Brian T. Huber | Geology Reports

USGS2024

Microfossil biostratigraphy and paleoenvironments of Cretaceous and Pliocene sediments along Greens Mill Run, North Carolina, USA

Cretaceous sediments are disconformably overlain by Pliocene sediments along the banks of Greens Mill Run, Greenville, North Carolina, located in the central coastal plain. The Cretaceous sediments, composed of glauconitic sand and clay, have previously been informally considered part of the Maastrichtian Peedee Formation. The Pliocene sediments are assigned to the Yorktown Formation and consist of shelly, muddy sand overlain with a gradational contact by shell-poor, muddy sand. Foraminifera are abundant in the Cretaceous unit and are dominated by the planktic foraminifera Guembelitria cretacea. Low planktic foraminiferal diversity, the absence of single and double-keeled species, the dominance of planktic over benthic foraminifera, and the occurrence of glauconite and phosphorite grains indicates a middle neritic environment. The age of the Cretaceous unit is late Campanian (Zone CC22c), as indicated by the co-occurrence of the calcareous nannofossils Reinhardtites levis and Reinhardtites anthophorus. For this reason, we assign these deposits to the Donoho Creek Formation of the Black Creek Group rather than to the lithologically similar and younger Peedee Formation. Benthic foraminifera dominate the lower part of the Yorktown Formation, are similar to those from the Rushmere Member of the Yorktown Formation in the southern Salisbury Embayment, and indicate deposition in an inner to middle neritic environment. Phosphorite peloids and intraclasts are likely reworked from underlying strata and suggest wave ravinement and deposition during transgression, which is further supported by a fining upward trend. The upper part of the Yorktown Formation exposure, characterized by abundant molds of small bivalves and barren of foraminifera, represents the Morgarts Beach Member. Sedimentological data are consistent with foraminiferal data as far as expected depositional energy. A restricted inner neritic or estuarine environment is indicated.

North Carolina↗

USGS2022

Calcareous plankton biostratigraphic fidelity and species richness during the last 10 m.y. of the Cretaceous at Blake Plateau, subtropical North Atlantic

Species distributions of well-preserved and diverse assemblages of planktonic foraminifera and calcareous nannofossils spanning the last 10 m.y. of the Cretaceous (middle Campanian through Maastrichtian) are analyzed from samples taken across a 1400 m depth transect at Blake Nose in the western subtropical North Atlantic (Ocean Drilling Program Sites 1049, 1050 and 1052). Age models constructed by integrating foraminiferal, calcareous nannofossil, and magnetic polarity datum events provide a reliable framework for temporal correlation of the sites. This framework enables comparisons of species richness and abundance among sites and evaluation of the reliability of first and last appearance datums for regional and global correlation. Among the standard primary zonal marker datums, six of nine planktonic foraminifer and six of seven calcareous nannofossil events are considered reliable for constraining the age-depth models. Secondary datum ages calculated for 17 planktonic foraminiferal events suggest correlation offsets among the three sites of <0.1 m.y. for four species (including Pseudoguembelina praehariaensis Tur and Huber n. sp.), 0.1–0.5 m.y. for six events, and 0.6–1.0 m.y. for eight species. Secondary calcareous nannofossil datum ages calculated for six species show less reliability, with offsets of <0.1 m.y. for one species, 0.7 m.y. for one species, and 1.0–1.5 m.y. for the remaining four species. The distinctly identifiable new species Trinitella suturis Tur and Huber has lowest occurrences that are diachronous by as much as 1.73 m.y. among the Blake Nose sites. Occurrence rarity is the most likely explanation for the age offsets of this and other diachronous species. Planktonic foraminiferal assemblages show no significant differences in species composition and relative abundance among the three sites, suggesting the sites were all located below a single oligotrophic surface water mass. Species richness counts pooled in 200 kyr bins for the Blake Nose sites reveals high species origination rates from the late Campanian through early Maastrichtian and highest species richness (51–63 species) during the Maastrichtian. The only significant extinction pulse during the mid-Campanian through Maastrichtian occurs between 66.2 and 66.4 Ma with loss of five species representing ∼9% of the assemblage. These extinctions occur at the same time as a globally recognized warming event correlated with a pulse of eruptions at the Deccan Traps in India. Calcareous nannofossil assemblages show no significant change in relative abundance among the three sites. Two significant extinction events are documented: one from 75.20 to 75.40 Ma with a loss of six species representing ∼6% of the assemblage and one from 66.2 to 66.4 Ma with a loss of nine species representing ∼9% of the assemblage. The former event is associated with a hiatus at the base of Zone CC24, and the latter corresponds to Deccan Trap warming. Hiatuses are identified at all three Blake Nose sites near the base of the Maastrichtian (∼71.5 Ma; lowermost Pseudoguembelina palpebra /CC24 Zone) and only at the deeper Sites 1049 and 1050 in the mid-Maastrichtian (∼67.2 Ma; Pseudoguembelina hariaensis /CC26b Zone) and the mid-Campanian (∼75.9 Ma; base of Radotruncana calcarata /CC22 Zone). Slumping from across the shelf and slope could have caused the early Maastrichtian hiatus while changes in the pattern and strength of deep-water circulation may have been responsible for the mid-Maastrichtian and mid-Campanian hiatuses.

Cretaceous Research↗

USGS1997

The Blake Nose Cretaceous-Paleogene (Florida Atlantic margin, ODP Leg 171 B): An exemplar record of the Maastrichtian-Danian transition

During ODP Leg 171B, devoted to the analysis of the Blake Plateau margin in front of Florida, 16 holes have been drilled in 5 distinct sites. The sites have documented a sedimentary succession ranging in age from Aptian to Eocene. Emphasis has been put on critical periods, comprising the Paleocene-Eocene transition, the Cretaceous-Tertiary boundary which has been cored in excellent conditions, the middle Maastrichtian extinctions and the Albian anoxic episodes.

Comptes Rendus de l'Academie des Sciences - Serie ↗