Observational foundation for sequence modeling

The design of useful models for predicting sequences and facies patterns of sedimentary cycles depends on an observational foundation that includes the recognition and adequate understanding of fundamental depositional sequences. Six facets must be met. The modeler must have (1) adequate documentation of sequence character; (2) adequate characterization of spatial and directional variability and continuity of facies; (3) an adequate database on the influence of primary and secondary controls on sedimentation; (4) an understanding of interaction of controls on sedimentation; (5) an understanding of limits of physical, biologic, and chemical influences; and (6) an understanding of diagenetic modifications to sequence nature and thickness. In addition, the models should work from the fundamental depositional sequence. The modeler should use caution in applying models designed for one scale of sedimentary sequence to another scale. Examples illustrate the necessity for meeting each facet

Observational foundation for sequence modeling

The design of useful models for predicting sequences and facies patterns of sedimentary cycles depends on an observational foundation that includes the recognition and adequate understanding of fundamental depositional sequences. Six facets must be met. The modeler must have (1) adequate documentation of sequence character; (2) adequate characterization of spatial and directional variability and continuity of facies; (3) an adequate database on the influence of primary and secondary controls on sedimentation; (4) an understanding of interaction of controls on sedimentation; (5) an understanding of limits of physical, biologic, and chemical influences; and (6) an understanding of diagenetic modifications to sequence nature and thickness. In addition, the models should work from the fundamental depositional sequence. The modeler should use caution in applying models designed for one scale of sedimentary sequence to another scale. Examples illustrate the necessity for meeting each facet

Classification of the Pennsylvanian rocks of Illinois as of 1956

Ope

Pennsylvanian faunas of the Beardstown, Glasford, Havana, and Vermont Quadrangles.

Bibliography: p. 59

Geology and mineral resources of the Alexis Quadrangle.

At head of title: State of Illinois. Department of Registration and Education. Division of the State Geological Survey.Four folded plates (maps, and 2 diagrams) in pocket.Includes bibliographical references

Oil possibilities of the Alexis quadrangle, Mercer and Warren Counties, Illinois

Caption title

Fining-upwards sedimentary sequences generated in seagrass beds

Shallow-marine clastic and carbonate environments of southeast Florida contain fining-upwards sedimentary sequences being generated by beds of the seagrass, Thalassia testudinum . Lateral seaward migration of flute-shaped sand pockets (storm blowouts) in the grass platform produces a lenticular fining-upwards package 10-50 m in width, 20-100 m in length, and 0.3-2 m in thickness. Migration and vegetative restabilization of recurring "blowouts" on a grass platform can produce a composite sequence containing numerous complete or stacked incomplete fining-upwards packages. A complete fining-upwards sequence consists of 1) an erosional base, 2) a coarse basal shell layer representing the winnowed lag of the eroded, preexisting grass-stabilized platform, 3) a ripple-laminated, well-sorted, medium-grained sand zone representing the mobile sand on the leeward slope of the blowout, and 4) a shelly, bioturbated sand or silty sand having a strongly bimodal texture (modes at 100 and 500 µm) in which the fine mode dominates upwards. This upper portion records increased trapping of storm suspensions and decreased bedload transport as seagrasses are reestablished. The mollusks Chione cancellata and Codakia orbicularis characterize the grass-stabilized zone. The distinctive textural sequence and molluscan assemblage serve to differentiate these biogenically induced fining-upwards sequences from others in the geological record

A history of poor economic and environmental renourishment decisions in Broward County, Florida

Southeast Florida's beaches, which are heavily developed and imperiled by rising sea level, continue to be seriously mismanaged and uneconomically maintained and to generate increasing environmental stress for adjacent marine habitats. Broward County heads the list of counties that stretch from St. Lucie southward to Miami-Dade. Five serious problems plague the stability of these barrier-island shorelines: inlet disruption of littoral drift; beach management that enhances shore erosion (lack of shore vegetation, inappropriate vehicular traffic, and structural protections that enhance erosion); historically very poor-quality renourishment sediment (in size and durability); strong resistance by coastal engineering and dredging firms and counties to embrace an understanding of sandy shore dynamics; and a philosophy that renourishment projects are a solve-all management approach to maintaining beaches and protecting infrastructure. This has led to seriously destabilized beaches, overly aggressive beachfront development, major economic waste, and severe environmental degradation to adjacent marine waters and associated valuable sandy bottom and hard-bottom communities. Many of these sandy shorelines may well not survive this global warming century of rapidly rising sea level. It is economically and environmentally critical for both the future risks to be understood and for lessons from the repeated failed history of beach management to be learned. Continued mismanagement will shorten the inhabitable lifetime of this developed sandy coast by decades and at great economic and environmental cost

Geology and mineral resources of the Beardstown, Glasford, Havana, and Vermont Quadrangles

Includes bibliographical references and index