Event Stratigraphy Research Articles

Chemostratigraphic characterization of the Lower Paleozoic Amdeh Formation outcrops and correlation to the subsurface Haima Supergroup and Nimr Group, Sultanate of Oman

A chemostratigraphic correlation between the siliciclastic Lower Paleozoic Amdeh Formation outcrops of the Saih Hatat area, just south of Muscat, and the hydrocarbon-bearing Haima Supergroup and Nimr Group of subsurface Oman is presented. The Amdeh Formation is a 3.4 km-thick succession of Cambrian to Ordovician-aged sandstones and shales, divided into five lithological members (Am1–Am5). The Amdeh Formation type section was sampled throughout for inorganic elemental geochemistry, quantitative mineralogy and U–Pb zircon geochronology. A robust chemostratigraphic framework for the equivalent Haima Supergroup and Nimr Group intervals, defined in the subsurface, is utilized to correlate with the Amdeh Formation. The Amdeh is interpreted to be a basinward, fully marine, time equivalent of the subsurface Haradh (and likely also the Karim), Amin, Miqrat, Al Bashair, Barik, Mabrouk, Barakat, Ghudun and Saih Nihayda formations. This correlation is based on the identification of key mineralogical, depositional, provenance and sequence stratigraphic events within the inorganic geochemical data, guided by outcrop observations of depositional facies and key surfaces, and existing biostratigraphy. Positioned beyond the northern edge of the Ghaba Salt Basin, the Amdeh Formation outcrops provide important constraints on subsurface reservoir distribution, palaeogeography and basin evolution, factors that are relevant to deep gas prospectivity.

Stable carbon isotope chemostratigraphy of the base of the Callovian in Greenland

D’Orbigny named the Callovian stage after Kellaways in Wiltshire, UK, in the 1850 s. However, agreement on its boundaries and, more recently, on the position and location of the Global Boundary Stratotype Section and Point (GSSP) for the base of the Callovian has proven difficult for the last 170 years. This is mainly due to the lack of agreement on the appropriate index fossil and its regional and global correlations, as well as the location of the stratotype section. Stable carbon isotope chemostratigraphy and event stratigraphy are now essential tools for aiding in the definition of GSSPs. In this study, stable carbon isotopic analysis of 91 samples from east Greenland’s Middle Jurassic shallow marine sandstones of the Pelion Formation (Store Koldewey and Hold with Hope) and correlative and well-dated offshore siltstones and mudstones of the Fossilbjerget Formation (Jameson Land) is used to discriminate several isotopic events previously observed in other European basins and propose the early Callovian (δ13CTOC) positive carbon isotopic excursion as a secondary marker for defining the Callovian GSSP. The early Callovian (δ13CTOC) positive carbon isotopic excursion is a fundamental tool for superregional correlation between candidate GSSPs and Standard Auxiliary Boundary Stratotypes. It can also help establish a chronological order (synchronous vs diachronous) of species occurrences between different locations.

Japan Trench event stratigraphy: First results from IODP giant piston coring in a deep-sea trench to advance subduction zone paleoseismology

The International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology, represents the first utilization of giant piston coring (GPC) within scientific ocean research drilling. This allowed for a Mission Specific Platform (MSP) multi-site, multi-hole, shallow subsurface coring in an ultra-deep water subduction zone trench. The primary objective of the expedition was to investigate the concept of submarine paleoseismology in the Japan Trench, which involves studying long-term records of deposits in the deep sea that can provide insights into past earthquake events. In this paper, we compile and interpret initial shipboard data and results to (1) establish first-order event stratigraphic correlation of thick event beds (> 50 cm in thickness) between sites, (2) test previously published event-stratigraphic predictions of earthquake-related event deposits as proposed based on high-resolution hydro-acoustic subbottom profiler (SBP) data, and (3) derive SBP-scale event deposits age estimates to (4) discuss the advantages and limitations of giant piston coring for scientific drilling operations and the potential of new event stratigraphy results for advancing submarine paleoseismology.The findings of the study identified a total of 77 SBP-scale event beds across 15 sites along a trench-parallel transect spanning over 600 km. These event beds exhibit clear expressions in SBP data, with approximately 49 % matching precisely with SBP units previously identified by Kioka et al. (2019a). For the remaining 51 % of SBP-scale event beds, thin, acoustically-transparent bodies were observed between high-amplitude horizons, for which SBP-based seismic interpretation alone would not be definitive. Consequently, the study concluded that the SBP-scale event-stratigraphy observed in IODP 386 cores validates the event-bed mapping conducted by Kioka et al. (2019a) and improves SBP interpretation for event beds in the 0.5 to 1 m thickness range.The initial age constraints obtained from shipboard radiolarian biostratigraphy enable us to provide rough estimates of event ages by linearly interpolating between previously dated events occurring less than 2000 years ago and a datum around 11,000 years ago reported in four boreholes from trench basins in the Southern, Central, and Northern Japan Trench. Inter-site stratigraphic correlation reveals distinct SBP-scale event stratigraphies for the trench segments located to the north and south of the structurally complex “boundary area” at approximately 39.3–39.4°N, which is hypothesized to potentially act as a persistent rupture barrier for megathrust earthquakes. We observe more frequent but thinner event deposits in the Southern and Central Japan Trench, and fewer but thicker event beds in the Northern Japan Trench. This spatial variation may be related to the different seismogenic behavior of the various asperities along the Japan Trench megathrust and/or to differences in the response of slope sediments to earthquake shaking. However, here-presented investigations at the SBP-scale level are deemed too simplistic for robust application of the “submarine paleoseismology” approach. The extensive and high-quality dataset from IODP GPC, coupled with the encouraging initial correlation results presented here, leads us to hypothesize that further detailed studies can identify and characterize event deposition dynamics at the micro-facies level, refine sediment provenance, and constrain precise event ages necessary for evaluating synchronicity in paleoseismological interpretation. These studies will also enable robust exploration of along-strike correlations or variations, facilitating the extraction of paleo-earthquake signals from Japan Trench event stratigraphies.

Late Pleistocene to Holocene event stratigraphy of Lake Hallstatt (Salzkammergut, Austria): revealed by the Hipercorig drilling system and borehole logging

Abstract. The Hipercorig Hallstatt History (H3) project aims to unravel the entire Late Glacial to Holocene sedimentary succession recording past climate, environment, natural hazard impacts, human–environment interactions, and prehistoric mining history. We successfully cored 51 m of the sedimentary succession of Lake Hallstatt, revealing a high-resolution Late Pleistocene to Holocene sediment record, overcoming the previous coring limit of 15.63 m (dated to ∼ 2.3 ka cal BP). The novel drilling platform Hipercorig allows the recovery of undisturbed long cores and the acquisition of borehole logging data of deep lakes. The sedimentary record is spliced to a composite core profile, and for the first time borehole logging data are linked to a core–log seismic correlation of an intra-mountainous lake of the Eastern Alps. The recovered sequence consists of two major lithostratigraphic units: (i) Unit 1 (Holocene, 0–41.7 m below lake floor) with 10 (up to 5.1 m thick) instantaneous deposits and (ii) Unit 2 (Late Pleistocene, > 41.7 m below lake floor). The Late Pleistocene sediments comprise the Younger Dryas and the deepest recovered sediments likely date back to the Allerød interstadial. Within the Holocene, six different periods are observed in the core and borehole logging data, showing distinct physical property fluctuations and an overall increase in sedimentation rate upcore. Lake Hallstatt provides a unique prehistoric archive, being located within the UNESCO World Heritage area Hallstatt–Dachstein/Salzkammergut, a region with a rich history of human salt mining dating back to 3400 cal BP (Middle/Late Bronze Age) and one of the oldest documented cultural landscapes worldwide.

Re-evaluation of the Mesozoic–Cenozoic biostratigraphy of the Laurentian Subbasin of the Scotian Basin, offshore eastern Canada

We use new and existing nannofossil, palynological, and microfossil biostratigraphic data in conjunction with lithologic and geophysical logs from four wells to establish a series of sequence-stratigraphic events in the Mesozoic–Cenozoic of the Laurentian Subbasin of offshore Newfoundland, eastern Canada. Well biostratigraphic events are integrated with reflection seismic in the area to correlate regional seismic stratigraphic surfaces. The four wells are: Bandol-1, Emerillon C-56, East Wolverine G-37, and Heron H-73. We extend the event stratigraphic scheme previously developed for the Scotian Margin, offshore Nova Scotia, into new areas to the east along the southern Grand Banks, where we recognize four new well-log sequence stratigraphic events, and we modify the definition of a previously recognized regional surface. The new and modified regional surfaces are the Early Albian Unconformity, the Late Bathonian Maximum Flooding Surface (MFS), the Late Bajocian MFS (renamed from Bathonian/Bajocian MFS), the ?Bajocian/Toarcian Unconformity, and the Late Pliensbachian MFS. We recognize the "Avalon Unconformity" and "Base-Tertiary Unconformity" of previous studies as amalgamations of multiple smaller-scale unconformities and refine their age in the studied wells. A major improvement over our earlier Scotian Margin event schemes is the extension of the event stratigraphy into the Early Jurassic using a suite of marine biostratigraphic markers. We compare the Early Jurassic event scheme to Deep Sea Drilling Project Site 547B on the conjugate Moroccan Margin to better constrain potential source rock intervals and the early history of the central Atlantic Ocean.

Main Ordovician–Silurian events in the South Ural and event stratigraphy regional tasks

The main regional abiotic events of the Ordovician and Silurian of the Southern Urals are manifested in the restructuring of sedimentation in the paleobasin. Eustatic fluctuations and tectonic motions primarily cause changes in the lithological composition of strata. Geochemical events influence the isotopic composition of elements.
 Biotic events affect biodiversity in micro- and macrofauna complexes. The largest of the five Phanerozoic extinctions was the global extinction event at the Ordovician–Silurian boundary (LOME). The Ordovician biotic diversification event (GOBE) is divided into three phases. The Darrivillian level of manifestation of this event is noted in the Southern Urals.
 The location of the global biotic events GOBE, LOME, and the geochemical event HICE in the sections of the Southern Urals is substantiated. Based on the analysis of the connection between biotic and abiotic events in the Ordovician-Silurian deposits of the Southern Urals, the significant role of conodonts, graptolites, chitinosoans and their correlation potential were revealed. Insufficient knowledge of the sections makes it possible to correlate regional events with certain assumptions.
 In order to carry out global event correlations, in addition to the comprehensive biostratigraphic characteristics of the Ordovician and Silurian deposits of the Southern Urals, geochemical studies of a number of sections are necessary. The most promising sections for identifying event levels are the sections of the western slope of the Zilair synclinorium: Nabiullino, Maksyutovo, Gremyachiy, Kaga-V.Avzyan, Sermenevo.

Late Silurian event stratigraphy and facies of South Wales and the Welsh Borderland, United Kingdom

AbstractLithofacies and biostratigraphical analysis has enabled the establishment of a stratigraphic event framework for Ludfordian and Pridoli strata in south Wales and the Welsh Borderland. In SW Wales, the Golden Grove Axis acted as a structural hinge separating the shallow marine storm-influenced Cae’r mynach Seaway from a pediment surface above which Ludfordian colluvium (Abercyfor Formation) was deposited. The Axis seeded four NW-derived river-influenced delta progrades of Leintwardinian to early Pridoli age (Tilestones Formation). A NE-sourced early Pridoli wave-influenced delta deposited the Downton Castle Sandstone Formation (DCSF), coeval to the youngest Tilestones prograde, with a lateral interface existing between Mynydd Epynt and the Clun Forest area. Except for the Malverns area, the DCSF is no longer recognized south of the Neath Disturbance. Early Pridoli forced regression promoted widespread subaerial exposure north of the Neath Disturbance, with incision into tracts close to the Welsh Borderland Fault System. The basinward-shift in facies belts resulted in marine erosion and deposition of a phosphatic ravinement pebble lag. The wave-influenced Clifford’s Mesne Sandstone Formation delta subsequently seeded on the Gorsley Axis with tidally influenced Rushall Formation accumulating in a back-barrier setting. The Pwll-Mawr Formation records the easterly advance of coeval coastal deposits on the western side of the remnant Cae’r mynach Seaway. Behind migrating delta coastlines, green muds accumulated on coastal plains (Temeside Mudstone Formation) with better drained red dryland alluvium (Moor Cliffs Formation) charting expansion of Old Red Sandstone lithofacies. Mid-Pridoli incision preserves the Pont ar Llechau Formation estuarine valley fill.

Optimized event stratigraphy of Cenomanian-Turonian ostracods of North Africa and the Middle East

During the Cenomanian and Turonian, high eustatic sea levels combined with subsidence of North Africa resulted in widespread marine inundation and the evolution of an indigenous benthic fauna, including many endemic ostracod taxa. This is the first study to combine all information on the ranges of Cenomanian and Turonian ostracods and associated planktonic foraminifera across North Africa and the Middle East into a single event-stratigraphic composite scale. Information includes the ranges of the taxa in measured sections and wells in published articles and in unpublished theses and dissertations. Nine events are tracked across the region and are used to subdivide sections and wells into subsections whose boundaries separate older sections below from younger sections above. Pseudosections were coded to represent the older and younger surfaces of the events that are separated by a very thin interval. The subsections provide a geologic framework of ordered packages of sections and associated biologic events. In this methodology, the sequence stratigraphy is an integral part of the biostratigraphic analysis. This study includes 121 sections and wells that were subdivided into 218 sections and subsections, including the nine pseudosections, the first and last occurrences of 189 taxa, and 18 unpaired events, which resulted in a total of 396 events. This information was coded into software that uses a heuristic algorithm to optimize the sequence of events. The resulting composite was used to correlate the sections and subsections, produce range charts, and calculate diversity of ostracods. Computer runs were made for each of the four study areas (Morocco and western Algeria, eastern Algeria and Tunisia, Egypt, and the Southern Levant) separately and unitedly. Run separately, diversity peaks reflect biases of the local available information, but the combined results show steady rates of evolution and extinction that produced a peak in diversity of 66 species in the late Cenomanian. There are no mass extinction events. The continued faunal turnover also indicates that there is no community stasis in the Cenomanian-Turonian ostracods of the region.

Biased, Spasmodic, and Ridiculously Incomplete: Sequence Stratigraphy and the Emergence of a New Approach to Stratigraphic Complexity in Paleobiology, 1973-1995.

This paper examines the emergence of a new approach to stratigraphic complexity, first in geology and then, following its creative appropriation, in paleobiology. The approach was associated with a set of models that together transformed stratigraphic geology in the decades following 1970. These included the influential models of depositional sequences developed by Peter Vail and others at Exxon. Transposed into paleobiology, they gave researchers new resources for studying the incompleteness of the fossil record and for removing biases imposed by the processes of sedimentary accumulation. In addition, they helped reconfigure the cultural landscape of paleobiology, consolidating a growing emphasis on fieldwork and eroding the barrier that had been erected in the 1970s between "paleontology" and "paleobiology." This paper traces these developments, paying special attention to the simulation models of stratigraphic paleobiologist Steven Holland. It also considers how the integration of sequence and event stratigraphy and paleobiology has begun to influence long-running discussions of incompleteness and bias in the fossil record.

Lacustrine evidence reveals spatially and temporally distinct Holocene ruptures on the Sawtooth Fault, Central Idaho, USA

ABSTRACTThe Sawtooth Fault in central Idaho, USA, is a range‐bounding normal fault with a Late Pleistocene–Holocene scarp near the up‐valley ends of several range‐front lakes. Cores from Redfish Lake, which spans the fault, exhibit evidence of catastrophic sediment re‐mobilization in two sequences consisting variably of intraclastic mud‐clast conglomerate, massive homogenite, and graded silt and clay. Event strata of the younger sequence are in unconformable contact with Pleistocene sediments in two cores on the northern lake‐basin slope, suggesting transport from the down‐valley portion of the lake toward the basin center. A silt cap associated with the event strata is preserved at all coring sites. The event sequence, distributed lake‐wide, dates to ca. 4300 cal a bp, while additional event strata in two Redfish Lake cores pre‐date the 7627 cal a bp Mazama ash. We propose seismic triggering of the sediment disruptions. Asynchronous event stratigraphy in Pettit Lake, 15 km south of Redfish Lake, suggests distinct ruptures along two portions of the Sawtooth Fault. The sedimentology and geochemistry of remobilized sediments in both lakes indicates that sources included Late Pleistocene and early Holocene lake‐floor sediments and suggests failures that cut deeply into the sedimentary sequence. Cores collected from Stanley Lake (17 km northwest of Redfish Lake) following the nearby 2020 M6.5 Stanley earthquake exhibit a thin, sandy event horizon associated with documented delta collapse. Subaerial slope failures associated with the 2020 event left no widespread disturbance stratigraphy in Redfish Lake. We conclude that the large‐magnitude lake‐floor sediment remobilization events probably required rupture of fault sections proximal to Redfish and Pettit lakes.

Large earthquakes along slow converging plate margins: Calabrian Arc paleoseismicity based on the submarine turbidite record

The Calabrian Arc subduction-rollback system hosts seismogenic faults capable of generating earthquakes exceeding magnitude 7. Since earthquakes are the result of long-term geodynamic processes, documenting seismic activity during a sufficiently long time interval is of fundamental importance for hazard scenarios. Instrumental and historical data provide critical information on seismogenesis, but they cover time periods shorter than the recurrence times of large earthquakes, especially in areas with low deformation rates such as Calabria. If onshore paleoseismological studies are fundamental to compile earthquake catalogs, they are sometime affected by the relatively poor continuity of sedimentation in the subaerial environment.In this study we applied the paleoseismological approach to the submarine environment to reconstruct the record of high-energy sedimentary events triggered by seismic activity. We analyzed three gravity cores collected in disconnected sedimentary basins to reconstruct resedimentation processes during the Holocene, integrating inland information for a better assessment of tectonic activity and seismogenesis. Multiproxy analyses of the sedimentary record constrained by radiometric dating allowed reconstructing event stratigraphy and linking resedimented deposits to specific earthquakes.Onshore and offshore data allow to identify large-magnitude earthquakes in the central Calabrian Arc subduction system during the Holocene, with inferred epicenters located either along normal faults onshore and/or related to the slab dynamics. The turbidite record reveals 20 major events during the last 10 ka, with sources including crustal faults in Calabria (i.e. Lakes, Rossano and Cittanova faults). Analyses of sediment samples and high-resolution seismic reflection images allowed identification of different types of resedimented deposits during the last 30–50 ka. The basin-wide occurrence of three megaturbidites/homogenites suggests they are related to megatsunamis sourced by far field earthquakes along the Hellenic Arc. Megaturbidites with a more limited spatial extent are interpreted as subduction-type events in the Calabrian Arc, while thinner seismo-turbidites record the activity of crustal structures including faults onshore. Results suggest a recurrence time of 2–3 ka for major Calabrian Arc events that needs to be considered for a reliable hazard assessment in the Mediterranean region.

Physical and geochemical reconstruction of a 2.35–2.1 Ga volcanic arc (Toumodi Greenstone Belt, Ivory Coast, West Africa)

This study reconstructs the evolution of one of the oldest Paleoproterozoic arcs, which formed shortly after a period of momentous change when the Earth transitioned out of the Archean. We present new stratigraphic, geochemical and geochronological data of the Toumodi Greenstone Belt (Ivory Coast, West Africa) integrated with local and regional data to better constrain its construction and evolution. The belt consists of four main stratigraphic events: [1] A ca. 2345 Ma tholeiitic sequence formed on the sea floor far from any landmass. This juvenile crust is the oldest Birimian supracrustal sequence known and represents either a dismembered oceanic plateau or ridge basalt; [2] Nascent arc formation (ca. 2220–2160 Ma) developed initially in a subaqueous environment and transitions into emergent volcanic centres. Near Toumodi, most deposits consist of volcaniclastic debris emplaced in subaerial to shallow-water environments, but also include minor pyroclastic vent-proximal deposits. Magmas for this event are mainly basaltic andesite to andesite and are enriched in LILE and have negative Nb, Ta and Ti signatures, all of which are consistent with water-fluxed melting typical of arc magmatism. Inherited zircons and mafic xenocrysts/xenoliths together reflect the older history and nature of underlying mid- to lower-crustal rocks, [3] An intra-arc rifting-event marked by a unconformity between events 2 and 4 the correlation with pillowed tholeiitic basalts; and [4] Construction of a mature arc (ca. 2150–2100 Ma) that consists of emergent dacitic volcanic centres and more distal volcaniclastic sediments, and overlain by post-magmatic sedimentation and red-bed formation (ca. 2100–2050 Ma). Magmas for this time period are dominantly dacitic and also display geochemical characteristics of arc magmatism, but also contain high-K, indicative of melting in a thickened volcanic arc.

New geochronological results from late Mesoproterozoic to early Neoproterozoic successions in the eastern North China Craton and implications for the reconstruction of Rodinia

Late Stenian to Tonian stratum of the Xihe and Jinxian groups, the Sangwon system, the Penglai Group, the Tumen Group, and the Huaibei and Langan groups located at the eastern margin of the North China Craton provide an excellent record of changes in sediment provenance related to the amalgamation and dispersal of Rodinia and therefore the paleogeographic position of the craton. To decipher their protosource changes over time, we evaluated 7510 U-Pb and 963 Lu-Hf analyses from 92 samples across the entire eastern North China Craton, of which 1746 U-Pb and 415 Lu-Hf analyses from 18 samples are newly reported here. The detrital zircon results indicate two stratigraphic intervals with internally consistent lithostratigraphy, event stratigraphy, biostratigraphy, depositional age, and detrital zircon age patterns: the late Stenian to early Tonian strata and the late Tonian strata, of which the former mainly consists of the Mesoproterozoic detrital zircons with juvenile Hf isotopic features and the latter’s detritus chiefly derived from the Neoarchean to late Paleoproterozoic basement of the North China Craton. In consideration of the paleomagnetic and geochronological data from the coeval strata in other cratons, the Mesoproterozoic detrital zircons of the late Stenian to early Tonian strata are interpreted to be derived from the Musgrave Province in central Australia during the Rodinia amalgamation, and the transition to the autochthonic protosources in the late Tonian possibly indicated the breakup of the North China Craton and North Australian Craton connection.

Early to Mid-Holocene Tree Immigration and Spread in the Isle of Man: The Roles of Climate and Other Factors

The Isle of Man is a large island which lies in the middle of the northern Irish Sea between Britain and Ireland and, because of its insularity and size, has an impoverished flora compared with the two main islands. This has been the case throughout the postglacial and warrants the island’s description as a separate phytogeographic province. We have considered Holocene tree pollen data from seventeen sites on the island which together preserve a vegetation history that spans the six thousand years of the early and mid-postglacial from the end of the Lateglacial at 11,700 cal. BP to the mid-Holocene Ulmus decline at ca. 5800 cal. BP. Radiocarbon dating of the rational limits of the pollen curves for the main tree taxa has allowed an appraisal of the timing of each one’s expansion to become a significant component of the island’s woodland, and comparison with the dates of their expansion on the adjacent regions of Britain and Ireland. The radiocarbon dates show that, although some variability exists probably due to local factors, there is considerable concordance between the timings of major pollen zone boundaries in Britain and Ireland around the northern Irish Sea. On the Isle of Man the expansions of both Juniperus and Betula were delayed by several centuries compared to the British/Irish data, however the timing of the expansions of Corylus, Ulmus, Quercus, Pinus and Alnus on the Isle of Man all appear closely comparable to the ages for these pollen stratigraphic events in north Wales, northwest England, southwest Scotland and eastern Ireland, as are those for the Ulmus decline. It is likely that local pedological and edaphic factors on the island account for the differences in the first Holocene millennium, while regional climatic factors governed the timings for the rest of the expansions of tree taxa across the wider region, including the Isle of Man. Disturbance, including by human agency, was important at the site scale and perhaps triggered early tree expansion in some places, including Quercus, Ulmus and Alnus. Insularity seems not to have been a significant factor in the expansion of the major forest trees.

The East Gotland Basin (Baltic Sea) as a candidate Global boundary Stratotype Section and Point for the Anthropocene series

The short sediment core EMB201/7-4 retrieved from the East Gotland Basin, central Baltic Sea, is explored here as a candidate to host the stratigraphical basis for the Anthropocene series and its equivalent Anthropocene epoch, still to be formalized in the Geological Time Scale. The core has been accurately dated back to 1840 CE using a well-established event stratigraphy approach. A pronounced and significant change occurs at 26.5 cm (dated 1956 ± 4 CE) for a range of geochemical markers including 239+240Pu, 241Am, fly-ash particles, DDT (organochlorine insecticide), total organic carbon, and bulk organic carbon stable isotopes. This stratigraphic level, which corresponds to a change in both lithology and sediment colour related to early anthropogenic-triggered eutrophication of the central Baltic Sea, is proposed as a Global boundary Stratotype Section and Point for the Anthropocene series.

Carbon isotopes, palynology and stratigraphy of the Santonian–Campanian boundary: The GSSP auxiliary sections, Seaford Head (England) and Bocieniec (Poland), and correlation between the Boreal and Tethyan realms

The stratigraphy and palynology of the upper Santonian–lower Campanian (Uintacrinus socialis–Gonioteuthis quadrata zones) Newhaven Chalk are described for the Campanian auxiliary GSSP section at Seaford Head, England. A new high-resolution bulk-sediment carbonate carbon stable-isotope (δ13Ccarb) curve provides the basis to refine the carbon-isotope event (CIE) stratigraphy of the section. Results are compared to a complementary palynological study of a second Campanian auxiliary GSSP section (U. socialis–O. pilula zones) at Bocieniec, Poland. Palynological assemblages are dominated by organic-walled dinoflagellate cysts (dinocysts; 208 taxa) at both sites. A stratigraphic framework is established via review of published lithostratigraphic, macrofossil, foraminifera and calcareous nannofossil records from the study sites. Carbon isotope curves with 13 major named CIEs provide a basis for correlation of Seaford Head and Bocieniec to sections at: Trunch, England; Poigny, France; Lägerdorf, Germany; and the Campanian GSSP at Gubbio, Italy. Correlations are constrained by biostratigraphic records, including dinocyst events. The Late Santonian δ13C Event (LSE, previously termed the Santonian–Campanian Boundary Event, SCBE) provides a key correlation level between Boreal and Tethyan sections and enables the placement of base Campanian markers: extinction levels of the crinoid Marsupites and the planktonic foraminifera Dicarinella asymetrica; the first appearance of the calcareous nannofossil Aspidolithus parcus parcus; and the C34n/C33r magnetozone boundary (the primary Campanian marker), in both Boreal and Tethyan sections. A holostratigraphy for the Santonian–Campanian boundary interval that integrates CIEs, macrofossils, benthic and planktonic foraminifera, calcareous nannofossils, dinocysts and magnetostratigraphy is presented. Rhynchodiniopsis juneae sp. nov. is described.

The proposed Anthropocene Epoch/Series is underpinned by an extensive array of mid‐20th century stratigraphic event signals

ABSTRACTThe extensive array of mid‐20th century stratigraphic event signals associated with the ‘Great Acceleration’ enables precise and unambiguous recognition of the Anthropocene as an epoch/series within the Geological Time Scale. A mid‐20th century inception is consistent with Earth System science analysis in which the Anthropocene term and concept arose, and would reflect the reality that our planet has sharply exited the range of natural variability characterizing the Holocene Epoch/Series, which the Anthropocene would therefore terminate. An alternative, recently proposed ‘geological event’ approach to the Anthropocene is primarily an interdisciplinary concept, encompassing historical and socio‐cultural processes and their global environmental impacts over a diachronous timeframe that extends back at least many millennia. Resembling more closely a geological episode than an event, it would decouple the Anthropocene from its chronostratigraphic delineation and association with an abrupt planetary perturbation; but separately defined and differently named it might be usefully complementary. We recommend a clear separation of epochs, events and episodes. An epoch is a formal subdivision of the Geological Time Scale, and its correlation may be assisted by one or more events; an event is usually, and particularly in the Quaternary, a brief incident or perturbation with a sedimentary expression; and an episode is a longer, internally complex time interval that may include several events and even extend across several epochs.

Discovery of Upper Devonian conodonts and event stratigraphy from the Eastern Jebilet, Morocco

The Abichat section in the Eastern Jebilet, including allochthonous siltstones and sandy limestones rocks, revealed the presence of a Givetian and Early Frasnian conodont fauna. The Upper Devonian is discovered for the first time in Eastern Jebilet. A continuous biostratigraphic record could not be established, because of the gap that occurs in the Upper Givetian. However, six conodont Zones are recognized: rhenanus/varcus and ansatus to semialternans of Middle Givetian, Lower-Middle falsiovalis (MN1-2), Upper falsiovalis (MN3) and transitans (MN4) of Lower Frasnian. Notably, the conodont fauna contains particularly several species of Ancyrodella, Mesotaxis and Icriodus. Givetian conodonts show a polygnathid biofacies and Lower Frasnian conodonts reveal a mixed conodont biofacies with the Ancyrodella as dominating genus. Two anoxic global events are recognized for the first time in the Massif of Jebilet, the Upper Frasnes Event and the Timan Event. The Eastern Jebilet Devonian nappes have close links with the nappes of Azrou and Mrirt-Ziyar whose the sediments, characterized by stratigraphic gaps, were deposited along the disintegrated northern continental margin of Gondwana.

Stratigraphic palynology and micropaleontological study of the Cretaceous-Paleogene succession of the Nani-1 well of the Anambra and Niger Delta basins: Implications for hydrocarbon exploration

Integrated palynological and micropaleontological analyses were carried out on the Nani-1 well drilled into the Anambra and Niger Delta basins of Nigeria. The study is aimed at reconstructing biozones and paleoenvironments of deposition, as well as deducing the sequence stratigraphic framework of the Cretaceous-Paleogene successions of an area containing key elements for hydrocarbon exploration. Encountered lithofacies succession of sandstone, siltstone, dark-grey to black shale, and coal beds comprises six lithostratigraphic units, namely the Nkporo Group (Campanian-Maastrichtian), Mamu Formation (Middle Maastrichtian), Ajali Formation (Middle-Late Maastrichtian), Nsukka Formation (Late Maastrichtian), Imo Formation (Danian-Thanetian) and Ameki Group (Eocene). Fourteen dinoflagellate zones (A-N) and seven pollen and spore subzones (A1-G1) are recognized based on the first occurrence of two or more species. Two major stratigraphic events are documented: (1) dinoflagellate cyst (dinocyst) zone G at 880 m depth marked by first appearance of Danea aff. californica and Danea cf. mutabilis in association with Cordosphaeridium fibrospinosum, and the last occurrence of Danea aff. californica and Phelodinium magnificum place the Cretaceous-Paleogene (K/Pg) boundary in the lowermost part of the Imo Formation; and (2) a hiatus characterized by a starved section observed at 380 m directly overlain by the Early Eocene assemblages of the Ameki Group indicates a sequence boundary at Imo/Ameki Boundary. Thus, a chronostratigraphic chart is developed for parts of the Anambra Basin and the Niger Delta. Six depositional environments which include marginal to shallow marine, marshy lagoon to estuarine, shallow neritic and tidally influenced fluvial channel are identified, and palynostratigraphic evidences indicate that fresh water palynomorphs are present in the Lower Maastrichtian strata. Four sequence boundaries and four maximum flooding surfaces are also identified within the Maastrichtian–Early Eocene sediments. The paleoenvironmental reconstruction shows that possible hydrocarbon reservoirs in the basin are the marine sandstone facies of the Nkporo Group and Mamu Formation. Their shale members constitute potential source rocks, while the overlying shale units of the Nsukka and Imo formations may provide regional seals for hydrocarbon habitation.

Quaternary environmental and climatic history of the northern high latitudes – recent contributions and perspectives from lake sediment records

ABSTRACTLake sediment records archive the Quaternary environmental and climatic history in northern high latitudes. Because of their spatial distribution, age range, time resolution, age control, and high sensitivity to paleoenvironmental conditions, lake records contribute to evaluating regional to hemispheric‐scale climate change. Here, we compare the characteristics of lake sediments and their qualities for paleoenvironmental and paleoclimatic reconstructions with those of other archives in northern high latitudes, and we outline the current state of research by introducing a series of regional case studies on 31 lakes as part of this special issue. The compilation shows that the coring site selection and interpretation can strongly benefit from bathymetric and seismic or hydro‐acoustic surveys. New coring techniques have become available making it possible to expand the records in length and time. Analytical work on the cores has particularly benefited from improved non‐destructive logging and scanning techniques, from the development of new proxies, and from advancements in quantitative climate reconstructions. Progress was also made in further developments of dating techniques; however, the recognition of additional isochronal events, e.g., via tephrochronology or paleomagnetic event stratigraphy, is needed to derive a better understanding of leads and lags in climate signal propagation throughout the northern high latitudes.