USGS Science⌕ Search

Geology topics

Jean Self-Trail

Publications and source records attributed to Jean Self-Trail.

At least 37 records · Page 2Linked to original sources
USGS2020

Depositional sequence stratigraphy of Turonian to Santonian sediments, Cape Fear arch, North Carolina Coastal Plain, USA

A new sequence stratigraphic framework for Turonian to Santonian (94-84 Ma) sediments is established using data from the USGS Kure Beach and Elizabethtown cores collected from the Atlantic Coastal Plain of North Carolina (NC). These sediments represent some of the oldest marine units deposited on the southeastern Atlantic Coastal Plain and record the early development of a clastic wedge atop crystalline basement. Sediments were deposited as transitional marginal-marine to marine units in a complex interplay of fluvial, estuarine, and shelf environments. Repetitive lithologies and minimal biostratigraphic control requires an integrated analysis of grain-size data, geophysical logs, biostratigraphy, and 87Sr/86Sr isotopic data to identify systems tracts and establish a sequence stratigraphic framework. From this integrated approach, three Turonian to Santonian sequences in the Elizabethtown core and six in the Kure Beach core are identified. The new sequences from oldest to youngest are Clubhouse II, Fort Fisher I, Fort Fisher II, Collins Creek I, Collins Creek II, Pleasant Creek I, and Pleasant Creek II. Sequences from North Carolina document significant shifts of global and regional sea-level during greenhouse conditions in the early Late Cretaceous. Maximum sea-level rise occurred globally during the early Turonian and is documented from the marine sediments of the Clubhouse II sequence. This sequence is unconformably overlain by terrestrial sediments deposited during a major fall in sea level and maximum progradation of the shoreline, as evidenced by the Fort Fisher I sequence. Global sea-level rise in the Coniacian resulted in the deposition of the Fort Fisher II sequence, which is present only in the Kure Beach core. Local marine circulation and erosion on the shelf is suggested by the absence of the Collins Creek I sequence at Kure Beach; this sequence is present only in the up-dip Elizabethtown core. Activation of a possible buried fault structure along the Cape Fear arch resulted in the formation of a regional depocenter during the late Coniacian to early Santonian and is reflected in the unusual thickness of the Collins Creek II and Pleasant Creek I sequences. The return to a more global sea-level influence occurred in the late Santonian with the deposition of the Pleasant Creek II sequence. A comparison of temporal distribution of sequences in the Elizabethtown and Kure Beach cores to corresponding sequences in New Jersey indicates significant differences in erosional and tectonic processes in the Cape Fear region during the Turonian and Santonian.

North Carolina↗
USGS2020

Cross section of the North Carolina coastal plain from Enfield through Cape Hatteras

Introduction The Atlantic Coastal Plain, the southeasternmost physiographic province in the United States, is underlain by strata that regionally dip gently eastward and gradually thicken toward the Atlantic Ocean basin. These strata, ranging in age from Middle Jurassic to Holocene, accumulated along the eastern margin of North America after the break-up of the supercontinent Pangaea during the Early Jurassic. In the east-central United States north of Florida, Cape Hatteras is the point of land that most closely approaches the eastern edge of the Atlantic Continental Shelf of the United States. In 1946, Esso (now part of ExxonMobil) drilled a deep oil exploration well to basement rock near the Cape Hatteras lighthouse. No oil or gas was found there, or in any of the other test wells that were drilled within the onshore North Carolina Coastal Plain. Recent work indicates that the top of the oil window lies at 9,000 feet near the base of the Cape Hatteras Esso #1 test well. Therefore, any mature petroleum source rocks that may be present in the North Carolina Coastal Plain are only likely to be found east of the present coastline. Although the Cape Hatteras test well did not produce oil or gas, it did produce a wealth of stratigraphic information about the outer portion of the onshore Atlantic Continental Shelf. Advances in global stratigraphic correlation, in tandem with our analyses of calcareous nannofossils and dinoflagellate cysts (dinocysts) from the Cape Hatteras test-well spot samples have produced significant advances beyond earlier interpretations of this well and other deep test wells inshore of Cape Hatteras. These results, when coupled with work done offshore of Cape Hatteras, have allowed us to create a more detailed cross section of the North Carolina Coastal Plain and adjacent continental shelf than previously possible.

North Carolina↗
USGS2019

Geology and biostratigraphy of the Upper Floridan aquifer in the greater Savannah region, Georgia and South Carolina

The Upper Floridan aquifer (UFA) of South Carolina, Georgia, Alabama, Mississippi, and Florida has been considered a regionally continuous stratigraphic sequence of Eocene to Miocene carbonate strata, with documented unconformities based on lithology and biostratigraphy. As part of an investigation of the regional subsurface geologic framework in the Atlantic Coastal Plain Province, three deep cores were drilled by the U.S. Geological Survey at Pineora, Effingham County, Georgia; Cockspur Island, Chatham County, Georgia; and Palm Dunes, Beaufort County, South Carolina. The age of the UFAbased on calcareous nannofossil biostratigraphy ranges from early Oligocene to early Miocene in Pineora, late Eocene to late Oligocene in Cockspur Island, and late Eocene to questionably Miocene in Palm Dunes. Thin section analyses identified eleven unique microfacies across the study area and suggests that the sediments were most likely transported by oceanic currents at the time of deposition. Disconformities are identified from the Pineora and Palm Dunes cores and channel incision is documented at the top of the UFA in the Palm Dunes core. This study 1) documents how existing formation and time stratigraphic boundaries cross hydrogeologic units, 2) shows the complex geologic nature of the Upper Floridan aquifer across a relatively limited area, 3) sets forth a better understanding of how lateral and vertical changes in the lithologic units of the UFA affect permeability and porosity, and thus subsurface hydrologic flow, across the region, and 4) highlights the problems faced by legislators when implementing groundwater use regulations intended to slow salt water intrusion and drawdown.

Georgia, South Carolina↗
USGS2018

Evidence for shelf acidification during the onset of the Paleocene-Eocene Thermal Maximum

A transect of paleoshelf cores from Maryland and New Jersey contains a ~0.19 m to 1.61 m thick interval with reduced percentages of carbonate during the onset of the Paleocene-Eocene Thermal Maximum (PETM). Outer paleoshelf cores are barren of nannofossils and correspond to two minor disconformities. Middle paleoshelf cores contain a mixture of samples devoid of nannofossils and those with rare specimens characterized by significant dissolution (i.e., etching). The magnitude of the decrease in carbonate cannot be explained by dilution by clastic material or dissolution resulting from the oxidation of organic matter during early diagenesis. The observed preservation pattern implies a shoaling of the calcite compensation depth (CCD) and lysocline to the middle shelf. This reduced carbonate interval is observed during the onset of the PETM on other continental margins raising the possibility that extreme shoaling of the CCD and lysocline was a global signal which is more significant than in previous estimates for the PETM. An alternative scenario is that shoaling was restricted to the northwest Atlantic, enhanced by regional and local factors (eutrophication from rivers, microbial activity associated with warming) that exacerbated the impact of acidification on the shelf.

Maryland, New Jersey↗
USGS2018

Ecological changes in the nannoplankton community across a shelf transect during the onset of the Paleocene-Eocene Thermal Maximum

Warming and other environmental changes during the Paleocene‐Eocene thermal maximum (PETM) led to profound shifts in the composition and structure of nannoplankton assemblages. Here we analyze the nature of these changes in expanded records from the Cambridge‐Dorchester and Mattawoman Creek‐Billingsley Road cores in Maryland. These cores comprise part of a transect of five paleoshelf cores from Maryland and New Jersey. We integrate multivariate analysis of assemblage data with proxy data to revise understanding of the paleoecological affinities of key species. In particular, Discoaster and Fasciculithus are interpreted as thermophiles without adaptation to particular nutrient levels, while Hornibrookina is considered an opportunist adapted to highly variable nearshore environments. Together the cores show consistent margin‐wide changes across the onset of the PETM, including a pulse of preevent warming, possibly combined with lower salinity, high seasonality, or increased turbidity. The event itself was characterized by continued warming and eutrophication across the paleoshelf. The Maryland sites experienced higher environmental variability as a result of their proximity to large river systems.

Paleoceanography and Paleoclimatology↗
USGS2018

Paleocene–Eocene Thermal Maximum prolonged by fossil carbon oxidation

A hallmark of the rapid and massive release of carbon during the Palaeocene–Eocene Thermal Maximum is the global negative carbon isotope excursion. The delayed recovery of the carbon isotope excursion, however, indicates that CO 2 inputs continued well after the initial rapid onset, although there is no consensus about the source of this secondary carbon. Here we suggest this secondary input might have derived partly from the oxidation of remobilized sedimentary fossil carbon. We measured the biomarker indicators of thermal maturation in shelf records from the US Mid-Atlantic coast, constructed biomarker mixing models to constrain the amount of fossil carbon in US Mid-Atlantic and Tanzania coastal records, estimated the fossil carbon accumulation rate in coastal sediments and determined the range of global CO 2 release from fossil carbon reservoirs. This work provides evidence for an order of magnitude increase in fossil carbon delivery to the oceans that began ~10–20 kyr after the event onset and demonstrates that the oxidation of remobilized fossil carbon released between 10 2 and 10 4 PgC as CO 2 during the body of the Palaeocene–Eocene Thermal Maximum. The estimated mass is sufficient to have sustained the elevated atmospheric CO 2 levels required by the prolonged global carbon isotope excursion. Even after considering uncertainties in the sedimentation rates, these results indicate that the enhanced erosion, mobilization and oxidation of ancient sedimentary carbon contributed to the delayed recovery of the climate system for many thousands of years.

Nature Geoscience↗
USGS2017

Shallow marine response to global climate change during the Paleocene-Eocene Thermal Maximum, Salisbury Embayment, USA

The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30–100 m water depth) site in the Salisbury Embayment. Observations indicate that at the onset of the PETM, the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low-oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12 C-enriched CO 2 . We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.

Maryland, New Jersey, Pennsylvania, Virginia↗
USGS2017

Biostratigraphic and morphometric analyses of specimens from the calcareous nannofossil genus Tribrachiatus

Biostratigraphic and morphometric analyses of calcareous nannofossil assemblages from one outcrop and two cored sections of lower Eocene sediments reveal the presence of two new species: Tribrachiatus lunatus sp. nov., and Tribrachiatus absidatus sp. nov. Differences between the new species and Tribrachiatus orthostylus are discussed. The first occurrence of the two new species is just below the calcareous nannofossil Zone NP11/NP12 boundary, close to the Chron 24r/23n boundary, and thus they are globally useful biostratigraphic markers.

Journal of Nannoplankton Research↗
USGS2016

Nannoplankton malformation during the Paleocene-Eocene Thermal Maximum and its paleoecological and paleoceanographic significance

The Paleocene-Eocene Thermal Maximum (PETM) is characterized by a transient group of nannoplankton, belonging to the genus Discoaster . Our investigation of expanded shelf sections provides unprecedented detail of the morphology and phylogeny of the transient Discoaster during the PETM and their relationship with environmental change. We observe a much larger range of morphological variation than previously documented suggesting that the taxa belonged to a plexus of highly gradational morphotypes rather than individual species. We propose that the plexus represents malformed ecophenotypes of a single species that migrated to a deep photic zone refuge during the height of PETM warming and eutrophication. Anomalously, high rates of organic matter remineralization characterized these depths during the event and led to lower saturation levels, which caused malformation. The proposed mechanism explains the co-occurrence of malformed Discoaster with pristine species that grew in the upper photic zone; moreover, it illuminates why malformation is a rare phenomenon in the paleontological record.

Paleoceanography↗
USGS2016

Late Paleocene glyptosaur (Reptilia: Anguidae) osteoderms from South Carolina, USA

Heavily tuberculated glyptosaur osteoderms were collected in an active limestone quarry in northern Berkeley County, South Carolina. The osteoderms are part of a highly diverse late Paleocene vertebrate assemblage that consists of marine, terrestrial, fluvial, and/or brackish water taxa, including chondrichthyan and osteichthyan fish, turtles (chelonioid, trionychid, pelomedusid, emydid), crocodilians, palaeopheid snakes, and a mammal. Calcareous nannofossils indicate that the fossiliferous deposit accumulated within subzone NP9a of the Thanetian Stage (late Paleocene, upper part of Clarkforkian North American Land Mammal Age [NALMA]) and is therefore temporally equivalent to the Chicora Member of the Williamsburg Formation. The composition of the paleofauna indicates that the fossiliferous deposit accumulated in a marginal marine setting that was influenced by fluvial processes (estuarine or deltaic). The discovery of South Carolina osteoderms is significant because they expand the late Paleocene geographic range of glyptosaurines eastward from the US midcontinent to the Atlantic Coastal Plain and provide one of the few North American records of these lizards inhabiting coastal habitats. This discovery also brings to light a possibility that post-Paleocene expansion of this group into Europe occurred via northeastward migration along the Atlantic coast of North America.

South Carolina↗
USGS2015

Comparison of three preservation techniques for slowing dissolution of calcareous nannofossils in organic rich sediments

In an attempt to halt or reduce dissolution of calcareous nannofossils in organic and/or pyrite-rich sediments, three different methods of short-term storage preservation were tested for efficacy: vacuum packing, argon gas replacement, and buffered water. Abundance counts of calcareous nannofossil assemblages over a six month period showed that none of the three preservation methods were consistently effective in reducing assemblage loss due to dissolution. In most cases, the control slides made at the drill site had more abundant calcareous nannofossil assemblages than those slides made from sediments stored via vacuum packing, argon gas replacement, or buffered water. Thin section and XRD analyses showed that in most cases, <1% pyrite was needed to drive the oxidation-reduction reaction that resulted in dissolution, even in carbonate-rich sediments.

Georgia, Maryland, North Carolina↗
USGS2013

The Sunny Point Formation: a new Upper Cretaceous subsurface unit in the Carolina Coastal Plain

This paper formally defines the Sunny Point Formation, a new Upper Cretaceous subsurface unit confined to the outer Atlantic Coastal Plain of North and South Carolina. Its type section is established in corehole NH-C-1-2001 (Kure Beach) from New Hanover County, North Carolina. The Sunny Point Formation consists of light-olive-gray to greenish-gray, fine to coarse micaceous sands and light-olive-brown and grayish-red silty, sandy clays. The clay-rich sections typically include ironstone, lignitized wood, root traces, hematite concretions, goethite, limonite, and sphaerosiderites. The Sunny Point Formation is also documented in cores from Bladen County, North Carolina, and from Dorchester and Horry Counties, South Carolina. Previously, strata of the Sunny Point Formation had been incorrectly assigned to the Cape Fear and Middendorf Formations. The Sunny Point occupies a stratigraphic position above the Cenomanian marine Clubhouse Formation and below an upper Turonian unnamed marine unit. Contacts between these units are sharp and unconformable. Calcareous nannofossil and palynomorph analyses indicate that the Sunny Point Formation is Turonian.

North Carolina and South Carolina↗
USGS2011

Drilling the central crater of the Chesapeake Bay Impact Structure: A first look

The late Eocene Chesapeake Bay impact structure is a well‐preserved example of one of Earth's largest impact craters, and its continental‐shelf setting and relatively shallow burial make it an excellent target for study. Since the discovery of the structure over a decade ago [ Edwards et al., 2004; Poag et al., 2004], test drilling by U.S. federal and state agencies has been limited to the structure's annular trough (Figure 1). In May 2004, the U.S. Geological Survey (USGS) drilled the first scientific test hole into the central crater of the Chesapeake Bay impact structure in Cape Charies,Virginia (Figure 1). This partially cored test hole, the deepest to date, penetrated postimpact sediments and impact breccias to a total depth of 823 m.

Chesapeake Bay↗
USGS2010

Inside the crater, outside the crater: Stratigraphic details of the margin of the Chesapeake Bay impact structure, Virginia, USA

Two cores at the outer margin of the Chesapeake Bay impact structure show significant structural and depositional variations that illuminate its history. Detailed stratigraphy of the Watkins School core reveals that this site is outside the disruption boundary of the crater with respect to its lower part (nonmarine Cretaceous Potomac Formation), but just inside the boundary with respect to its upper part (Exmore Formation and a succession of upper Eocene to Pleistocene postimpact deposits). The site of the U.S. Geological Survey-National Aeronautics and Space Administration Langley core, 6.4 km to the east, lies wholly within the annular trough of the crater . The Potomac Formation in the Watkins School core is not noticeably impact disrupted. The lower part of crater unit A in the Langley core represents stratigraphically lower, but similarly undeformed material. The Exmore Formation is only 7.8 m thick in the Watkins School core, but it is over 200 m thick in the Langley core, where it contains blocks up to 24 m in intersected diameter. The upper part of the Exmore Formation in the two cores is a polymict diamicton with a stratified zone at the top. The postimpact sedimentary units in the two cores have similar late Eocene and late Miocene depositional histories and contrasting Oligocene, early Miocene, and middle Miocene histories. A paleochannel of the James River removed Pliocene deposits at the Watkins School site, to be filled later with thick Pleistocene deposits. At the Langley site, a thick Pliocene and thinner Pleistocene record is preserved. © 2010 The Geological Society of America. All rights reserved.

Virginia↗
USGS2009

Paleontological interpretations of crater processes and infilling of synimpact sediments from the Chesapeake Bay impact structure

Biostratigraphic analysis of sedimentary breccias and diamictons in the Chesapeake Bay impact structure provides information regarding the timing and processes of late-stage gravitational crater collapse and ocean resurge. Studies of calcareous nannofossil and palynomorph assemblages in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville A and B cores show the mixed-age, mixed-preservation microfossil assemblages that are typical of deposits from the upper part of the Chesapeake Bay impact structure. Sparse, poorly preserved, possibly thermally altered pollen is present within a gravelly sand interval below the granite slab at 1392 m in Eyreville core B, an interval that is otherwise barren of calcareous nannofossils and dinocysts. Gravitational collapse of watersaturated sediments from the transient crater wall resulted in the deposition of sediment clasts primarily derived from the nonmarine Cretaceous Potomac Formation. Collapse occurred before the arrival of resurge. Low pollen Thermal Alteration Index (TAI) values suggest that these sediments were not thermally altered by contact with the melt sheet. The arrival of resurge sedimentation is identified based on the presence of diamicton zones and stringers rich in glauconite and marine microfossils at 866.7 m. This horizon can be traced across the crater and can be used to identify gravitational collapse versus ocean-resurge sedimentation. Glauconitic quartz sand diamicton dominates the sediments above 618.2 m. Calcareous nannofossil and dinoflagellate data from this interval suggest that the earliest arriving resurge from the west contained little or no Cretaceous marine input, but later resurge pulses mined Cretaceous sediments east of the Watkins core in the annular trough. Additionally, the increased distance traveled by resurge to the central crater in turbulent flow conditions resulted in the disaggregation of Paleogene unconsolidated sediments. As a result, intact Paleogene clasts in Eyreville cores are rare, but clasts of semilithified Potomac Formation silts and clays are common.

Chesapeake Bay↗
USGS2009

The Eocene-Oligocene sedimentary record in the Chesapeake Bay impact structure: Implications for climate and sea-level changes on the western Atlantic margin

A multidisciplinary investigation of the Eocene-Oligocene transition in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville core from the Chesapeake Bay impact basin was conducted in order to document environmental changes and sequence stratigraphic setting. Planktonic foraminifera and calcareous nannofossil biostratigraphy indicate that the Eyreville core includes an expanded upper Eocene (Biozones E15 to E16 and NP19/20 to NP21, respectively) and a condensed Oligocene-Miocene (NP24-NN1) sedimentary sequence. The Eocene-Oligocene contact corresponds to a =3-Ma-long hiatus. Eocene- Oligocene sedimentation is dominated by great diversity and varying amounts of detrital and authigenic minerals. Four sedimentary intervals are identified by lithology and mineral content: (1) A 30-m-thick, smectite- and illite-rich interval directly overlies the Exmore Formation, suggesting long-term reworking of impact debris within the Chesapeake Bay impact structure. (2) Subsequently, an increase in kaolinite content suggests erosion from soils developed during late Eocene warm and humid climate in agreement with data derived from other Atlantic sites. However, the kaolinite increase may also be explained by change to a predominant sediment input from outside the Chesapeake Bay impact structure caused by progradation of more proximal facies belts during the highstand systems tract of the late Eocene sequence E10.Spectral analysis based on gamma-ray and magnetic susceptibility logs suggests infl uence of 1.2 Ma low-amplitude oscillation of the obliquity period during the late Eocene. (3) During the latest Eocene (Biozones NP21 and E16), several lithological contacts (clay to clayey silt) occur concomitant with a prominent change in the mineralogical composition with illite as a major component: This lithological change starts close to the Biozone NP19/20-NP21 boundary and may correspond to sequence boundary E10-E11 as observed in other northwest Atlantic margin sections. It could result from a shift to more distal depositional environments and condensed sedimentation during maximum fl ooding, rather than refl ecting a climatic change in the hinterland. The distinct 1% increase of the oxygen isotopes may correspond to the short-term latest Eocene "precursor isotope event." (4) The abrupt increase of sediment grainsize, carbonate content, and abundance of authigenic minerals (glauconite) across the major unconformity that separates Eocene from Oligocene sediments in the Eyreville core refl ects deposition in shallower settings associated with erosion, winnowing, and reworking. Sediments within the central crater were affected by the rapid eustatic sea-level changes associated with the greenhouse-icehouse transition, as well as by an abrupt major uplift event and possibly enhanced current activity on the northwestern Atlantic margin. ?? 2009 The Geological Society of America.

Chesapeake Bay↗