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Laurel M. Bybell

Publications and source records attributed to Laurel M. Bybell.

52 records · Page 3Linked to original sources
USGS1984

Age of the Comfort Member of the Castle Hayne Formation, North Carolina

The biostratigraphic and chronostratigraphic position of the Comfort Member of the Castle Hayne Formation has been the subject of much debate. At the Martin-Marietta Quarry at Castle Hayne, New Hanover County, North Carolina, the planktic foraminifers indicate an assignment within an interval of the uppermost Turborotalia frontosa Zone to the Turborotalia pomeroli Zone. The calcareous nannofossils indicate an assignment to the middle part of the Chiasmolithus solitus Zone. The dinocyst data indicate placement in the upper part of the Kisselovia coleothrypta Zone of Costa and Downie. These zonal units are considered to be within the middle Eocene of international usage, and, on the basis of the time scale used in this paper, the Chiasmolithus solitus Zone represents a time interval of 42.1 to 45.4 megaannums (Ma). This differs significantly from a Rb/Sr glauconite date of 34.8 ± 1.0 Ma previously obtained at the same locality.

North Carolina↗
USGS1984

Significant unconformities and the hiatuses represented by them in the Paleogene of the Atlantic and Gulf Coastal Province

A biostratigraphic, chronostratigraphic, and magnetostratigraphic model has been calibrated to produce a new time scale for the Paleogene. The model gives the biostratigraphic position and duration represented by significant unconformities in three areas of the Atlantic and Gulf Coastal Province: 1) western and central Alabama; 2) South Carolina; and 3) central Virginia to southwestern Maryland. In these areas, the most significant unconformity, in terms of duration represented and lateral extent, is found in the lower Eocene. In Alabama, this unconformity centers around 51.4 m.y. and represents a hiatus of about 1.4 m.y. In South Carolina, this unconformity centers around 50.3 m.y. and represents a hiatus of about 10.0 m.y. In Virginia-Maryland, the lower Eocene unconformity centers around 49.0 m.y. and represents a hiatus of about 7.3 m.y. A significant unconformity exists between the Cretaceous and Tertiary in all three areas. On the Atlantic coast the Cretaceous-Tertiary unconformity represents some missing Danian and significant missing Maestrichtian. In Alabama, however, there is virtually a complete Danian section and it is only most of the upper Maestrichtian that is missing. There are significant regional unconformities in all three areas.

Book chapter↗
USGS1983

Reworked Hantkenina speciments at Little Stave Creek, Alabama

The Eocene-Oligocene boundary in Mississippi and Alabama has been traditionally placed between the Shubuta Member of the Yazoo Formation and the overlying Red Bluff Formation (or its carbonate facies equivalent, the Bumpnose Formation). Consequently, the presence of Eocene planktonic foraminifers in the Red Bluff and Bumpnose has long been attributed to reworking. To test the validity of this hypothesis, samples were collected on both sides of the boundary from the upper "Shubuta" and Bumpnose units at Little Stave Creek, Alabama, and were examined for both calcareous nannofossil and planktonic foraminiferal content. The calcereous nannofossil assemblage, preserved in the matrix from inside handpicked specimens of Hantkenina from both units, was demonstrably older than the calcareous nannofossil assemblage from the surrounding sediment. Thus, at least some of the Hantkenina specimens in both the "Shubuta" and Bumpnose are indeed reworked, which not only confirms the original hypothesis regarding reworking within the Red Bluff and Bumpnose, but also indicates that the last occurrence of Hantkenina , the "Shubuta"-Bumpnose contact, and the Eocene-Oligocene boundary in the U.S. Gulf Coast may not be equivalent.

Alabama↗
USGS1982

Biostratigraphy and paleoecology of lower Paleozoic, upper Cretaceous, and lower Tertiary rocks in U.S. Geological Survey New Madrid test wells, Southeastern Missouri

The paleontology and biostratigraphy of Tertiary, Cretaceous, and Paleozoic rocks in the upper Mississippi embayment are incompletely known because marine fossils are only locally present in these rocks. This study concerns material from two U.S. Geological Survey test wells drilled in New Madrid County, southeastern Missouri, as part of earthquake hazard studies in the northern Mississippi Embayment. Test well1 sampled lower Tertiary strata to a depth of 146ft; these strata were found to be late Eocene in age on the basis of sporomorphs. Test well1-X, 29ft northwest of well1, provided cuttings and cores from lower Tertiary, Upper Cretaceous, and lower Paleozoic rocks to a total depth of 2,316 ft below the Kelly bushing (at an altitude of 288 ft). Lithologic evidence suggests that the base of the Jackson Formation may be at 270 ft, but sporomorphs indicate that the base of the Jacksonian Stage (upper Eocene) is possibly at a depth of about 350ft in test well1-X. Lithologic units of the Claibornian Stage (middle Eocene) here consist of the Cockfield(?) and Cook Mountain(?) Formations and Memphis Sand, in descending order. The Claibornian could not be subdivided using sporomorphs from cuttings, but sporomorphs show that the top of the Sabinian Stage (top of the lower Eocene) is at about 1,055 ft; lithologically, the top of the Wilcox Group (top of the Flour Island Formation) is at 1,048 ft. Sporomorphs suggest that the top of the lower Sabinian (top of the Paleocene) is within the Flour Island Formation at about 1,105 ft. The next major lithologic break, the top of the Fort Pillow Sand at 1,186 ft, does not coincide with any detectable biostratigraphic boundary. Lithologically, the interval from 1,339 to 1,377 ft may belong to the Old Breastworks Formation; dinoflagellates from cuttings indicate that this interval is likely to be late Midwayan in age and, therefore, correlative with the Naheola Formation of the eastern Gulf Coast. The Porters Creek Clay extends from a probable top at 1,377 ft to 1,691 ft, and the base of the underlying Clayton Formation (Tertiary-Cretaceous contact) is at 1, 703 ft. Calcareous nannofossils, dinoflagellates, foraminifers, mollusks, ostracodes, and sporomorphs from continuous cores of the Porters Creek Clay and Clayton Formation indicate that the upper half of the Porters Creek correlates with the upper part of the same formation or perhaps partly with slightly younger rocks in the eastern Gulf Coast, the lowermost Porters Creek appears to correlate with the upper part of the Clayton Formation of the eastern Gulf Coast and with the Kincaid Formation of Texas, and the thin Clayton of the test well probably correlates with only the lower part of the thicker Clayton of the eastern Gulf Coast. Sporomorphs from McNairy Sand (Upper Cretaceous) cores indicate Maestrichtian and perhaps latest Campanian Age. Lower Paleozoic dolostone from 2,023 ft to total depth at 2,316 ft is barren of identifiable fossils except for a probable fragment of the fish Anatolepis; the dolostone is probably Late Cambrian in age. The McNairy Sand of New Madrid well 1-X seems to have been deposited in nonmarine to nearshore marine environments; the Clayton Formation and lower part of the Porters Creek Clay were deposited under marine conditions during an early Paleocene marine transgression. A major regression followed that continued through the end of Porters Creek time and perhaps into Naheola (late Midwayan) time; the Sabinian, Claibornian, and Jacksonian strata in southeastern Missouri were deposited primarily or entirely in nonmarine environments.

Missouri↗