The delineation of faults that pose seismic risk in intraplate seismic zones and the mapping of features associated with failed rift basins can help our understanding of links between the two. We use new high‐resolution aeromagnetic data, previous borehole sample information, and reprocessed seismic reflection profiles to image subsurface structures and evaluate recent fault activity within the Charleston seismic zone, the associated Mesozoic South Georgia rift basin, and surrounds. The new aeromagnetic data provide an unprecedented view of buried basement structures. NE‐ and NW‐trending lineaments of various lengths throughout the survey area are interpreted as Paleozoic orogenic structures and Mesozoic dikes, respectively. Within the rift basin, 15‐ to 20‐km long ESE‐trending lineaments are associated with faults in pre‐Cretaceous strata of the reflection data and are interpreted as Mesozoic rift structures. Various intersections and terminations of interpreted faults suggest rift‐related reactivation of Paleozoic faults and corresponding inheritance for Mesozoic structures. The reflection data show that several Paleozoic and Mesozoic faults are associated with deformation in Cretaceous and younger sediments, suggesting reactivation in the more recent passive margin setting. Two of these faults, one NE‐striking and one ESE‐striking, are coincident with surficial landforms, suggesting Quaternary slip; the ESE‐striking fault is also well‐aligned with a plan‐view offset in modern seismicity. A favorable orientation for reverse motion on ESE‐striking Mesozoic faults, a possible sub‐basin, and potentially weakened lithosphere are failed rift basin features that may influence intraplate seismicity within the Charleston seismic zone.

Amalgamation of Pangea culminated with zippered N-to-S closing of the Theic ocean during the Alleghanian orogeny. Transpressional-rotational collision produced widespread dextral faulting throughout the eastern Ap-palachian hinterland, and thrust faulting in the western hinterland and foreland. The partially buried southern Appalachian Eastern Piedmont fault system is a product of late Paleozoic transpressional dextral faulting. Eastern Piedmont fault system faults are cut by two 200-190 Ma Central Atlantic Magmatic Province (CAMP) diabase dike sets (similar to NW and N-S), which postdate initial rifting, producing the Late Triassic-Early Jurassic basins. Sinistral reactivation of suitably oriented Paleozoic faults (e.g., Towaliga) that offset Jurassic dikes implies faulting is coeval with CAMP dike emplacement, or occurred very soon after 200-190 Ma dike emplacement. A large NE-striking sinistral fault (Estill fault) offsets magnetic and gravity highs in the Brunswick (Charleston) terrane in South Carolina and Georgia. This fault is at least 185 km long, with ca. 75-80 km maximum of sinistral separation. The Estill fault geometry agrees with the stress field associated with Central Atlantic Magmatic Province dike emplacement. We conclude that movement along the Estill and other sinistral faults represents Early Jurassic displacement that is well documented in eastern North America prior to Atlantic opening. The early Mesozoic post-failed rifting (basin formation) preceded dike emplacement and pre-spreading sinistral faulting. We recognize four stages in the Late Triassic-Jurassic tectonics and kinematics of eastern North America based on field, crosscutting relationships, and available geophysical data: (1) initial W-to-E failed transtensional rifting with formation of the S-to-N-younging Triassic-Jurassic basins; (2) CAMP diabase dikes intruded 200-190 Ma; (3) sinistral movement of large blocks of crust in the North Atlantic region including southeastern North America; and (4) spreading and opening of the Atlantic Ocean 195-170 Ma. These stages mark the reversal of Alleghanian rotational dextral transpressional (zippered) collision forming Pangea supercontinent and 'unzip-ping' the supercontinent prior to Atlantic opening.

What Is the Issue? Professional dental care is important to help maintain oral health. Routine dental cleaning usually includes both scaling and polishing. Scaling is the removal of plaque and tartar from the crown and root surfaces of teeth. Polishing is the removal of residual plaque and external stains from the teeth. To support decisions about the optimal components for professional dental cleaning, it is important to understand the potential benefits and harms of routine dental polishing when compared to no routine dental polishing. What Did We Do? We searched for clinical and cost-effectiveness literature comparing routine dental polishing with no routine dental polishing. We also looked for evidence-based guidelines that provide recommendations about the use of routine dental polishing for the maintenance of oral health in adults and children. An information specialist conducted a search of peer-reviewed and grey literature sources published between January 1, 2018, and September 28, 2023. Documents were excluded if we could not isolate the effects of dental polishing from other dental procedures or if polishing techniques were used for a purpose other than the routine polishing of teeth. What Did We Find? We did not find any studies directly evaluating the clinical or cost-effectiveness of routine dental polishing versus no routine dental polishing, or guidelines about the use of routine dental polishing, that met the inclusion criteria for this review. We identified limited literature that examines the combined effects of routine scaling and polishing. Research is needed that distinguishes the effects of routine dental polishing from the effects of other dental procedures. What Does This Mean? Without comparative clinical or cost-effectiveness evidence about routine dental polishing versus no routine dental polishing, decision-makers may also wish to consider that patients value routine scaling and polishing, and that the cost of dental care may be a barrier to visiting the dentist for some people. New polishing methods, such as air powder polishing, may also be useful to consider when making decisions about routine polishing to support dental health. These methods include some of the benefits of scaling and may present opportunities to reduce periodontal inflammation or the length of a dental appointment.

First posted March 18, 2022 For additional information, contact: Florence Bascom Geoscience CenterU.S. Geological SurveyMail Stop 926A12201 Sunrise Valley DriveReston, VA 20192Contact Pubs Warehouse This 1:100,000-scale geologic map of the South Boston 30' × 60' quadrangle, Virginia and North Carolina, provides geologic information for the Piedmont along the I–85 and U.S. Route 58 corridors and in the Roanoke River watershed, which includes the John H. Kerr Reservoir and Lake Gaston. The Raleigh terrane (located on the eastern side of the map) contains Neoproterozoic to early Paleozoic(?) polydeformed, amphibolite-facies gneisses and schists. The Carolina slate belt of the Carolina terrane (located in the central part of the map) contains Neoproterozoic metavolcanic and metasedimentary rocks at greenschist facies. Although locally complicated, the slate-belt structure mapped across the South Boston map area is generally a broad, complex anticlinorium of the Hyco Formation (here called the Chase City anticlinorium) and is flanked to the west and east by synclinoria, which are cored by the overlying Aaron and Virgilina Formations. The western flank of the Carolina terrane (located in the western-central part of the map) contains similar rocks at higher metamorphic grade. This terrane includes epidote-amphibolite-facies to amphibolite-facies gneisses of the Neoproterozoic Country Line complex, which extends north-northeastward across the map. The Milton terrane (located on the western side of the map) contains Ordovician amphibolite-facies metavolcanic and metasedimentary gneisses of the Cunningham complex.Crosscutting relations and fabrics in mafic to felsic plutonic rocks constrain the timing of Neoproterozoic to late Paleozoic deformations across the Piedmont. In the eastern part of the map, a 5- to 9-kilometer-wide band of tectonic elements that contains two late Paleozoic mylonite zones (Nutbush Creek and Lake Gordon) and syntectonic granite (Buggs Island pluton) separates the Raleigh and Carolina terranes. Amphibolite-facies, infrastructural metaigneous and metasedimentary rocks east of the Lake Gordon mylonite zone are generally assigned to the Raleigh terrane. In the western part of the map area, a 5- to 8-kilometer-wide band of late Paleozoic tectonic elements includes the Hyco and Clover shear zones, syntectonic granitic sheets, and amphibolite-facies gneisses along the western margin of the Carolina terrane at its boundary with the Milton terrane. This band of tectonic elements is also the locus for early Mesozoic extensional faults associated with the early Mesozoic Scottsburg, Randolph, and Roanoke Creek rift basins.The map shows fluvial terrace deposits of sand and gravel on hills and slopes near the Roanoke and Dan Rivers. The terrace deposits that are highest in altitude are the oldest. Saprolite regolith is spatially associated with geologic source units and is not shown separately on the map.Mineral resources in the area include gneiss and granite quarried for crushed stone, tungsten-bearing vein deposits of the Hamme district, and copper and gold deposits of the Virgilina district. Surface-water resources are abundant and include rivers, tributaries, the John H. Kerr Reservoir, and Lake Gaston. Groundwater flow is concentrated in saprolite regolith, along fractures in the crystalline bedrock, and along fractures and bedding-plane partings in the Mesozoic rift basins.

ABSTRACT The moment magnitude (Mw) ∼7 earthquake that struck Charleston, South Carolina, on 31 August 1886 is the largest historical earthquake in the United States east of the Appalachian Mountains. The fault(s) that ruptured during this earthquake has never been conclusively identified, and conflicting fault models have been proposed. Here we interpret reprocessed seismic reflection profiles, reprocessed legacy aeromagnetic data, and newly collected ground penetrating radar (GPR) profiles to delineate faults deforming the Cretaceous and younger Atlantic Coastal Plain (ACP) strata in the epicentral area of the 1886 earthquake. The data show evidence for faults folding or vertically displacing ACP strata, including apparent displacements of near-surface strata (upper ∼20 m). Aeromagnetic data show several northeast (NE)-trending lineaments, two of which correlate with faults and folds with vertical displacements as great as 55 m on the seismic reflection and radar profiles. ACP strata show only minor thickness changes across these structures, indicating that much of the displacement postdates the shallowest well-imaged ACP strata of Eocene age. Faults imaged on the seismic reflection profiles appear on GPR profiles to displace the erosional surface at the top of the upper Eocene to Oligocene Cooper Group, including where railroad tracks were bent during the 1886 earthquake. Some faults coincide with changes in river trends, bifurcations of river channels, and unusual river meanders that could be related to recent fault motion. In contrast to our interpreted NE fault trends, earthquake locations and some focal mechanisms in the modern seismic zone have been interpreted as defining a nearly north-striking, west-dipping zone of aftershocks from the 1886 earthquake. The relationship between the modern seismicity and the faults we image is therefore enigmatic. However, multiple faults in the area clearly have been active since the Eocene and deform strata in the upper 20 m, providing potential targets for field-based geologic investigations.

High-pressure minerals provide records of processes not normally preserved in Earth's crust. Reidite, a quenchable polymorph of zircon, forms at pressures >20 GPa during shock compression. However, there is no broad consensus among empirical, experimental, and theoretical studies on the nature of the polymorphic transformation. Here we decipher a multistage history of reidite growth recorded in a zircon grain in distal impact ejecta (off-shore northeastern United States) from the ca. 35 Ma Chesapeake Bay impact event which, remarkably, experienced near-complete conversion (89%) to reidite. The grain displays two distinctive reidite habits: (1) intersecting sets of planar lamellae that are dark in cathodoluminescence (CL); and (2) dendritic epitaxial overgrowths on the lamellae that are luminescent in CL. While the former is similar to that described in literature, the latter has not been previously reported. A two-stage growth model is proposed for reidite formation at >40 GPa in Chesapeake Bay impact ejecta: formation of lamellar reidite by shearing during shock compression, followed by dendrite growth, also at high pressure, via recrystallization. The dendritic reidite is interpreted to nucleate on lamellae and replace damaged zircon adjacent to lamellae, which may be amorphous ZrSiO4 or possibly an intermediate phase, all before quenching. These results provide new insights on the microstructural evolution of the highpressure polymorphic transformation over the microseconds-long interval of reidite stability during meteorite impact. Given the formation conditions, dendritic reidite may be a unique indicator of distal ejecta.

JERSEY, USA: A HALLMARK OF DISTAL IMPACT EJECTA? A. J. Cavosie, M. B. Biren, K. V. Hodges, J.-A. Wartho, J. W. Horton, Jr., and C. Koeberl, Space Science and Technology Centre and the Institute for Geoscience Research, School of Earth and Planetary Science, Curtin University, Perth, Australia, School of Earth and Space Exploration, Arizona State University, Tempe, AZ USA, GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany, U.S. Geological Survey, National Center, Reston, VA, USA, Department of Lithospheric Research, University of Vienna, Vienna, Austria. Corresponding author: aaron.cavosie@curtin.edu.au

Single crystal (U-Th)/He dating has been undertaken on 21 detrital zircon grains extracted from a core sample from Ocean Drilling Project (ODP) site 1073, which is located similar to 390 km northeast of the center of the Chesapeake Bay impact structure. Optical and electron imaging in combination with energy dispersive X-ray microanalysis (EDS) of zircon grains from this late Eocene sediment shows clear evidence of shock metamorphism in some zircon grains, which suggests that these shocked zircon crystals are distal ejecta from the formation of the similar to 40 km diameter Chesapeake Bay impact structure. (U-Th/He) dates for zircon crystals from this sediment range from 33.49 +/- 0.94 to 305.1 +/- 8.6 Ma (2 sigma), implying crystal-to-crystal variability in the degree of impact-related resetting of (U-Th)/He systematics and a range of different possible sources. The two youngest zircon grains yield an inverse-variance weighted mean (U-Th)/He age of 33.99 +/- 0.71 Ma (2 sigma uncertainties n = 2; mean square weighted deviation = 2.6; probability [P] = 11%), which is interpreted to be the (U-Th)/He age of formation of the Chesapeake Bay impact structure. This age is in agreement with K/Ar, 40Ar/39Ar, and fission track dates for tektites from the North American strewn field, which have been interpreted as associated with the Chesapeake Bay impact event.