The earliest Fusulinida are used to assess the widely accepted hypothesis that Pseudoendothyra arose from Eostaffella, that Eostaffella arose from Eoparastaffella, and that Eoparastaffella was derived from Eoparastaffellina. The possible relationship between these taxa are examined using material from northern England. Transitional forms between Eoparastaffella and Pseudoendothyra are observed, with similar shape, profile, and wall structure, but with dis-cernible differences in the coiling of the inner whorls, as well as a clear age overlap between these genera, which suggests a direct evolution between them. The origin of Eostaffella is not sufficiently well established and could be derived either from Eoparastaffella (as many authors have proposed) or from the dainellid Paralysella. Thus, it cannot be ruled out that the order Fusulinida might be polyphyletic. The genus Eoparastaffellina is considered a valid genus and indepen-dent from Eoparastaffella with their inclusion in the differ-ent orders of Endothyrida and Fusulinida, respectively.

Neogene lacustrine and fluvial successions in the Fazzan Basin of the Libyan Sahara, provide evidence for past Saharan humid intervals, although, their extent and the nature of lacustrine marginal deposits are disputed and poorly understood. Sections at Bir al Hasy provide a basin-margin succession in the northern Fazzan Basin, where their age, relationship to basement palaeotopography and likely hydrological and environmental conditions are investigated. Two intervals of widely differing ages were discovered. The older interval from the Kunayr Member and Brak Formation is dated using a biostratigraphically-constrained magnetostratigraphy correlated to the polarity timescale and was deposited between 11.1 and 9 Ma. The upper part of the younger interval (the Bir al Hasy Member) is dated using optically stimulated luminescence at 9.8 ± 1.3 ka, suggesting it is coeval with the African Humid Period, widely identified in the Sahara. At Bir al Hasy, limestones of the Kunayr Member formed as lake margin and paludal tufa's constrained by a valley system in the palaeotopography. Stable carbon and oxygen isotope data, show that the Kunayr and Brak carbonates, were partly formed from groundwaters emanating from the adjacent Qarqaf High. Our regional environmental model for the Kunayr Member and Brak Formation suggests a lacustrine low gradient, low energy carbonate ramp deposit, formed during the Langhian to early Tortonian (Middle- Late Miocene). These palustrine carbonates are synchronised to North African hot and wet climatic events and palaeoclimatic change linked to sea-level changes in the Neo-Sirte Gulf to the east. From 13.6 Ma progressive aridity strongly impacted Lake Megafazzan.

Developing environmental and chronological data for the Miocene and Pliocene successions of the central Sahara provide a basis for refining the pacing of green Sahara episodes to consolidate debate about early hominin dispersal from eastern Africa. Sedimentological, isotopic and geomagnetic polarity datasets are used to assess the environment and age of the Zarzur Formation in eastern Fezzan, Libya. A magnetostratigraphy based on four sections, combined with a statistical comparison to the geomagnetic polarity timescale, indicate that the formation was deposited from 7.8 Ma to 4.3 Ma. Lacustrine facies comprise laminated, peloidal mud-grade carbonates (with localised gypsum) formed in varying fresh to hypersaline inter-dune lakes. A second lacustrine facies comprises gastropod-and ostracod-bearing calcareous sandstones, formed in lakes developed on sandy substrates. These systems evolved from earlier fluvial and sandy-playa environments developed in the latest Tortonian. Based on delta 13C and delta 18O from carbonates formed in the lacustrine systems and calcrete-related cements, water sources for the lake deposits varied between low to high salinity and were largely from westerly moisture sources likely from extreme precipitation events. Groundwater was an important source for the inter-dune lakes because of irregularity in precipitation. The timing of lacustrine carbonate formation was in part paced to deep lakes that developed in the East African Rift in the early Pliocene, although sandy substrate lakes also formed during the Messinian. Greening of the Libyan Fezzan during deposition of the Zarzur Formation promoted potential habitat pathways for early hominid dispersal from the Megalake Chad Basin.

The largely ice-free world of the 'Chadian'-Arundian (early Visean) is investigated in two successions in south Cumbria to better understand the relationships between transgression, hiatus and the position of the basal Arundian. A detailed foraminiferal biostratigraphy is used to age-constrain the transition from the late 'Chadian' to early Arundian. This demonstrates a good synchronous relationship between the sequence stratigraphy of the two successions and the first occurrence of key species (mostly primitive archaediscids, rapidly followed by more evolved forms of the same family), suggesting that there is no significant hiatus and that the record of faunal changes is closely comparable in the key successions. A synthesis of other 'Chadian'-Arundian boundary successions in Britain and Ireland indicates some key problems with the current Arundian boundary stratotype in practical usage. We propose a stratigraphically higher position for the Arundian boundary in the stratotype, which is more easily correlated to the Bobrikian and Moliniacian substages of eastern Europe and Belgium, respectively, and tied to the first occurrences of foraminifera species, allowing more robust age assessments, free from the confounding factors of inferred lithological or sequence stratigraphic changes.

The late Permian to Triassic (~ 260-201 Ma) is one of the hottest periods in the last 500 Ma, witnessing dramatic changes in the environment on the Pangea supercontinent, extensive low mid latitude dusty desert formation and the development of a strong monsoonal regime (Ruffell & Hounslow 2006). However, one aspect of Permo-Triassic climate that is relatively unexplored is the extent to which orbital forcing drove terrestrial environmental change in the monsoon and desert areas. The terrestrial mudstone deposits of the Aylesbeare and Mercia Mudstone groups formed under a dusty desert environment crop out along the southwest coast of England (Hounslow and Gallois, 2023) and potentially provide a means to address this gap.Here we apply dual frequency magnetic susceptibility and analysis of its frequency dependence on mudstones of the Aylesbeare and Mercia Mudstone groups in order to constrain the environmental controls on these parameters and reconstruct Permo-Triassic environmental changes. We sample for these parameters at closely spaced regular intervals and use the new magnetostratigraphic timescale of Hounslow and Gallois (2023) to ascertain variations in these parameters with both age and depth. Both bulk magnetic susceptibility at low frequency (976 Hz) and frequency dependence show considerable variation, which correspond to stratigraphic alternations between green-grey silty mudstones and red mudstones, potentially reflecting wider scale changes in water table level and humidity. Evidence from temperature‐dependent magnetic susceptibility experiments suggested prevailing of magnetite in all types of sequences with hematite evidence in a red mudstone. We propose a model where changes in a dissolution of iron oxides due to climatically driven water table level changes explains these variations in the mudstones. Spectral and wavelet analysis reveals clear orbital periodicities in the proxy data, implying orbital control on water table in these desert environments, potentially via distal monsoon precipitation. Notably, there are substantial changes in the importance of key orbital parameters in the data through time, implying strong sensitivity of this hyper-arid climate to external boundary conditions. ReferencesRuffell, A. & Hounslow, M., 2006: In P. F. Rawson, & P. Brenchley (Eds.), The Geology of England & Wales. Geological Society of London; 295-325.Hounslow, M. & Gallois, R., 2023: Magnetostratigraphy of the Mercia Mudstone Group (Devon, UK): implications for regional relationships and chronostratigraphy in the Middle to Late Triassic of Western Europe. Journal of the Geological Society 180, jgs2022-173.

Magnetostratigraphy, palynology and ammonite biochronology of the Staithes S-20 core are used in an integrated evaluation of the late Norian to early Hettangian successions in Britain. The polarity patterns of the Blue Anchor and Westbury formations differ from their counterparts in SW England, indicating younger and older ages, respectively, for those units in NE England. Magnetostratigraphy indicates an underlying Sevatian age hiatus coeval with the D5 disconformity of the German Keuper. The miospore succession from S-20 is divisible into zones like those from the St Audrie's Bay section in SW England. Using magnetic susceptibility datasets for the earliest Hettangian chronozones from S-20, Lavernock, St Audrie's Bay and Lyme Regis, a new method is used to derive a TimeOpt-based astrochronology for the earliest Hettangian. This is anchored to radioisotopic dates from Peru correlated into British sections using carbon isotope excursions. A brief reverse magnetozone in the basal Cotham Member in the Staithes S-20 core and the astrochronological evaluation demonstrate that CAMP volcanics are coeval with the end-Triassic extinction in UK sections. An eco-plant model assessment of the miospores indicates greater proportions of eurythermic and europhyte floras, suggesting stronger seasonality in palaeoclimate was probably a key factor in the end-Triassic extinction.

Plain Language Summary Nearly synchronous global changes in geomagnetic polarity give both a detailed irregular pacing to geological time and provide a glimpse into heat transfer processes across the core—mantle boundary which drives the Earth's geodynamo. Although the Late Carboniferous is characterized by some well‐studied reversals, details of the tempo of polarity changes in the Early Carboniferous are unknown. This work addresses this by providing a detailed record of polarity changes over a ∼2 million year interval at around 334.5–332.5 million years ago‐from the Trowbarrow Quarry section in NW England. We demonstrate that these limestones likely preserve magnetization from close to their time of formation and record at least 31 polarity reversals. These observations support the idea that the Earth's dynamo was in a hyperactive reversing state similar to those sustained for tens of Myr in the Late Jurassic, parts of the Cambrian and the Late Ediacaran. It further corroborates a ∼200 Myr cyclicity in paleomagnetic field behavior since the Precambrian, potentially linked to variable core heat flow forced by mantle convection.

Abstract The documentation and understanding of variations in the Earth's magnetic field through time is fundamental for several disciplines, but current geomagnetic models rely on datasets heavily biased toward the mid‐ and high northern latitudes. The African continent and surrounding islands and oceans are particularly underrepresented. Here, we present a new record of paleo‐secular variation (PSV) of the inclinations over the last 23 ka from Lake Chala, situated at 3°S near Mt Kilimanjaro in eastern equatorial Africa. This groundwater‐fed crater lake is characterized by a high sedimentation rate (ca. 1 cm/10 years) and a particularly well‐constrained age model based on 210Pb and 14C dating. The magnetic mineralogy of the sediments is tested with rock magnetic analyses. The Lake Chala inclination record shows four highs and lows over 20 ka and compares well with that of Lake Malawi (10°S) between 20 and 16.2 ka, and from 9.8 to 2.6 ka. This record is linked to PSV records at Lakes Victoria and Malawi using a sequence slotting technique to generate a composite PSV model for east Africa. Analyzed at best‐possible resolutions up to 200 years, the Lake Chala PSV record not only represents an important contribution to improve our understanding of local and global features of the Earth's magnetic field. It also expands the utility of paleomagnetism as a key tool for dating and correlation both for archeological sites throughout East Africa and the many volcanoes, active or dormant, of the East African Rift System.

The late Asbian appears to mark the initial, well-documented, onset of far-field glacio-eustatic changes in equatorial Mississippian strata. This work unravels the nature of cyclicity in upper Asbian shallow marine carbonates, using a combination of petrographic study, rock magnetic proxies and astrochronological testing on samples from the Trowbarrow section, NW England. Rock magnetic data express the content of two types of siliciclastic sources; a marine-delivered magnetite-dominated source, and an eolian-delivered, hematite-dominated source. The eolian-sourced material generally peaked during regressive and low-stand parts of the carbonate rhythms. Astrochronologic testing methods based around the average spectral misfit and TimeOpt methodology show the magnetite abundance proxies are principally carrying the astronomically forced signal. Two likely sedimentation rate models are derived from the five better magnetic proxies using evolutive methods. In addition, a set of three likely major hiatus levels are inferred in the sedimentation rate models, based on testing possible major hiatus scenarios with TimeOpt methods, using eccentricity modulation. From these, using the three best proxies, an average astrochronologic duration for the Trowbarrow section suggests a late Asbian duration of 1976 +/- 86 kyr (1 sigma), and a basal late Asbian age of 334.48 +/- 0.35 Ma (2 sigma). Coupled atmosphere-ocean models for the late Paleozoic, suggest that lows in short eccentricity correspond to glacials, when inferred delivery of siliciclastic sediment to the carbonate ramp is generally at a maximum. The glacial and lower sea-level intervals also coincide with maximum delivery of eolian siliciclastics, likely linked to increased aridity and less vegetation cover on adjacent and distal parts of Laurentia. Around 332-333 million years ago changes in sea-level driven by changes in polar ice volume were an important control on the sedimentation patterns through time in carbonates from low paleolatitudes. Understanding the pacing of these changes has implications for timescales and paleoceanographic processes. These cyclical changes in carbonate lithology are related to changes in magnetic properties within the late Asbian (late Visean) section at Trowbarrow in NW England. The magnetic changes principally express differences in the small content of silica-based clastics, but also reflect changing Fe-oxide mineralogy between times of hematite-rich and magnetite-rich clastic input. The changes are responding to differences in eolian delivery and marine dispersal of the clastics. Eolian delivery of clastics was at its peak near sea-level lowstands, when nearby terrestrial systems were the most arid and supplying the most dust. Statistical assessments show that the magnetite abundance signal principally expresses changes in astronomical eccentricity. Primarily using the expected eccentricity pacing, two age models are constructed, which includes three levels of detectable hiatus in the section. Using these two age models and the three best magnetic proxies, the average late Asbian duration is 1976 +/- 86 kyr, with the base of the late Asbian at 334.48 +/- 0.35 Ma. Rock magnetic properties show the included siliciclastics are from hematite-rich eolian dust and marine-dispersed sources The magnetite mineral abundance proxies principally carry the primary eccentricity-driven astronomical signal An astrochronology for the late Asbian indicates its duration is 1976 +/- 86 kyr

Understanding the synchronicity of global climatic, environmental, and biotic events around the NorianRhaetian boundary (NRB) is problematic because of major international differences in biochronology. We instead use magnetostratigraphic and global carbon isotopic changes to produce more precise global correlation. This work focusses on the base and top of the Rhaetian, with principal age control from a new late Norian to latest Rhaetian magnetostratigraphy from Lavernock (southern Wales) which can be directly correlated to the proposed NRB sections at Pignola Abriola (Italy) and Steinbergkogel (Austria). A disconformity exists in the Lavernock section in its late Norian part (Branscombe Mudstone Formation), but the NRB interval is largely complete. The magnetostratigraphy and a composite delta 13 C org stratigraphy from three British sections, demonstrate synchronous changes in both terrestrial and marine records. This analysis indicates the older proposed definition of the NRB from Steinbergkogel is in the upper few metres of the Branscombe Mudstone Formation, while the younger NRB definition from Pignola Abriola is in the upper parts of the Blue Anchor Formation. The latest Rhaetian magnetostratigraphy from Lavernock records reverse magnetochrons UT26r and UT28r which closely pre-date and post-date the widely recognised Marshi and Spelae carbon isotope excursions, respectively. Magnetochrons UT28r and UT27r were previously recognised at St Audrie's Bay (SW England), with relationships to the Newark Supergroup which tightly constrain the first phase of CAMP eruptions to overlap the Spelae excursion. The carbon isotope excursions present in the Blue Anchor Formation lacustrine successions, demonstrate the likely atmospheric, and global spread of these perturbations.

Documenting the Earth’s magnetic field variations through time is fundamental for several disciplines. However, current geomagnetic models heavily rely on datasets biased towards mid- and high northern latitudes, whereas data from Africa and surrounding oceans are particularly underrepresented. In this study, we present a new record of paleo-secular variations (PSV) in geomagnetic field inclinations during the last 23 ka from Lake Chala, situated at 3° S near Mt Kilimanjaro in eastern equatorial Africa. This deep groundwater-fed crater lake is characterized by a high sedimentation rate (ca. 1 cm/10 years) and a particularly well-constrained age model based on 210Pb and 14C dating; and rock magnetic analyses have demonstrated the magnetic stability of the sediments. The Chala dataset is linked to PSV records from Lake Malawi and Lake Victoria using a sequence slotting technique to generate a composite PSV record for East Africa. The Lake Chala PSV record not only represents an important contribution toward a better understanding of local and global features of the Earth’s magnetic field, but also expands the utility of paleomagnetism as a key tool for dating of, and cross-correlation between, lake-based paleoenvironmental records and archeological sites throughout eastern tropical Africa.

Abstract First occurrences of selected foraminifers and their interpreted phylogenies in the uppermost Arundian Substage of the South Cumbria Shelf, northern England, allows the distinction of four biostratigraphic events. Event A1 is characterised by the occurrence of occluded Nodosarchaediscus, Consobrinellopsis, and Archaediscus krestovnikovi and is assigned to the ‘upper’ Cf4δ subzone. Event A2 is characterised by the first occurrence of Pojarkovella ketmenica and Archaediscus at concavus stage (including the first A. pauxillus) and is assigned to the base of the Cf5α subzone. Event A3 is characterised by Koskinotextularia aff. cribriformis, Koskinotextularia sp., Archaediscus moelleri, Endothyranopsis compressa, and Omphalotis minima and is assigned to the base of the Cf5β subzone. Event A4 is characterised by the first occurrence of Koskinotextularia cribriformis, Koskinotextularia bradyi, Koskinotextularia obliqua, and Pojarkovella nibelis morphotype 2. The base of the Cf5α subzone likely coincides with the base of the Livian in Belgium and Tulian in the Russian Platform, although the occurrence of hiatuses and facies barren in foraminifers leads to uncertainty in correlation. The Cf5β subzone is correlated with that part of the Livian and Russian Platform succession with preserved foraminifers and thus can be used for worldwide correlations. However, formally, it cannot be confirmed if this horizon is an isochronous level (due to hiatuses and hostile facies), and it is necessary to locate a slightly higher level of potential correlation that better displays the absence or presence of the successions, such as event A4.

Global synchronization of environmental change in terrestrial successions in deep time is challenging owing to the paucity of dating methods, a case also applicable to the Middle to Upper Triassic Mercia Mudstone Group in Britain. Using coastal cliff sections, magnetostratigraphy was evaluated at 263 horizons, defining 53 magnetozones. Magnetozones from the lower 140 m of the group demonstrate correspondence to those from the mid-Ladinian to early Carnian polarity timescale, dating that is compatible with magnetostratigraphy from the underlying Sherwood Sandstone Group. Magnetostratigraphy of the Dunscombe Mudstone Formation, and associated palynological data, suggest a late Carnian to earliest Norian age, and a dramatically lower accumulation rate than for adjacent formations. The polarity record demonstrates coeval flooding events, evaporite deposits and intervals of sand supply between the Wessex Basin and the Central European Basin in the Carnian. This is the result of linked climatic and eustatic changes between these separate basins, related to aeolian dust supply and the shrinkage of hyper-arid source regions for the fine material. Magnetostratigraphy from the Branscombe Mudstone and Blue Anchor formations demonstrates their Norian and early Rhaetian age. These and other data suggest an alternative synchronization of marine and non-marine polarity records for the Norian polarity timescale. Supplementary material : Section details and detailed logs of the sampled sections and inferred sequence boundaries, magnetic mineralogy data, demagnetization behaviour and mean directions, summary of virtual geomagnetic pole data and a comparison with other European poles, construction of other composite reference sections and revised polarity scales, an Excel sheet of magnetic data, statistically evaluated correlation models and age models are available at https://doi.org/10.6084/m9.figshare.c.6613788

Early diagenesis of marine organic matter dramatically impacts Earth's surface chemistry by changing the burial potential of carbon and promoting the formation of authigenic mineral phases including carbonate concretions. Marine sediment-hosted carbonate concretions tend to form as a result of microbial anaerobic diagenetic reactions that degrade organic matter and methane, some of which require an external oxidant. Thus, temporal changes in the oxidation state of Earth's oceans may impart a first-order control on concretion authigenesis mechanisms through time. Statistically significant variability in concretion carbonate carbon isotope compositions indicates changes in shallow marine sediment diagenesis associated with Earth's evolving redox landscape. This variability manifests itself as an expansion in carbon isotope composition range broadly characterized by an increase in maximum and decrease in minimum isotope values through time. Reaction transport modelling helps to constrain the potential impacts of shifting redox chemistry and highlights the importance of organic carbon delivery to the seafloor, marine sulfate concentrations, methane production and external methane influx. The first appearance of conclusively anaerobic oxidation of methane-derived concretions occurs in the Carboniferous and coincides with a Paleozoic rise in marine sulfate. The muted variability recognized in older concretions (and in particular for Precambrian concretions) likely reflects impacts of a smaller marine sulfate reservoir and perhaps elevated marine dissolved inorganic carbon concentrations. Causes of the increase in carbon isotope maximum values through time are more confounding, but may be related to isotopic equilibration of dissolved inorganic carbon with externally derived methane. Ultimately the concretion isotope record in part reflects changes in organic matter availability and marine oxidation state, highlighting connections with the subsurface biosphere and diagenesis throughout geologic time.

Foraminiferal diversity and taxa richness from beds transitional between the Asbian and Brigantian substages (Middle Mississippian) show patterns of secular change which allow detailed inter-regional correlations to be established. Foraminifera from the Askrigg Block, Stainmore Trough, Alston Block, South Cumbria Shelf and Solway Basin show similar secular changes (foraminiferal trends, FTs), allowing correlation to be made with the basal Brigantian Stratotype at Janny Wood. Despite the absence of consistent microfossil first occurrence markers for the recognition of the base of the Brigantian, this horizon can be confidently recognized by means of foraminiferal trends. The FTs allow the precise location of the base of the correlated Brigantian in sections where this boundary was questioned or controversial in previous studies, as well as to amend the position of the foraminiferal zones and subzones during the late Asbian and basal Brigantian. This type of analysis when used in combination with foraminiferal zonations, emergent surfaces and lithological cyclicity, together, provide a robust means for high-resolution correlation. This methodology, provides the least uncertainty in sections that have been most densely sampled, whereas for less intensely sampled sections there is more correlation uncertainty.

High-resolution foraminiferal biostratigraphy of carbonates immediately below and near the base of the Holkerian Substage in three sections of the South Cumbria Shelf allows the recognition of the Cf5 alpha and Cf5I3 subzones. The most complete section at Grubbins Wood is almost free of dolomitisation. At the White Scar Quarry and Barker Scar sections, minor faunal gaps are inferred at the base of one or both subzones, respectively. The Grubbins Wood section has the most limited exposure, whereas White Scar Quarry has extensive exposure of this interval, especially the basal horizons of the subzones, compared to Barker Scar. The Grubbins Wood section, because of its exceptional foraminiferal record is more suitable for the establishment of a coincident boundary stratotype for the mid Visean and Holkerian boundary at the base of the Cf5I3 subzone. However, the Barker Scar section should be retained as the Holkerian unit stratotype for Britain, with the base of the Holkerian repositioned lower in the section, at the base of the Cf5I3 subzone. White Scar is a suitable unit-parastratotype, filling data gaps due to possible faunal gaps and dolomitisation at Barker Scar. The rich foraminiferal assemblages allow good global correlation with other regional zonations, which if refined in other countries, would allow a more affirmative global chronostratigraphic basal boundary for the middle Visean.

A study of calcareous algae from the late Vise ' an to Serpukhovian interval in basins from the western margin of Palaeotethys (basins located currently in Western Europe and Northern Africa) shows varied responses in terms of palaeoecological diversity, specimen abundance, genus richness and taxonomic distinctness for the lowlatitude basins. Algal associations are more similar in cratonic areas, although many local diversity peaks correspond to ecological/environmental factors. Terranes with Laurussian affinities contain the most unusual abundances and seem to be the most affected by palaeogeographic reorganization and local tectonics. Algae from the palaeo-equatorial zone show more dramatic changes than those in the southerly tropics. The varied results suggest that it is not suitable to extrapolate a particular diversity result from a single region to global conditions, since many factors have influenced the regional assemblages.The main taxonomic turnover of most fossil groups occurred from the uppermost Serpukhovian, linked to a severe cooling phase inferred by delta 18O data from brachiopods. It coincides with the post-glacial phase C1 defined in eastern Australian basins. Most ecological changes occurred from the early Serpukhovian, predating the glacial phase C1 and coinciding with the Main Eustatic Signal. Far-field proxies used to define the onset of icehouse intervals in the LPIA are inconsistent and are located several million years before the main biota changes. This questions the definition of the onset of sustained icehouse glaciation at different levels of the low palaeolatitude Vise ' an, without the resulting modifications in the warm-water biota.

SUMMARY Prior work on rotational remanent magnetization (RRM) and rotational anhysteretic remanent magnetization (ARMROT) has demonstrated promise for magnetic mineral identification in earth materials. One challenge has been to calibrate the measurements to magnetic mineral types and microstructural controls, since previous studies have used differing spin rates, alternating field (AF) intensities and decay times, which hinders a comparison of data sets. Using a RAPID magnetometer we show that the range of usable practical rotation rates is 0.25–3 Hz [rps] which allows a wide range of RRM and ARMROT characteristics to be utilized (at 100 mT AF field, 100 μT bias field). Sets of magnetic mineral extracts from sediments, and well characterized rock samples that contain the key magnetic minerals magnetite, pyrrhotite and greigite are used for a calibration of the RRM-ARMROT behaviour. Detrital pyrrhotite and pyrrhotite-bearing phyllites have largely small positive effective field (Bg) values (up to 6 μT), with differences in Bg and ARMROT ratios at 0.5 and 2.5 Hz [rps] allowing grain size discrimination. The positive Bg values, and changes in RRM and ARMROT with rotation rates allow distinction of pyrrhotite from magnetite and diagenetic greigite. Diagenetic greigite has Bg values of –83 to –109 μT (at 0.5 Hz [rps]) and unusual RRM variation at low rotation rates caused by anisotropy affects. In contrast to previous work, based on crushed and sized natural magnetite at high spin rates, Bg for single domain magnetite from intact bacterial magnetofossils from Upper Cretaceous Chalk has some of the lowest Bg (0–1 μT) and displays a steep decline in ARMROT with increasing rotation rates. A simple tool for particle size characterization of magnetite may be the ratio of ARMROT at spin rates 2.5 and 0.5 Hz [rps]. Stability of RRM is better studied using RRM acquisition with increasing AF field intensity, since static demagnetization imparts a nuisance gyroremanence along the field axis. Mineral microstructure, dislocations and particle interactions are likely additional effects on RRM behaviour that need more investigation.

The Global Stratotype Section and Point (GSSP) for the base of the Kimmeridgian Stage (Jurassic System), at Flodigarry, Staffin Bay, Isle of Skye, Scotland, UK Journal Item How to cite: Wierzbowski, Andrzej; Barski, Marcin; Coe, Angela L.; Hounslow, Mark W.; Matyja, Bronisław A.; Price, Gregory D.; Wierzbowski, Hubert; Wright, John K.; Atrops, with contributions from Francois; Grabowski, Jacek; Mattioli, Emanuela; Morton, Nicol; Ogg, James G.; Olóriz, Federico; Page, Kevin; Parent, Horacio; Przybylski, Piotr; Schweigert, Guenter and Villaseñor, Anna Bertha (2023). The Global Stratotype Section and Point (GSSP) for the base of the Kimmeridgian Stage (Jurassic System), at Flodigarry, Staffin Bay, Isle of Skye, Scotland, UK. Episodes (Early Access).

A *.zip file containing four files for Worked example 17.1 from the book Deciphering Earth’s History: the Practice of Stratigraphy, which demonstrate the application of sequence slotting with palaeontological data using the CPLSlot freeware. There are two input data text files (ending in extension *.txt) of the palynological data for the two successions to be correlated, a third file (extension *.sld), which can only be read by CPLSlot, that stores information about correlation and slotting models set up when using the software, while the fourth file, an Excel file (extension *.xlsx), contains the complete workings for Worked example 17.1, and the last processing step of finalizing a correlation model not show in the worked example in the book.