Predicting and characterizing the subsurface remains a key endeavor for applied geoscientists. Biostratigraphy provides critical support through its ability to support correlation within the subsurface and to determine depositional environments of sedimentary rock units. A combination of time-based correlation and paleoenvironmental interpretation under the umbrella of sequence stratigraphy helps organize stratigraphic information and allows for predictions to be made as to the sedimentary successions and their character that can be expected between data-points and in data-poor regions. Issues that can be typically resolved by biostratigraphy occur at a wide variety of scales and – in decreasing order of scale – include generation of play concepts and global- and basin-scale play screening through support of correlation, Earth systems science context (e.g. paleoclimate, eustasy), gross depositional environment mapping, and sequence stratigraphy; age frameworks for basin modelling; appraising assets; and the effective, efficient and safe exploitation of assets through operational biostratigraphy including casing/coring picks and biosteering. Applied biostratigraphy has supported the ongoing efforts of the oil and gas industry for over one hundred years and the lessons from these endeavors can be applied to alternative subsurface use cases, including storage, defining optimal locations for low-carbon energy sources such as geothermal, and for engineering projects associated with, for example, wind-farm location. Importantly, biostratigraphic data is suitable for assisted interpretation arising from the digital revolution, meaning that data gathering and interpretation are becoming faster and better integrated.
The upper Claiborne, Jackson, and Vicksburg groups record approximately 13 Ma of deposition within the upper Paleogene section of Mississippi (middle Eocene through lower Oligocene). These strata are characterized by repeated suites of siliciclastic and carbonate lithologies, including sandy, glauconite-bearing shell beds and marls exposed updip (in outcrop), and thick limestones that developed across a downdip paleo-high. These carbonate strata are well known from subsurface mapping efforts, but their significance remains largely unexplored in outcrop-based stratigraphic and paleontological studies. Here, we review and integrate subsurface data from well log and core studies with field-based observations to propose a new, mixed carbonate-siliciclastic depositional model for the upper part of the Paleogene section of Mississippi. Deltaic strata overlie widespread basin-margin unconformities but thin distally to condensed marine shales across the Wiggins Arch. Accordingly, these beds reflect lowstands in sea level and were deposited through the regressive outbuilding of the shoreline into the Mississippi Interior Salt Basin. Glauconitic shell beds occur in association with coastal barrier systems, where they reflect the transgressive reworking of previously deposited sand and bioclastic material. In contrast, carbonate sediments are interpreted to have formed in response to the onshore trapping of siliciclastics, coupled with enhanced carbonate production during relative highstands in sea level. These are characterized by successive foraminiferal-algal grain banks in the subsurface, which thin and grade landward to mollusk-rich shelf mudstone-wackestones (marl and limestone units) in outcrop. Notably, both carbonates and glauconitic shell beds appear to broadly record marine transgression but are expressed differently based on relative shoreline position within major base-level cycles. This model differs from the predominantly siliciclastic style of deposition that characterizes the present-day northern Gulf margin and appears to lack a strong modern analog. It also provides a basis for refined stratigraphic interpretation, with important caveats to sequence stratigraphic models commonly applied in this section, and establishes a framework in which to analyze late Paleogene faunas in the context of evolving, process-related depositional environments.
Dinoflagellate cyst palynology and lithostratigraphy from three continuously cored boreholes (Blackbird, Smyrna, and Woodland Beach), supplemented by calcareous nannofossil biostratigraphic data, were used to refine the age and correlation of three Paleocene-Eocene formations in northern Delaware: the Vincentown, Manasquan, and Shark River. Lithologic logs reveal significant facies changes in the upper Paleocene Vincentown Formation over a short distance (*9 km) southeastward, transitioning from very permeable glauconite-quartz-shell-rich sands that form the regionally important Rancocas/Aquia aquifer to much less permeable muddy sands and sandy muds. These lithologic changes represent a shift from nearshore, clear, warm-water, carbonate-rich sand shoals to mud-dominated deeper-water, offshore shelfal environments. Dinocyst assemblages including Areoligera gippingensis, Cribroperidinium giuseppei, and Stenodinium meckelfeldensis confirm the Paleogene ages and track these paleoceanographic changes from shallow coastal settings updip to neritic or outer marine settings downdip. The Vincentown Formation is unconformably overlain by the lower Eocene Manasquan Formation, which consists predominantly of silt and clay with relatively consistent lithology across the study area, representing general neritic or open marine conditions. Lithology, dinoflagellate cyst assemblages, and calcareous nannofossil data indicate that the Marlboro Clay and its record of the onset of the Paleocene-Eocene Thermal Maximum (PETM) global warming event is absent from the Paleocene-Eocene transition at these sites, with an unconformity marking the boundary between the Vincentown and Manasquan formations. The youngest unit examined, the Eocene Shark River Formation, unconformably overlies the Manasquan Formation and consists of interbedded clayey silts and sands, with dinoflagellate assemblages suggesting a return to coastal or inner neritic settings. Calcareous nannofossil zones recognized from the Woodland Beach core corroborate the depositional ages determined using dinoflagellates throughout the sequence, confirming the chronostratigraphic framework for these important coastal plain units.
This study revises the lithostratigraphic framework of the Upper Devonian interval traditionally assigned to the Greenland Gap Group across the central Appalachian Valley and Ridge Province. The work aims to modernize and standardize lithostratigraphic nomenclature, establish a new reference section and demonstrate how the revised stratigraphy improves edge-matching of 1:24,000 scale geologic maps and supports compilation mapping at scales of 1:100,000 and larger. The revision eliminates the names Greenland Gap Group, Scherr Formation and the Minnehaha Springs Member of the Scherr Formation; reassigns all strata previously designated as Scherr Formation by Dennison (1970) to the upper Brallier Formation; and abandons the basal Mallow Member of the Foreknobs Formation, placing its strata within the upper Brallier as originally defined by Butts (1918). The contact between the Brallier and Foreknobs formations is placed at the base of the first mappable, ridge-forming package of fine-to coarse-grained, cross-bedded, sandstone beds, often containing rounded quartz pebbles with minor interbeds of shale and siltstone. This contact may be gradational in places but, even in absence of good exposure, can usually be distinguished topographically in recently produced lidar-derived imagery as having elevated relief due to the presence of more resistant, compositionally mature coarse-grained sandstone-rich strata. Applying this criterion for mapping the contact between the Brallier and Foreknobs formations has resulted in reconciliation of mismatches of geologic contacts along several 7.5-minute quadrangle boundaries in the states of Virginia, West Virginia, Maryland and Pennsylvania. A new reference section at Baker, West Virginia showcases the contacts between the Harrell Shale, Brallier Formation, Foreknobs Formation and Hampshire Formation. A digital outcrop model of the reference section is provided for future preservation.
This study presents the first detailed biostratigraphic analysis of calcareous nannofossils and Alveolina assemblages from the Mojen section in the Alborz Zone, North Iran. By integrating Alveolina distribution with nannofossil biozones, the research shows that the NP10 (CNE3) to NP12 (CNE4) zones correspond to the Shallow Benthic Zones SBZ8-SBZ10, representing an early Ypresian age (upper middle Ilerdian to early Cuisian). Furthermore, Alveolina citrea (Drobne) has a longer biostratigraphic range in Turkey and Iran, extending into younger strata within the SBZ7-SBZ9 interval and aligning with the NP zones, highlighting its widespread occurrence across the western-central Neo-Tethys.
The Fahliyan Formation (Lower Cretaceous, Berriasian-Hauterivian) in the Zagros Basin of southwest Iran represents one of the most significant shallow-marine carbonate successions along the northeastern margin of the Arabian Plate. Detailed microfacies analysis of two subsurface stratigraphic wells (Aghar-19 and Dey-2) reveals a spectrum of 12 microfacies ranging from tidal-flat to open-marine settings. These microfacies include dolo-wackestone, stromatolite boundstone, algal intraclast wackestone foraminifer bioclast wackestone, Trocholina bioclast wackestone, Fine ooidal peloidal grainstone, coarse ooidal peloidal grainstone, intraclast ooidal grainstone, coral boundstone, bioclast packstone, bioclast wackestone, and sponge spicule bioclast wackestone, reflecting deposition across supratidal, tidal flat, lagoon, reef, fore-shoal, and slope environments. Vertical distribution of the facies demonstrates variations in paleobathymetry between the studied sections, with higher proportions of skeletal grains in the upper Aghar-19 well (-47%) and mid Dey-2 well (-50%). The abundance of skeletal components, particularly corals, benthic foraminifera, and calcareous algae, indicates favorable paleoecological conditions with sufficient light, nutrients, and normal salinity during the Early Cretaceous. These findings highlight the influence of the Late Cimmerian tectonic movements and basement faults on carbonate platform development and depositional architecture. Overall, the integrated microfacies and stratigraphic data provide new insights into the paleogeography and paleobathymetry of the Early Cretaceous Zagros Basin and underscore the significance of the Fahliyan Formation as a potential hydrocarbon reservoir.
Detailed field and stratigraphic studies were undertaken on the Upper Cretaceous-lower Paleogene (K-Pg) pre-rift sequences at the Duwi Mountain Range (DMR), Quseir Area, Red Sea Coast, Egypt. Six stratigraphic sections were investigated to cover the DMR. They are arranged in a south-north profile as follows: Gabal Hamadat, Nasser Mine, Beida Mine, Gabal Anz, Gabal Nakheil and Wadi Sudmeen. The studied pre-rift (Red Sea Rift) succession is lithostratigraphically represented by the Duwi (uppermost part), Dakhla, Tarawan, Esna, and Thebes (lowermost part) formations. Biostratigraphically, twenty-one global planktonic foraminiferal zones were defined. Three syn-sedimentary tectonic events were recorded, the first and second tectonic events (TE I and TE II) were regional and lie within the Duwi/Dakhla and the uppermost part of the Hamama Member. The TE I occurred at the Campanian/Maastrichtian (C/M) boundary, whereas the TE II occurred at the beginning of the Danian. TE III was local and is recorded only at Wadi Sudmeen within the Beida Member in the latest Danian. These events were related to the Syrian-Arc Event, which caused the uplift of the DMR as paleo-highs during this interval.
The Eocene to Oligocene Nisai Formation in the Khuzhobai Section, Pishin Belt (Balochistan, SW Pakistan), was investigated to determine its microfacies, depositional environments, and burial history. A visual estimation technique is used to quantify different allochemical constituents and discriminate microfacies. A total of eight microfacies were identified in the limestone unit of the Nisai Formation through detailed microfacies analysis. The identified microfacies represent deposition of the Nisai Formation in a carbonate ramp setting, including inner, middle, and outer ramp environments. The lagoonal facies in the inner ramp setting is characterized by imperforate foraminifera such as miliolids and Alveolina and abundant coralline red algae. The middle ramp facies are characterized by abundant Nummulites, Assilina, and coralline red algae, together with a rare to sparse amount of shallow marine fauna including gastropods, echinoderms, and ostracods. The outer ramp facies is characterized by planktonic foraminifera and mudstone depositional texture. Based on the comparison of larger benthic foraminifera (LBF) assemblages, microfacies characteristics, and mixing of faunas in the middle ramp setting, a mixed carbonate-siliciclastic, storm-dominated homoclinal ramp depositional model is suggested for the Nisai Formation. The studied formation has been altered by various diagenetic processes, which occurred in different diagenetic environments, including the marine, meteoric-phreatic, and burial environments. The early marine diagenetic environment is indicated by features such as burrowing, micritization, and grain packing, whereas the meteoric-phreatic environment is evidenced by processes like inversion neomorphism, dissolution, drusy and granular mosaic calcite cements, as well as the presence of pendant and meniscus cements. The burial phase is evident from the aggrading neomorphism, further mechanical grains packing, fracturing, and stylolitization, followed by a minor phase of uplift and unroofing. Visible secondary porosity in the Nisai Formation has been significantly enhanced by dissolution within the meteoric-phreatic diagenetic environment.
This study focuses on planktic foraminifera to interpret the paleoecology and paleogeography of the uppermost 20 m of the Tanjero Formation below the Cretaceous/Paleogene (K/Pg) boundary of the Kurdistan Region, northeastern Iraq. In the lower part of the studied section, which was deposited in deep water (more than 100 m), the planktic foraminifera species with double-keeled tests Abathomphalus, Marginotruncana, Globotruncana, Gansserina, and Rugotruncana (Morphotype 3), are predominant. The middle part of the section is characterized by abundant species from the Globotruncanella and Globotruncanita genera, which have a single-keeled test, representing deposition in intermediate water (50-100 m depth) (Morphotype 2). The upper part of the section is marked by an abundance of genera with a nonkeeled test, including Hedbergella, Heterohelix, Pseudoguembelina, Pseudotextularia, Guembelitria, Planoheterohelix, Rugoglobigerina, Globigerinelloids Plummerita, and Rugotruncana, which are indicators of shallower water (approximately 50 m depth) (Morphotype 1). The diverse planktic foraminifera genera in this section are typical of Tethyan provinces, suggesting a stable, mesotrophic environment. The planktic foraminiferal assemblage from the uppermost part of the formation suggests paleoceanographic conditions that favored opportunistic organisms. This is evidenced by the presence of the genus Pseudoguembelina, a successful surface and subsurface dweller in tropical and subtropical open oceans with warm and oligotrophic surface waters. The expansion of this strongly photosymbiotic genus is attributed to favorable palaeoecological conditions in the Late Cretaceous oceans. The results obtained imply the presence of a well-stratified water column, a tropical to subtropical climate, and deposition in the outer shelf to upper bathyal environments. These conditions account for the presence of well-preserved and highly diversified Maastrichtian foraminifer assemblages of the globotruncanid species, which include: Hedbergella, Praeglobotruncana, Marginotruncana, Globotruncana, Contusotruncan, Globotruncanita, Archaeoglobigerina, Rugoglobigerina,
The Cenomanian-Turonian (ca. 94 Ma) interval of the Western Interior Seaway (WIS) of North America hosts a critical record of changing marine shelf environments during greenhouse conditions. In this paper, we compile a detailed study of lithofacies, calcareous nannofossil biostratigraphy and elemental geochemistry from outcrops and cores of mid-Cenomanian to lower Turonian strata in Kansas, eastern Nebraska, and western Iowa, along the understudied eastern margin of the WIS. The Graneros Shale was constrained as a generally non-calcareous heterolithic unit deposited in vigorous bottom waters. We suggest that the contact between the Graneros Shale and overlying Greenhorn Limestone can be readily identified with a shift to more calcareous lithofacies, increase in Ca/Al and increase in calcareous nannofossil recovery. The uppermost unit of the Greenhorn, the Bridge Creek Limestone, was noted by widespread chalk deposition. Our combined use of lithofacies, biostratigraphy and elemental chemostratigraphy provides better constraint on these units on the eastern margin of the WIS, especially for units in which contacts are currently uncertain due to their gradational nature. Our results provide a more detailed assessment of depositional environments along the eastern margin of the WIS and improved comparison to the western margin. We show that, during Graneros time, there was substantial detrital sediment input from the North American Craton to the east. The transition towards pelagic carbonate sedimentation, especially in northeastern Nebraska, and a concomitant decline in detrital sediment, may have resulted from rising eustatic sea level and the transgressive landward retreat of detrital facies tracts, unconstrained changes in shelf currents or physiography and/or changes in climate that decreased detrital sediment delivery during the late Cenomanian to early Turonian. We also show that the critical Oceanic Anoxic Event 2 (OAE2) was captured in our studied sections. Along the eastern margin of the seaway, OAE2 corresponds to overall dry climate conditions, widespread chalk deposition and possible bottom water dysoxia. Such records have been lacking from nearshore shelf settings, especially in the eastern margin of the WIS, and the discovery opens future research that can better constrain the event in neritic environments.
The diatom biochronology of ODP (Ocean Drilling Program) Holes 682A and 688E provides a detailed framework for refining Miocene diatom zonation in the East Pisco Basin of southern Peru, establishing both a nearly complete offshore reference section and a correlation tool for the fragmentary onshore vertebrate-bearing deposits. This new biostratigraphic record documents a complete succession of low latitude and/or northeastern Pacific Miocene diatom zones, with two notable exceptions: a dissolution and/or hiatus interval (-16.5-14 Ma) during the Middle Miocene Climatic Optimum and a likely earliest Miocene hiatus (-23.4-21.8 Ma). Although eastern equatorial Pacific diatom zones characterize the Upper Oligocene and Lower Miocene strata, an increased abundance of cool-water diatoms that lived during the Middle and Late Miocene allows better application of northeast Pacific diatom zones, except during the Messinian (7-6 Ma) when warm-water diatoms predominate. The effects of eustatic sea level and tectonics on depositional sequences in the EPB and in offshore cores off central Peru are discussed.
Facies analysis and sequence stratigraphic interpretation of the Upper Cretaceous-lower Paleocene succession cropping out in the Gafsa Basin provide new information on sediment cyclicity and paleoclimatic conditions. Mixed carbonate-siliciclastic deposits of the Haria Formation show six principal facies that were deposited in a shallow marine environment; these are summarized in a homoclinal ramp model that formed during a humid climate in the Late Cretaceous followed by cooler and dryer climate in the early Paleocene. The mixed (carbonate and siliciclastic) deposits of the Haria Formation and are grouped into six facies associations. Carbonate facies described for the first time in the Haria Formation are considered as a new facies in this formation represented by channel deposits and lumachellic limestones. Four depositional zones are recognized on the Haria ramp: 1) basinal, outer ramp (deep water associations); 2) mid ramp (infratidal to subtidal associations); 3) inner ramp (intertidal to supratidal associations); and 4) lagoon facies associations. The mineralogical assemblages are generally indicative of a hot and humid climate with contrasting seasonal change during the Late Cretaceous and have a predominance of smectite, illite and kaolinite clay minerals associated with calcite, quartz and dolomite. This warm climate then become colder and dryer the early Paleocene and was characterized by a significant increase in kaolinite and illite. Nine stratigraphic units are interpreted as depositional sequences showing retrogradational (lowstand systems tract), aggradational (transgressive systems tract) and progradational (highstand systems tract) packages of facies associations. These depositional sequences were controlled by small-scale relative sea-level cycles. These changes in stacking patterns (cycle thickness, cycle type, and facies proportion) allow for reconstruction of long-term sea level trends.
The Pliocene Yorktown Formation, deposited on the U.S. Mid-Atlantic Coastal Plain, has played an important role in advancing our knowledge of Pliocene paleoclimate. To refine the age and paleoenvironment of the Yorktown Formation, we analyzed the calcareous nannofossil assemblage and compared it with variations in lithology and calculated sea surface temperature (SST) from previous studies. The Yorktown Formation in the studied sections consists of, in ascending order, the Sunken Meadow, Rushmere, Morgarts Beach, and Moore House members. Sediment samples were collected from these units and analyzed for calcareous nannoplankton assemblages. The last occurrences of both Reticulofenestra pseudoumbilicus (3.82 Ma) and Sphenolithus spp. (3.61 Ma) were recognized within the Sunken Meadow Member. Discoaster tamalis and Discoaster surculus sporadically occurred within the Rushmere Member, but no specimens of the genus Sphenolithus were recorded, suggesting that this unit was deposited sometime between 3.61-2.76 Ma. Rare occurrences of the genus Discoaster made it difficult to constrain the age of the Morgarts Beach and Moore House members, but they are most likely deposited before re-entrance of small Gephyrocapsa (ca. 2.5 Ma), supporting previous age estimates based on planktic foraminiferal biostratigraphy and variation in alkenone-based sea-surface temperature estimates. The abrupt decline of both cold-water species (Coccolithus pelagicus) and coastal species (Helicosphaera spp.) is associated with a rise in SST within the Rushmere Member just below the Morgarts Beach Member, and it may reflect a rapid transgression following the global sea-level low stand associated with Marine Isotope Stage (MIS)M2.
Middle Cretaceous carbonates of the Sarvak Formation, as its stratigraphic equivalents across the Persian Gulf, are of primary importance in the late Mesozoic petroleum systems, representing one of the most significant hydrocarbon reservoirs in the Middle East. Based on petrographic examination of the samples collected from this rock unit, 10 microfacies are recognized, indicating deposition in lagoon, shoal/rudist build-up, slope, and basin settings. The vertical distribution of microfacies belts suggests that the Sarvak Formation in southeastern Persian Gulf was deposited on a carbonate ramp and/or a low-gradient rimmed shelf. Stratigraphic distribution pattern of micro- and macrofauna in the sequences examined allows for the recognition of three biozones and two biofacies, collectively corroborating a late Albian-late Cenomanian age. Additionally, recognition of sequence boundaries and maximum flooding surfaces based on combined petrographic and petrophysical data obtained from 11 subsurface sections points to the presence of three third-order sequences within the Sarvak Formation. Frequency analysis and thickness variations in the identified facies and sedimentary sequences reveal significant changes in the thickness of the Sarvak Formation. These changes are attributed to combined effects of regional tectonic activity and eustatic sea-level fluctuations. The reactivation of basement faults alongwith halokineticmovementswere significant tectonic factors influencing depositional thickness during the middle Cretaceous in the study area, as clearly evident in the 2D seismic profiles. Tectonic factors during Cenomanian, along with eustatic sea-level fluctuations, resulted in widespread erosional disconformities that are traceable in nearly all subsurface stratigraphic sections studied. The Cenomanian-Turonian boundary is identified as a significant paleoexposure surface, exhibiting evidence of karstification, leaching, and vuggy porosity in uppermost part of the Sarvak Formation.
Anthropogenic climate change is an existential threat to our planet, impacting everything from the delicate balance of ecosystems to the availability of vital resources. Coastal regions, particularly vulnerable to the impacts of climate change due to rising sea levels and changing weather patterns, are experiencing increased erosion, flooding, and habitat loss. Understanding how coastal regions responded to past warming is crucial for developing effective adaptation and mitigation strategies. One past interval commonly used to examine and compare with climate model projections of near future conditions is the mid-Piacenzian Warm Period (MPWP) which occurred between*3.3 and 3.0 Ma. Here we review the stratigraphy of Atlantic Coastal Plain (ACP) sediments to determine the stratigraphic position of the MPWP by evaluating ages based upon existing and new planktic foraminifer occurrence data calibrated to the current geologic time scale (GTS2020). We identify geologic formations representing pre-, syn-, and post-MPWP environments. The Sunken Meadow Member of the Yorktown Formation in Virginia and North Carolina and the Wabasso beds in the subsurface of Georgia and Florida both fall within Planktic Foraminiferal Zone PL1 and represent pre-MPWP Pliocene deposits. Parts of the Yorktown Formation in southeastern Virginia and northern North Carolina, the Duplin Formation in North Carolina and South Carolina, and the Raysor Formation in South Carolina and Georgia, fall within Planktic Foraminiferal Zone PL3 and were deposited following a major regression associated with a global drop in sea level during Marine Isotope Stage (MIS) M2 and represent syn-MPWP deposits. Representing the immediately post-MPWP climate conditions (Planktic Foraminiferal Zone PL5) are the Chowan River, Bear Bluff, and Cypresshead Formations. This work provides a record of the MPWP from Georgia to Virginia and provides a stratigraphic framework within which the impacts of a profound global warming on the east coast of the United States can be assessed.
Contradictory interpretations of upper Pleistocene (120–40 ka) sedimentary deposits along the US Mid-Atlantic Coast have hindered the development of a reliable regional sea-level curve for the last glacial cycle. This study presents new and compiled sediment cores, ground-penetrating radar, topographic data, aerial imagery, and limited geochronology from geologic units emplaced along the ocean-facing side of the Virginia Eastern Shore during mid- and late-Pleistocene periods of higher-than-present relative sea level: the Accomack Member (Omar Formation), the Butlers Bluff Member (Nassawadox Formation), the Joynes Neck Sand, and the Wachapreague Formation. Minor lithologic and morphologic updates are presented for the MIS 5e/5c Butlers Bluff Member, which is interpreted as a southward-prograding spit emplaced atop penecontemporaneous shoreface sediments or older transgressive sediments which fill the Exmore Paleochannel. The Joynes Neck Sand is reinterpreted as a coastal lag deposit, correlated with the Ironshire Formation in Maryland and Delaware, likely emplaced during MIS 5c. The Wachapreague Formation is determined to be a composite unit composed of two newly mapped members—the Locustville and Upshur Neck—which differ in lithology, internal architecture, and surficial morphology. The older and western Locustville Member (MIS 5a) is characterized by progradational beach and foredune ridges built atop transgressive shoreface and backbarrier deposits, and is correlated with the Sinepuxent Formation in Maryland and Delaware. The younger and eastern Upshur Neck Member of the Wachapreague Formation (late MIS 5a) is distinguished by surficial recurved ridges and preserved washover, dune, and channel-fill structures associated with spit growth atop shoreface deposits. These findings indicate that the Wachapreague Formation was constructed during two sequential highstands: an initial phase of sea-level rise and then fall allowed for deposition of the Locustville Member as a transgressive-highstand-regressive barrier system; and, following a period of lower-than-present sea level, a later highstand resulted in partial erosion of the easternmost Locustville and growth of the Upshur Neck Member. Finally, we update earlier descriptions of an aeolian sand sheet, likely deposited during MIS 3c, that discontinuously overlies most of the east-central Virginia Eastern Shore. Together, these findings update interpretations of the depositional history of the southern Delmarva Peninsula, and allow for future refinement of the sea-level history of the last interglacial-to-glacial period along the mid-field US Mid-Atlantic coast.
Foraminifera, ostracod and calcareous nannofossil contents of the Cenomanian-Santonian succession are integrated to enhance and refine biostratigraphic divisions and age determinations in the Abu Sennan oil field, Abu Gharadig basin, North Western Desert, Egypt. Foraminiferal (seven), ostracod (eleven) and calcareous nannofossil (seven) zones were identified and correlated with international and local zonal schemes. The boundary of the Santonian age (within Khoman Formation) is delineated by the first appearance of the foraminifera Dicarinella concavata and D. canaliculata; the ostracod Brachycythere angulata and the calcareous nannofossil Zeugrhabdotus scutula and Lithastrinus septenarius. The Campanian age of Khoman B is not recorded due to the existence of a local unconformity surface. The Coniacian–Santonian boundary (top Abu Roash AMember) is characterized by the first appearance of the foraminifera Discorbis turonicus, D. minutum and D. simplex, the ostracodHermanites juxi, Oertliella? dextrospinata, and Cythereis cretaria and the calcareous nannofossil species Quadrum intermedium. The Turonian-Coniacian boundary (base of Abu Roash A Member) is delineated by the first appearance of the ostracod species Spinoleberis yotvataensis yotvataensis, Antepaijenborchella sp. and Cythereis rawashensis rawashensis and the calcareous nannofossils Quadrum giganteum.The boundary between the Cenomanian and Turonian (at basal part of Abu Roash EMember) ismarked by the first appearance of the foraminifera Guembelitria cenomana, Daxia cenomana and Thomasinella punica, the ostracod species Amphicytherura distincta, Veeniacythereis streblolophata and Cytherella aegyptiensis and the calcareous nannofossils species Corollithion kennedyi, Owenia hillii and Calculites cenomanicus. The recorded missing within ages is mainly due to structural elements except for the Campanian of Khoman B which is related to a local unconformity. Paleoenvironmentally, the lithological characteristics and fossil associations indicate that all members of the Abu Roash Formation and the upper part of the Bahariya Formation range from subtidal to inner shelf, except the basal part of Abu Roash E, Abu Roash F andKhoman Bmemberswere depositedwithin openmarine settings.
The Lower Mississippian Lodgepole Formation in the Williston Basin of North Dakota is a carbonate succession that reaches a maximum present-day thickness of*900 ft (275 m) near the center of the basin. Twenty cores and more than 1,450 petrophysical well logs from theWilliston Basin in North Dakota and South Dakota were used to evaluate the large-scale stratigraphic architecture of the Lodgepole Formation in the south-central part of the Williston Basin. Six sequence stratigraphic cycles and numerous sub-cycles are recognized within the Lodgepole Formation. Maximum flooding surfaces mark the boundaries between these cycles, and these surfaces are identified in petrophysical logs by having higher gamma ray API values that correspond with organic shale, fossiliferous marl, and wackestone. The intervening strata between the flooding surfaces have lower gamma ray API values that correspond with less argillaceous carbonate facies including fossiliferous wackestones and packstones. The Lodgepole cycles collectively comprise a carbonate ramp system and have laterally variable thicknesses due to their lenticular-shaped dimensions and compensational stacking patterns. The Lodgepole Ramp was constructed in three phases, an early northward progradation phase (cycles 1 and 2), a middle aggradation phase (cycle 3), and a late west-northwestward progradation phase (cycles 4–6). An unconformity surface at the top of the Lodgepole impacts the total thickness of the Lodgepole Formation in such a way that some paleoerosional patterns of the subaerially exposed Lodgepole Ramp can be observed in parts of the basin.
A high-resolution biostratigraphic analysis based on planktonic foraminifera at the Bade section (Dohuk area, northwest Iraq) across the K-Pg boundary shows an uninterrupted pelagic succession. The succession consists of the uppermost part of the bluish marlstone of the Shiranish Formation (Maastrichtian), and the buff brown shaley marlstone of the Aaliji Formation (Danian in age). The planktonic foraminiferal data reveal the occurrence of three (CF3, CF2, CF1) Cretaceous biozones for the uppermost Maastrichtian stage, and six (P0, Pa, P1a, P1b, P1c, P2) Paleogene biozones for the Danian stage. Chemostratigraphic analyses along with XRD of the primary mineralogy including the clay mineral assemblages, and field gamma-ray spectrometry fully support the interpretation of the biostratigraphic data, the identification of the K-Pg transition of the Bade section, and its link to the globally recognized meteorite impact of the Chicxulub crater (Yucatán Peninsula, Gulf of Mexico). The 4 mm-thick KPg boundary layer is a rusty-looking, yellowish red, discontinuous, and laminated, horizon. This layer is rich in impact ejecta of iron spherules, deformed quartz grains, and goethite and coesite minerals. A consistent drop of CaCO3 and the radiometric peak of the total gamma-ray radiation across the boundary zone correspond to the globally documented profiles of the K-Pg boundary zone at many global localities. These are important diagnostic features of the globally recognized meteorite impact material, with which, the Bade section is correlated to the “distal” localities of the K-Pg sections worldwide. The complete, well preserved, and unique features of the K-Pg transition at the Bade section support considering it as a reference section for the K-Pg boundary in the Arabian plate.
At the 78th Annual Meeting of the North American Commission on Stratigraphic Nomenclature, 16 October, 2023, a hybrid meeting hosted in Pittsburgh, Pennsylvania, the Commission voted unanimously to accept the revision of Articles 7 and 20 of the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 2021) as printed below. These replace all older versions of the specified Articles. An application for this revision (MacNaughton et al. 2022) was published in Stratigraphy more than one year prior to the Annual Meeting; thus, the vote on this application for revision follows Article 21 of the Code.
