The present study was a systematic investigation of hierarchical skill sequences in the beginning reading domain. The hierarchies included skills from the traditional approach to reading which reflect bottom-up processing and skills from the conceptual area of print awareness which reflect top-down processing. Researchers supporting the bottom-up approach view reading as a process in which the child extracts information from the text to gain knowledge of the print. The bottom-up processes examined were in the areas of letter recognition and letter naming, and identification of letter sounds and phonemes. The top-down processing approach views reading as a task in which the child brings his/her past experiences and knowledge about the world to gain information about print. The top-down processes examined were in the areas of print identification, inferring a word in context, and print directionality rules. Hierarchical skill sequences were developed within each of the specific areas reflecting the top-down and bottom-up processing theories. Items were developed to reflect the skill sequences based on the cognitive processes that are necessary for correct performance. This involved varying the task demands imposing various requirements of cognitive processing. The data were from 13,189 Head Start children ranging from 3 to 6 years of age. Latent trait models were constructed to reflect the viii ix hypothesized skill sequences by allowing the aj (discrimination) and bj (difficulty) parameters to be free to vary or by constraining them to be equal to other parameters. To arrive at a preferred model, each latent trait model that represented a hypothesized skill sequence was statistically compared against alternative latent trait models. The results from the present investigation supported the hierarchical skill sequences reflecting skills within the traditional area of reading. However, some of the skill sequences from the conceptual area of print awareness were not clearly supported. While the results provide a deeper understanding of beginning reading skill sequences reflecting top-down and bottom-up processing theories, future research is needed to delineate the specific skills which promote later reading ability once the child is in formal reading instruction.

The Paleocene and early to middle Eocene Family Phenacodontidae includes three species--Tetraclaenodon puercensis, Phenacodus vortmani, and P. primaevus--with available postcranial material for an investigation of postural and locomotor capabilities. The details of bone and joint morphology are compared within the phenacodontids and with several extant analogues whose postural and locomotor capabilities and morphological correlates are known better. Several aspects of the postcranial morphology of the phenacodontids, especially P. vortmani and P. primaevus, suggest cursorial capabilities. The anterior thoracic vertebral column has limited flexibility dorsoventrally and mediolaterally, but the articular surfaces in the lumbar section, especially in the larger P. primaevus, tend to allow dorsoventral movement while restricting mediolateral movement, thus potentially adding to total stride length. The digitigrade limb posture, again especially developed in P. vortmani and P. primaevus, adds to limb length and stride length. Several features of the joints in the forelimb and hindlimb restrict motion to the parasagittal plane or enhance thrust against the ground in the parasagittal pIane, thus contributing to forward motion. The curvatures of the glenoid fossa and the humeral head enhance flexion and extension and restrict abduction. The mediolateral width and shapes of the articular surfaces in the elbow joint prevent supination. The flexor hinge in the wrist allows a powerful thrust against the ground during push-off. The keels in the distal metapodials maintain that thrust in the parasagittal plane. In the hindlimb, the high greater trochanter and the third trochanter increase the mechanical advantage of some extensors of the femur. The deep patellar groove suggests strong extension at the knee. Similarly, the deep grooves and distinct condyles of the distal tibia and dorsal surface of the astragalus, along with the relatively long calcaneal tuberosity, suggest powerful flexion at the ankle joint and confine motion at the upper ankle joint to flexion and extension. The phenacodontids and especially Phenacodus vortmani and P. primaevus were good runners, particularly compared with their Paleocene and Eocene contemporaries. Within the genus Phenacodus, the more slender P. vortmani, with its more elongate distal elements of the hindlimb, probably was the more efficient runner.

Sedimentary deposits in the Salton Trough of California record the infilling of the northern part of the Gulf of California. The final phase of deposition began about 4.0 Ma with development of the delta plain of the Colorado River and ended about 0.9/0.7 Ma after a period during which deposition was dominated by bedload streams. During the final phase of deposition, a diverse assemblage of mammals characteristic of the Blancan and Irvingtonian Mammal Ages inhabited the area. The Blancan-Irvingtonian boundary is placed in the Fish Creek-Vallecito Creek section at the lowest stratigraphic occurrence of Hammuthus at about 1.77 Ma. The Fish Creek-Vallecito Creek section contains superposed Blancan and Irvingtonian faunas separated by a newly recognized Blancan-Irvingtonian boundary in continuously deposited sediments correlated with the magnetic polarity time scale. It is proposed that the Fish Creek-Vallecito Creek section be recognized as the standard section in which to define the Blancan-Irvingtonian boundary. Taphonomic analysis indicates that skeletal elements accumulated in five major depositional environments: tidal flat, lacustrine, channel, channel "fill", and floodplain. Only the fluvial environments produced significant skeletal abundances and taxonomic diversity. Taphonomic analysis indicates that pre-transport taphonomic processes were more important than fluvial transport in modifying thanatacoenoses. Taphonomic analysis also suggests that taxonomic diversity and relative abundances of large and small mammals are reliably preserved so that assemblages can be used in realistic, but general, analyses of paleoecology and paleocommunity structure. Actualistic and cenogram methods were used to study the Fish Creek-Vallecito Creek paleocommunity. Both methods suggest a savannah-community. The cenogram analysis shows the structure of the paleocommunity based on body size distribution. The data are grouped into assemblages based on the following criteria: change in fluvial environment, change in taxonomic composition, and change in paleoclimate. Stable, discrete small- and large-sized components with homogeneous body-size distributions are separated by an unstable medium-sized component. Results are consistent regardless of how the data are grouped, suggesting confidence in the results, stability in the paleocommunity despite environmental change, and a reality to the existence of the paleocommunity.

The United Verde orebody, a Proterozoic volcanogenic massive sulfide deposit, is hosted by the Cleopatra Formation. The Cleopatra Formation is subdivided into two distinct members, the Upper and Lower, on the basis of alteration facies, whole rock geochemistry and the chemistry of alteration minerals. The Lower member was deposited prior to ore deposition and consists of five major alteration facies. Facies Bl, the most distant from the orebody represents the recharge area for the ore-forming fluid. Facies B2 surrounds the major discharge area or the chlorite pipe. These three facies contain chlorite and quartz as alteration minerals in variable amounts. Two facies, 81 and S2, contain quartz and sericite as alteration minerals. Mass balance calculations show progressive removal of Na and Ca, and addition of MgO and FeO* from the area of recharge (facies Bl) to facies B2 to the chlorite pipe. Whole rock δ¹⁸O values are high relative to least altered Cleopatra Formation in the recharge area and low in the discharge zone. Mineralogy and geochemistry of samples from the Upper member indicate that it was deposited following ore deposition and interacted with fluids rich in silica and iron. The hydrothermal fluid, which is interpreted to have been seawater, evolved to a high temperature slightly acidic, reduced fluid during water-rock interaction(log a₀₂ = -33 to -41; log a(H2S) = -2.6 to -5.0). The fluid δ¹⁸O and δ¹³C₀₂ values increased. Calculated δ¹³C₀₂ and δ¹⁸O fluid values, and sphalerite and chlorite chemistry imply that mixing of the hydrothermal fluid with seawater occurred in the orebody. the upper The levels of the chlorite pipe and in limited range in δ³⁴S values of sulfides is consistent with the derivation of the oreforming fluids from the reduced basal layer of a stratified basin. The study area represents only a small part of the United Verde circulation cell. Increased δ¹⁸O values of the fluid, and the need for a source of Mg, Fe and other metals suggest that the fluids may have circulated into the Shea Basalt.

Paleomagnetic poles were obtained from the Chinle, Kayenta, Summerville, and Morrison Formations. Combined with paleomagnetic poles from the Moenave Formation, poles from the Chinle and Kayenta formations record ∼30 m.y. of North American apparent polar wander (APW) within a regional stratigraphic succession. During the Carnian and Norian stages of the Late Triassic, Chinle poles progress westward. During the Hettangian through Pliensbachian stages of the Early Jurassic, the pattern of APW changed to an eastward progression. Even after correction for 4° clockwise rotation of the Colorado Plateau, a sharp corner in the APW path (J1 cusp) is resolved near the pole from the Hettangian/Sinemurian (∼200 Ma) Moenave Formation (59.4°N; 59.2°E). The J1 cusp implies an abrupt change from counterclockwise rotation of Pangea prior to 200 Ma to clockwise rotation thereafter. Paleomagnetic poles obtained from the Summerville and Morrison formations are consistent with the Middle and Late Jurassic APW path described by the Corral Canyon and Glance Conglomerate paleomagnetic poles as well as a Late Jurassic Cusp (J2 cusp) in the APW path. The APW path described by the J2 cusp, a single Morrison Formation pole, and mid-Cretaceous paleomagnetic poles suggest from ∼150-126 Ma the North American plate experienced a minimum rate of motion of 0.93°/m.y. which is similar to rates calculated for the Late Triassic (0.73°/m.y.) and Jurassic (0.66°/m.y.). This rate is much lower than rates based on previous APW paths. Thermal demagnetization and data analysis indicate that within-site dispersion is an important criterion for selecting sites which retain a high unblocking-temperature, characteristic remanent magnetization (ChRM). This criterion was used to define at least three stratigraphically-distinct, antipodal polarity-zones within each member/formation, suggesting the ChRM was acquired soon after deposition. ChRMs from 15 to 22 sites in the Upper Shale Member of the Chinle Formation define an early Norian paleomagnetic pole position of 57.4°N, 87.8°E (K = 60, A₉₅ = 5.0°). ChRMs from 18 to 43 sites in the Owl Rock Member of the Chinle Formation define a middle Norian paleomagnetic pole position of 56.5°N, 66.4°E (K = 183, A₉₅ = 2.6°). ChRMs from 23 of 35 sites in the Kayenta Formation define a Pliensbachian pole position of 59.0°N, 66.6°E (K = 155, A₉₅ = 2.4°). ChRMs from 15 to 35 sites in the Summerville Formation define a late Callovian pole position of 53.8°N, 133.6°E (K = 25, A₉₅ = 7.5°). ChRMs from 15 sites in the Morrison Formation (9 from the study of Steiner and Helsley [1975]) define a single, ∼147 Ma, paleomagnetic pole position of 64.1°N, 152.4°E (K = 113, A₉₅ = 3.6°).

The use of intramural space is examined in and between structures from the Hohokam site of Snaketown, Arizona. The approach advocated in this volume results from a disenchantment with the efficacy of pre-established functional categories for characterizing structure use and accounting for the variability present. In an effort to transcend the vague concept of house function categories of use-areas are defined which represent widespread regularities in the way intramural space is used and arranged. The latter are identified on the basis of spatial patterns of use that are visible cross-culturally in ethnographies and ethnoarchaeological reports and through the examination of artifact and feature arrangments in the archaeological sample from Snaketown. House types, defined on the basis of differing combinations of use-areas, are examined in the context of spatial aggregates of houses, courtyard groups. Their distributions serve as a basis for deriving inferences regarding the nature, localization, and size of cooperating economic groups at the site. Replication of use-area categories and house types within and between courtyard groups, indicates that cooperating economic groups existed at various levels at Snaketown, both above and below the level of the courtyard group.

Carbon dioxide release from fossil-fuel burning is significant enough that we may soon experience perceptible changes in climate with important human consequences. Man's activities involving deforestation and agriculture have undoubtedly also affected atmospheric CO₂, although quantitative, and even qualitative, net effects of these processes are incompletely understood relative to fossil-fuel production. An accurate reconstruction of past ¹³C/¹²C ratios of atmospheric CO₂ may provide key constraints on the historical activity of the biosphere as CO₂ source or sink. Tree rings appear to be a repository of this information but there is much noise in the collection of previous reconstructions, presumably associated with site selection, radial variability, choice of representative wood chemical constituent, and subtle effects of climate on fractionation. This study attempts to avoid these pitfalls and develop a 50-yr δ¹³C(ATM) record from juniper trees (genus Juniperus), in fact, by taking advantage of the influence of climate on fractionation. Trees were harvested from suitable sites in close proximity to weather stations with monthly records of temperature and precipitation. Ring material was then separated from each of the sections in 5-yr intervals from 1930 to 1979 around their full circumference, and cellulose was extracted from the wood. After measuring δ¹³C of the cellulose by standard mass-spectrometric techniques, a variety of δ¹³C vs. climate functions were examined for each interval. The most useful relationships for at most 7 of the 10 sites were δ¹³C with December temperature or precipitation, because the coefficients were nearly constant from one interval to the next (averaging -0.27%₀ °C⁻¹ for temperature and -0.04%₀ mm⁻¹ for precipitation) and the intercepts differed. Local pollution effects are believed responsible for the three anomalous sites. The separation of these regression lines of different intervals is interpreted as the response of the trees to the changing δ¹³C of atmospheric CO₂ so that δ¹³C(ATM) curves are constructed from this spacing. The shape of the best-fit reconstruction suggests the biosphere has acted as CO₂ source to about 1965 and may now be a net sink. Although these conclusions are limited by certain assumptions and statistical restrictions, evidence from the recent scientific literature tends to support the increasing role of the biosphere as an important carbon sink.

Quantitative tectonic geomorphology is based on a conceptual synthesis between historical and process geomorphology that integrates physical models of geodynamics and erosional kinematics. Geodynamic models of flexure, heat flow and isostasy provide a framework for regional investigation. Topographic analysis and related filtering techniques allow for the description or delineation of regional features. Erosional kinematics modeled by a diffusion equation of heat flow allow the quantitative dating of uplifts across known structures. For large uplifts, the geometry of streams crossing faults is the key element in analyzing age. Theoretically, these faulted stream channels will readjust their gradients with time and these changes can be described as a diffusion process. At this time, however, sufficient data are not available to rigorously constrain estimates of uplift age. For small uplifts, those that result in piedmont fault scarps, statistical analysis of hundreds of scarp profiles suggests that the age of the faulting can be constrained. The apparent morphologic age of fault scarps is strongly affected by variables such as the resistance to erosion of the faulted rock type, but for scarps in alluvium, morphologic dating methods appear to be robust. Quantitative tectonic geomorphology of northwest Arizona and environs suggests that regional topographic patterns can be explained by nonuniform extension of the lithosphere. This process probably began as sub lithospheric erosion about 35 m.y. ago and resulted from a prolonged period of plate convergence and subduction. Superimposed on this predominantly thermal event was younger Basin and Range crustal extension and the opening of the Gulf of California. The Grand Wash fault, the boundary between the Basin and Range and Colorado Plateau physiographic provinces, has been active, though in decreasing amounts, from late Miocene to late Pleistocene time. Morphology of Quaternary piedmont fault scarps that exhibit repeated faulting suggest recurrence intervals on the order of 50,000-100,000 years. The Pitaycachi fault in Sonora, Mexico, which has similar recurrence intervals, broke in 1877, suggesting perhaps that many of the late Pleistocene faults in northwestern Arizona and environs are also due to break.

Santa Eulalia contains two separate, contrasting Pb-Zn-Ag deposits. The East Camp consists of a symmetrically zoned calc-silicate skarn with distal sulfide and tin-bearing orebodies; whereas the west Camp is composed of massive sulfide orebodies with minor proximal calc-silicate skarn and isolated intermediate calcic-iron skarns. Mineralization and alteration are zoned within each camp but do not overlap. Sulfide mineralization in both camps consists of pyrrhotite, sphalerite, galena, and pyrite with lesser amounts of arsenopyrite and chalcopyrite. The East Camp is apparently richer in zinc and copper than the West camp. Mineralization is temporally and spatially related to geochemically identical felsite intrusions which apparently have a common source. Mineralizing fluids followed these felsites through a thick section of evaporites and organic-rich shaly limestones into clean, homogeneous, relatively undeformed, limestone hosts. West Camp mineralization occurs along an interconnected network of vertically discontinuous tight fissures and sill contacts, whereas East Camp mineralization is located along vertically throughgoing faults and dike contacts. strata-bound, but not stratiform, mantos extend off discordant chimneys in both camps. Ore textures reveal that mineralization occurred primarily by limestone replacement. 21 Pressure-corrected primary fluid inclusion homogenization temperatures in fluorite range from 220 to 490 deg. C. Salinities are bimodal with high-salinity (>26.3 equivalent wt% NaCl) and low-salinity (1-12 equivalent wt% NaCl) populations. Mineralogical constraints indicate that the hydrothermal fluids were acid and reduced. Sulfur isotope analyses indicate that the ore fluids varied from -17 to +4 permil without correlation to iron-sulfide species, temperature, or salinity. Co-existing sulfides are commonly in isotopic disequilibrium. Sulfur isotopes from the West Camp are crudely zoned, but no consistent patterns exist in the East Camp. Oxygen and carbon isotope analyses of limestone wallrocks reveal a distinct isotopic alteration halo. A single analysis of gangue calcite from each camp indicates that the ore fluids contained non-carbonate-derived carbon and oxygen, possibly of magmatic origin. Metals were apparently transported as chloride complexes and deposited through coupled dissolution-precipitation replacement reactions. Most ore sulfur apparently came from diagenetic pyrite and sedimentary anhydrite, but some of the sulfur may have had a magmatic source. The metals probably came from the felsite parent magma and this magma may have also contributed fluids. Close similarities between Santa Eulalia and numerous other intrusion-related carbonate-hosted deposits in northern Mexico reinforce these interpretations.

Greenschist-facies, Lower Proterozoic metasedimentary rocks of the Johnny Lyon Rills and Little Dragoon Mountains of southeastern Arizona were deposited prior to the intrusion of an approximately 1690 Ma rhyodacite pluton. Well-preserved primary structures indicate deposition by turbidity currents in an intermediate to neardistal setting. Sandstone compositions suggest derivation from either a complex, heterogeneous source or multiple source terranes that provided mature, quartzose sediment as well as lesser quantities of volcaniclastic detritus. Earliest deformation, predating both intrusion of the rhyodacite and metamorphism, produced sections of melange composed primarily of dismembered turbidite beds, but also incorporating large (up to several km long) blocks of deformed basalt. Subsequent deformation, in part post-dating intrusion of the rhyodacite and in part coinciding with metamorphism, affected both melange and coherent strata, and involved isoclinal folding and layerparallel faulting and shearing. It is proposed that turbidite deposition occurred in a trench associated with a north-dipping subduction zone or on ocean floor outboard of such a trench. Melange formed primarily by ductile disruption of unlithified sediments within the subduction zone. Basalt blocks incorporated within the melange represent fragments of oceanic crust or seamounts detached from the lower plate during subduction. Later deformation and intrusion of the rhyodacite occurred within an accretionary prism above the subduction zone. Deformation within the prism ended prior to intrusion of the 1625 ± 10 Ma posttectonic Johnny Lyon Granodiorite.