Environments of Deposition of the Moenkopi Formation in North-Central Arizona
Figure 4: Isopach Map of Moenkopi ...
Figure 26: Correlation of Moenkopi ...
Figure 35: Columnar Sections of ...
Figure 43: Fence Diagram of the ...
AuthorBaldwin, Evelyn Joan
Geology, Stratigraphic -- Triassic
Geology -- Arizona -- Coconino County
Geology -- Arizona -- Navajo County
Geology -- Arizona -- Moenkopi Formation
Moenkopi Formation (Ariz.)
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the Antevs Library, Department of Geosciences, and the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author or the department.
AbstractIn north-central Arizona, the Moenkopi Formation of Triassic age consists of generally unfossiliferous red mudstones, siltstones, gypsum, and sandstones that contain abundant sedimentary structures, such as ripple marks, cross-stratification, ripple laminae, salt crystal casts, mud cracks, sole marks, parting lineation, and core-and-shell structures. Three informal members were established for this study: the lower member, the lower massive sandstone, and the upper member. Flaser, wavy, and lenticular bedding, bimodal distribution of ripple laminae dips, parallel ripple marks dominant over cuspate ripple marks, gypsum beds and veins, salt crystal casts, and lack of channel deposits are the suite of sedimentary features that are interpreted to indicate a tidal-flat environment during deposition of the lower member. The very fine grained lower massive sandstone can be divided into four subunits, which were formed by a transgression-regression of the sea. Wavy and ripple laminated beds in subunit one were probably deposited in very shallow water. Medium-scale wedge-planar and trough sets of cross strata with mean dip directions to the southeast make up subunit 2 and indicate megaripples formed by longshore drift. Subunit 3 consists of lenticular, wavy, pod-shaped beds that were created in water shallower than that for subunit 2. Continuous, large-scale, low-angle cross strata of uniform thickness and medium-scale wedge-planar and trough sets of cross strata characterize subunit 4 and are typical of beach deposits. The significant sedimentary features in the upper member are unimodal distribution of ripple laminae dips, cuspate ripple marks dominant over parallel ripple marks, channel deposits with shallow trough cross strata, an increase in the number and thickness of sandstone and siltstone beds compared with the lower member, plus vertebrate bones, tracks, and plant impressions. This suite of features indicates a flood-plain environment. Early in Moenkopi time, north-central Arizona was a tidal flat and sabkha. The sea to the west fluctuated east and west and finally transgressed over the entire area. As the sea regressed, a beach formed, and rivers flowing from the east deposited sediment on a westward-prograding flood plain. In the northern, southern, and central portions of the region, sabkhas existed for a time during regression. At the end of Moenkopi time, the entire area was a flood plain. Considering the association of red beds and evaporites, the absence of fossils in the lower member and the lower massive sandstone, the paleowind directions, and the theory of continental drift, the climate during early and middle Moenkopi time was probably hot and arid. The influx of sandstones, the presence of Calamites (?) impressions, and trackways and bones of amphibians in the upper member suggest that the climate became more humid at the end of Moenkopi time.
Degree ProgramGraduate College
Degree GrantorUniversity of Arizona
Showing items related by title, author, creator and subject.
Water infiltration and percolation at the University of Arizona radioactive waste burial site, Pinal County, ArizonaSalvetti, Joseph Peter.; Dutt, Gordon R. (The University of Arizona., 1984)The University of Arizona produces different types of radioactively contaminated waste. It is shipped to a burial site located on the Oracle Agricultural Center in Pinal County, Arizona and disposed of in shallow pits. This study dealt with water movement at the disposal site. Monitoring of water movement through young pits was accomplished with a neutron probe. It was found that due to slumping and cracking of the pit cap, the younger pits were very susceptible to greater than normal water infiltration. Further data were gathered around the older pits by deep soil sampling for tritium activity. Water fluxes and travel times to the major aquifer were calculated from these data. Estimates of travel times range from 40 to 230,000 years to reach the principal aquifer at 150 m.
A recursive programming analysis of water conservation in Arizona agriculture : a study of the Phoenix active management areaLierman, Wally Kent.; Wade, James C.; Ayer, Harry W.; Cory, Dennis (The University of Arizona., 1983)Arizona agriculture faces many changes in the near future. One of the most imminent changes will come from the enactment of the 1980 Arizona Groundwater Management Act. The 1980 AGWMA is designed ultimately to curtail the use of groundwater in Arizona. Agriculture will be affected since this sector used approximately 87 percent of all water in the State in 1980. This study reports on the possible effects that a proposed pump tax and water duty policy would have on agriculture within the Phoenix Active Management Area. The PAMA is one of four such areas in the State that have been identified as needing groundwater use management. The results of this study indicate that the proposed water duty is more effective in curbing groundwater use than the proposed pump tax. Investment in more water application efficient irrigation technologies is also important in this study. However, substantial amounts of capital investment funds will be needed to begin this investment.
The ethnobotany and phenology of plants in and adjacent to two riparian habitats in southeastern Arizona.Asdall, Willard Van; Adams, Karen Rogers.; Mason, Charles T.; Martin, Paul S.; Davis, Owen K.; Turner, Raymond M. (The University of Arizona., 1988)Two riparian habitats in southeastern Arizona provide the setting for a study of 127 plants useful to human foragers. A view of plant part availability is based on annual phenological profiles, and on historic and prehistoric records of plant use. Food choice is limited in March and April, but high August through November. Riparian plants also offer numerous non-food resources. Trees and shrubs serve more needs in relation to number of available species than do perennial herbs (including grasses) and annuals. Southwestern ethnographic literature hints that certain native taxa (Panicum, Physalis, Populus, Salix, Typha and Vitis) might receive special care. Inherent qualities of parts, coupled with ethnographic records of preparation and use, provide a basis for speculation on which parts might survive in an ancient record. Most are expected to disintegrate in open sites. Parts sought for different needs can enter a dwelling via diverse routes that produce confusingly similar archaeological debris. Modern experiments to wash pollen from 14 separate harvests permit evaluation of plant fruit and leaves as pollen traps, to help interpret pollen recovered from ancient dwellings. High amounts of Berberis, Rumex and Ribes pollen, sometimes in clumps or as tetrads, travel on harvested fruit. Arctostaphylos, Monarda, Oxalis, Rhus, Rhamnus, Vitis and Juniperus parts carry lower amounts. Quercus and Gramineae pollen grains travel on parts of other taxa, as well as on their own fruit. The phenological profiles offer insight into group life-form activities in response to local temperature and precipitation trends. Rising and maximum temperatures coincide with intense vegetative and reproductive activity for trees, shrubs, herbaceous perennials, and annuals. Increased levels of precipitation coincide with maximum flowering and fruiting of herbaceous perennials and fall annuals. Limited data on six taxa from Utah generally agrees with observations in this study, suggesting strong genetic control in the phenology of some riparian taxa.