations that culminated in the strikingly specialized dentition of Polyglyphanodon sternbergi.

Lizards of the Mussentuchit Local Fauna (Albian–Cenomanian boundary) and comments on the evolution of the Cretaceous lizard fauna of North America

ABSTRACT A diverse fauna of lizards has been recovered from the Cedar Mountain Formation (Albian–Cenomanian boundary) of central Utah. These lizards are a component of the now recognized Mussentuchit local fauna and, like many of the other vertebrate groups within this fauna, show striking similarities to their North American Late Cretaceous (Campanian–Maastrichtian) counterparts. Unlike the Late Cretaceous lizard faunas, the lizards from the Mussentuchit local fauna also include at least one “paramacellodid,” a group common to Late Jurassic and Early Cretaceous lizard faunas of North America. Comparison with other Cretaceous lizard faunas from both North America and Asia indicates that the changes in the North American lizard fauna represented by the lizards of the Mussentuchit local fauna are likely the result of the introduction of taxa from Asia during the Early Cretaceous. Supposedly herbivorous taxa are found among the Polyglyphanodontine lizards from the Late Cretaceous of North American and Asia, but the general changes in the Cretaceous lizard fauna of North America cannot be convincingly shown to be linked to the concurrent angiosperm radiation. Later influxes of Asian lizard taxa prior to the Campanian may explain the relatively sudden appearance of additional groups of lizards in the early Campanian of North America. Whereas there is good evidence to support the hypothesis of an Asian influence on the Cretaceous lizard fauna of North America, there is insufficient evidence to determine what, if any, influence may have come from Europe or South America.

A new taxon of helodermatid-like lizard from the Albian–Cenomanian of Utah

ABSTRACT A new platynotan lizard, Primaderma nessovi, gen. et sp. nov., from the Mussentuchit Local Fauna, Cedar Mountain Formation (Albian–Cenomanian) of Utah is unique in having a premaxillary process of the maxilla that forms a vertical flange and fine serrations on anterior and posterior edges of the maxillary teeth. Primaderma is the oldest-known terrestrial platynotan and phylogenetic analysis indicates that it is a member of Monstersauria, a clade of helodermatid-like platynotans. The teeth of Primaderma show several derived platynotan characteristics, but do not possess venom grooves. The distribution of this trait in fossil taxa is reassessed. Although a North American origin of helodermatid-like platynotans is likely, it is possible that Primaderma represents another example of an Asian influence on the North American Cretaceous fauna. As with similar taxa, Primaderma was likely highly predaceous, presumably taking vertebrate prey and it appears that helodermatid-like lizards have changed very little since the Albian–Cenomanian.

New albanerpetontid amphibians from the albian to Coniacian of Utah, Usa—Bridging the gap

ABSTRACT Newly discovered fossils described herein from Utah, USA, help fill a sizeable gap in the Cretaceous record of the Albanerpetontidae and provide information on the evolution of the family during the latest Early–middle Late Cretaceous. The geologically oldest record of sympatry among albanerpetontids is in the Mussentuchit Member (latest Albian–earliest Cenomanian in age), Cedar Mountain Formation, where two indeterminate species are recognized based on jaws. The first species primitively resembles geologically older albanerpetontids in the structure of the premaxilla and documents the last appearance of this more primitive premaxillary pattern. The second species closely resembles the North American Campanian–Maastrichtian species Albanerpeton nexuosus in derived premaxillary features, and is the earliest record both of a subgeneric clade that includes all congeners, except A. arthridion, and of a less inclusive clade of Euramerican Upper Cretaceous–Miocene species having premaxillary synapomorphies that reinforced the snout. Albanerpeton cifellii, sp. nov. is named on a premaxilla having an inferred unique pattern of contact with the nasal. This new species is known only from the Smoky Hollow Member (late Turonian in age), Straight Cliffs Formation, and is the oldest member of a subgeneric clade of North American Upper Cretaceous species having a triangular or slit-shaped suprapalatal pit in the premaxilla. Indeterminate albanerpetontid bones are also reported from the above two units and the basal (early or middle Coniacian in age) John Henry Member, Straight Cliffs Formation.

A Light and Uncertain Hold: A History of the Sixty-sixth Ohio Volunteer Infantry (review)

364CIVIL WAR HISTORY general's adoption of a tactical offensive, while admirers of Longstreet will be subjected to Robert K. Krick's extremely harsh analysis of the First Corps commander's performance on July 2. The four new essays are welcome additions to the previous studies. Richard A. Sauers renders a fair and overdue assessment of George Meade's generalship on the final day. In contrast to Krick's essay on "Old Pete," Carol Reardon examines how soldiers in the First Corps, notably Pickett's Virginians, defended their commander's performance during the postwar years. Peter S. Carmichael, biographer ofWilliam Pegram, writes an excellent essay on why the Confederate artillery cannonade failed on July 3, and who was to blame. Finally, Gary M. Kross, a licensed battlefield guide at Gettysburg, counterbalances Carmichaers study with a portrait of Union artillery commander Henry J. Hunt and his conduct of the Federal batteries on the third day. Editor Gary W. Gallagher provides a fine introduction to the volume and a perceptive essay on Lee's decision to renew the offensive on July 2. Other contributors include A. Wilson Greene on Howard and the Eleventh Corps and Slocum and the Twelfth Corps, William Glenn Robertson on Sickles and the Third Corps, and D. Scott Hartwig on Caldwel's Second Corps division. Seven essays cover Confederate subjects, and six examine Union subjects. Although Three Days at Gettysburg offers only four new essays, the book is a fine contribution to Gettysburg historiography. The book is recommended, particularly for those who have not read the previous two volumes. Jeffry D. Wert Centre Hall, Pennsylvania A Light and Uncertain Hold: A History ofthe Sixty-sixth Ohio Volunteer Infantry . By David T. Thackery. (Kent, Ohio: Kent State University Press, 1999. Pp. xvi, 32 1. $35.00.) The late David T. Thackery, a native of Urbana, Ohio, who served as curator of local and family history at Chicago's Newberry Library, has created an accurate , detailed account of the previously unchronicled 66th Ohio Volunteer Infantry's participation in the Civil War. This scholarly work is more than a military history of the regiment recruited primarily in the west-central Ohio county ofChampaign. It is also a community history, offering glimpses into the family origins of county residents, antebellum political divisions and Underground Railroad activities as well as the postwar treatment and commemoration of its veterans. As the author rightly contends, "These men were also extensions of their communities" (xiii). In this regard, Thackery's work is similar in purpose to Kerry A. Trask's Fire Within: A Civil War narrativefrom Wisconsin. The 66th left Urbana, Ohio, in January 1862 under the command of Col. Charles Candy, who had previously served in the ist U.S. Infantry. The regiment initially formed a part of Lander's division of the Army of the Potomac. BOOK REVIEWS365 The 66th saw its first and costliest action at Port Republic, where Stonewall Jackson's forces inflicted a 50 percent casualty rate. A month later, its ranks were further depleted at Cedar Mountain. The 66th went on to fight at Antietam, Chancellorsville, and Gettysburg before its transfer to the western theater, where itjoined the Army of the Cumberland . Shortly after the Chattanooga campaign, the regiment faced reenlistment. Agonizing over his decision, Pvt. Joseph Diltz wrote, "Dam the enlisting again I am not so full ofWar as that" ( 1 80). "Veteranizing" won out with Diltz and the 66th. It became Ohio's first regiment to secure the necessary numbers to qualify as a veteran regiment. The 66th took part in Sherman's Atlanta campaign, the March to the Sea and through the Carolinas. At war's end, only two hundred of its original recruits remained with the regiment. In the final chapter, Thackery examines the postwar lives of some of the veterans and the ways in which they influenced their communities. Although many suffered lifelong disabilities, those soldiers who returned to Champaign County benefited from their veteran status. Not surprisingly, residents repaid their public debt by electing and appointing many of the regiment's veterans to public office. Utilizing newspaper accounts pension records, unpublished diaries and letters , county histories, and records of veterans' organizations, the author skillfully...

Surface faulting and paleoseismic history of the 1932 Cedar Mountain earthquake area, west-central Nevada, and implications for modern tectonics of the Walker Lane

The 1932 Cedar Mountain earthquake (M s 7.2) was one of the largest historical events in the Walker Lane region of western Nevada, and it produced a complicated strike-slip rupture pattern on multiple Quaternary faults distributed through three valleys. Primary, right-lateral surface ruptures occurred on north-striking faults in Monte Cristo Valley; small-scale lateral and normal offsets occurred in Stewart Valley; and secondary, normal faulting occurred on north-northeast–striking faults in the Gabbs Valley epicentral region. A reexamination of the surface ruptures provides new displacement and fault-zone data: maximum cumulative offset is estimated to be 2.7 m, and newly recognized faults extend the maximum width and end-to-end length of the rupture zone to 17 and 75 km, respectively. A detailed Quaternary allostratigraphic chronology based on regional alluvial-geomorphic relationships, tephrochronology, and radiocarbon dating provides a framework for interpreting the paleoseismic history of the fault zone. A late Wisconsinan alluvial-fan and piedmont unit containing a 32–36 ka tephra layer is a key stratigraphic datum for paleoseismic measurements. Exploratory trenching and radiocarbon dating of tectonic stratigraphy provide the first estimates for timing of late Quaternary faulting along the Cedar Mountain fault zone. Three trenches display evidence for six faulting events, including that in 1932, during the past 32–36 ka. Radiocarbon dating of organic soils interstratified with tectonically ponded silts establishes best-fit ages of the pre-1932 events at 4, 5, 12, 15, and 18 ka, each with ±2 ka uncertainties. On the basis of an estimated cumulative net slip of 6–12 m for the six faulting events, minimum and maximum late Quaternary slip rates are 0.2 and 0.7 mm/yr, respectively, and the preferred rate is 0.4–0.5 mm/yr. The average recurrence (interseismic) interval is 3600 yr. The relatively uniform thickness of the ponded deposits suggests that similar-size, characteristic rupture events may characterize late Quaternary slip on the zone. A comparison of event timing with the average late Quaternary recurrence interval indicates that slip has been largely regular (periodic) rather than temporally clustered. To account for the spatial separation of the primary surface faulting in Monte Cristo Valley from the epicenter and for a factor-of-two-to-three disparity between the instrumentally and geologically determined seismic moments associated with the earthquake, we hypothesize two alternative tectonic models containing undetected subevents. Either model would adequately account for the observed faulting on the basis of wrench-fault kinematics that may be associated with the Walker Lane. The 1932 Cedar Mountain earthquake is considered an important modern analogue for seismotectonic modeling and estimating seismic hazard in the Walker Lane region. In contrast to most other historical events in the Basin and Range province, the 1932 event did not occur along a major range-bounding fault, and no single, throughgoing basement structure can account for the observed rupture pattern. The 1932 faulting supports the concept that major earthquakes in the Basin and Range province can exhibit complicated distributive rupture patterns and that slip rate may not be a reliable criterion for modeling seismic hazard.

Therian Teeth of Unusual Design from the Mid-Cretaceous (Albian–Cenomanian) Cedar Mountain Formation of Utah

Enigmatic, abundant mammalian teeth from the medial Cretaceous of Utah are shown to belong to antemolar loci, based on dentulous jaw fragments; isolated teeth representing several upper premolar loci and the reconstructed c-p4 series are identified. Three species, differing in size and morphology, can be recognized. Morphological appropriateness, relative abundance, and distributional data indicate that the teeth can be referred with some confidence to the three symmetrodonts known from the Cedar Mountain Formation: Spalacolestes cretulablatta, S. inconcinnus, and Spalacotheridium noblei. If the specimens represent replacement or successional teeth, they are strikingly atypical for Mesozoic mammals, particularly in their low crowns and high degree of molarization at posterior loci. Jaw structure, wear pattern, and aspects of tooth morphology (e.g., proportions, degree of molarization, enamel thickness) favor the alternative hypothesis that these teeth are deciduous. Diphyodonty at all antemolar loci is generally assumed to represent the primitive condition for mammals, though fossil evidence is scant; some of the earliest mammals are known to undergo replacement only at the last premolar locus, with ontogenetic loss (rather than replacement) mesially. Available evidence suggests that, like the eupantothere Dryolestes, North American spalacotheriid symmetrodonts probably underwent single replacement at most or all premolar loci and that the deciduous series became progressively more molariform distally, particularly at the p3–4 loci. Assuming that these teeth are deciduous, their great abundance in the Cedar Mountain Formation (and, apparently, elsewhere in the Cretaceous of North America) suggests that North American spalacotheriids were subject to unusually high juvenile mortality rates or, more probably, that succession at premolar loci took place late in ontogeny, compared to other Mesozoic mammals.