Lithostratigraphic analysis of cyclical phosphorite sedimentation within the Miocene Pungo River Formation, North Carolina continental shelf / by Patrick M. Mallette.
| Author/creator | Mallette, Patrick M. author. |
| Other author | Riggs, Stanley R., degree supervisor. |
| Other author | East Carolina University. Department of Geology. |
| Format | Theses and dissertations |
| Production | 1986. |
| Description | 155 leaves, 10 unnumbered leaves of plates : illustrations, maps ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | The Miocene Pungo River Formation occurs in outcrop and shallow 2 subcrop across 5000 km of the North Carolina continental shelf in Onslow Bay. The formation contains three N-S trending, unconformity bound, depositional sequences which dip gently seaward. These sequences, referred to as the Frying Pan Sequence (late Burdigalian), Onslow Bay Sequence (Langhian) and Bogue Banks Sequence (Serravallian) are products of third-order sea-level cycles and were originally recognized on the basis of seismic and biostratigraphic techniques. Lithologic descriptions from 95 nine-meter vibracores demonstrate that the depositional sequences can also be distinquished on the basis of their characteristic lithofacies, which reflect deposition in shelf, shelf margin and shelf environments, respectively. The Frying Pan Sequence comprises four major lithofacies: 1) phosphorite (10-65% phosphate), 2) siliciclastic (sand and mud), 3) mixed carbonate and siliciclastic, and 4) foraminiferal quartz sand. The Onslow Bay Sequence comprises three major lithofacies: 1) biogenic carbonate, 2) interbedded quartz sand and dolosilty mud and 3) organic rich mud. The Bogue Banks Sequence is subdivided into five major lithofacies: 1) quartz sand, 2) phosphatic quartz sand (3-9% phosphate), 3) phosphorite quartz sand (10-25% phosphate), 4) dolosilty mud, and 5) carbonate. Lithofacies distribution within the Frying Pan and Onslow Bay Sequences is controlled by antecedent topography and location of sediment source areas. In northern Onslow Bay, biogenic carbonate sediments are associated with the Cape Lookout High, a shallow region with low siliciclastic influx. Siliciclastic sediments of central Onslow Bay fine southward away from a source area on the adjacent landmass. Minimum dilution by siliciclastic sediments in southern Onslow Bay, coupled with upwelling and reducing bottom conditions, resulted in accumulation of organic matter and authigenesis of phosphorite and dolomite. Lithofacies distribution within the Boque Banks Sequence could not be directly related to prominent paleotopographic features or sediment source areas. Cyclical patterns of sedimentation within third-order depositional sequences represent the lithologic response to high-frequency glacio eustatic sea-level fluctuations. The ideal lithic cycle consists of basal muddy siliciclastic sands, overlain by muddy foraminiferal phosphorite sands, overlain by foraminiferal or diatomaceous muds. This vertical succession of lithologies represents deposition during the transgressive phase of a fourth-order sea-level cycle. Ideal lithic cycles are not laterally persistent but grade into either uniform or interbedded sediment sequences. Diagenesis during subaerial and submarine exposure results in dissolution of primary sedimentological components including phosphate, dolomite, calcareous macrofossils, and calcareous and siliceous microfossils, as well as reprecipitation and neogenesis of secondary sedimentological components including phosphate, dolomite, zeolite and calcite cements. |
| General note | "Presented to the faculty of the Department of Geology ... in partial fulfillment of the requirements for the degree Master of Science in Geology." |
| General note | Advisor: Stanley R. Riggs |
| Dissertation note | M.S. East Carolina University 1986 |
| Bibliography note | Includes bibliographical references (leaves 133-139). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
Availability
| Library | Location | Call Number | Status | Item Actions |
|---|---|---|---|---|
| Joyner | University Archives | ASK AT SPECIAL COLLECTIONS DESK | ✔ Available | Request Material |
| Joyner | NC Microforms | MICROFILM* | ✔ Available | |
| Electronic Resources | Access Content Online | ✔ Available |