Abstract: In 1841, Murchison coined the term Permian for strata in the Russian Urals. Recognition of the Permian outside of Russia and central Europe soon followed, but it took about a century for the Permian to be accepted globally as a distinct geological system. The work of the Subcommission on Permian Stratigraphy began in the 1970s and resulted in current recognition of nine Permian stages in three series: the Cisuralian (lower Permian) – Asselian, Sakmarian, Artinskian and Kungurian; the Guadalupian (middle Permian) – Roadian, Wordian and Capitanian; and the Lopingian (upper Permian) – Wuchiapingian and Changhsingian. The 1990s saw the rise of Permian conodont biostratigraphy, so that all Permian Global Stratigraphic Sections and Points (GSSPs) use conodont evolutionary events as the primary signal for correlation. Issues in the development of a Permian chronostratigraphic scale include those of stability and priority of nomenclature and concepts, disagreements over changing taxonomy, ammonoid v. fusulinid v. conodont biostratigraphy, differences in the perceived significance of biotic events for chronostratigraphic classification, and correlation problems between provinces. Further development of the Permian chronostratigraphic scale should focus on GSSP selection for the remaining, undefined stage bases, definition and characterization of substages, and further integration of the Permian chronostratigraphic scale with radioisotopic, magnetostratigraphic and chemostratigraphic tools for calibration and correlation.

In 1907, Barnum Brown named the Hell Creek beds (Formation) for the strata exposed in the Hell Creek Valley and other downstream tributaries of the Missouri River. In the absence of a stratotype section, a lectostratotype is herein proposed for the Hell Creek Formation based on 84.2-m-thick exposures at Flag Butte (local name) in Ried Coulee (archaic use; East Fork of Hell Creek) and East Ried Coulee, tributaries of Hell Creek, Garfield County, Montana (sec. 29, T. 21 N., R. 38 W., NAD27 CONUS; base 47.55931°N, 106.88111°W; top 47.55533°N, 106.86810°W). The formation is underlain with general conformity by sandstone beds of the Fox Hills Formation (as characteristically known, the Colgate Member is absent) and is for the most part conformably overlain locally by the Tullock Member of the Fort Union Formation. The upper contact at Flag Butte is demarcated at the base of the IrZ lignite bed (above an iridium anomaly). The boundary has been demonstrated to be somewhat unconformable in areas to the west. The IrZ bed is also missing at Bug Creek in McCone County. In its type section, the Hell Creek Formation is subdivided (simply and informally) into Ried Coulee (lower Hell Creek), East Ried Coulee (middle Hell Creek), and Flag Butte (upper Hell Creek) units, each containing a sandstone and a mudstone lithofacies. Formational thickness varies with local depositional and erosional history of various coastal-deltaic environments across the Williston Basin and a trend of overall thinning to the east and northeast.

Abstract The Bridger Formation is located in the Green River basin in southwest Wyoming, and the Uinta and Duchesne River formations are located in the Uinta basin in Utah. These three rock units and their diverse fossil assemblages have great scientific importance and are also of historic interest to vertebrate paleontologists. Notably, they are also the stratotypes for the three middle Eocene North American Land Mammal “Ages,” the Bridgerian, Uintan, and Duchesnean, from oldest to youngest. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning ~10 million years (49–39 Ma). This article features a detailed field excursion through portions of the Green River and Uinta basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional and paleoenvironmental history, and the history of scientific exploration.

The Ancona Penrose Conference of October 2007 dealt with the current state of understanding of the late Eocene and the Eocene-Oligocene boundary, ~34 million years ago, a critical but very brief interval in Earth history. In this paper, we place that brief interval and the lessons from the conference in the broadest possible context by viewing them in the light of “Big History.” This new intellectual concept maintains that there may be value in considering the entire past, from the big bang until today, as a single unit of study. At this very early stage in the study of Big History, not even the most fundamental questions have been well formulated, let alone answered. As a first cut, Big History can be divided into regimes by considering the disciplines that study it: cosmic history (studied by cosmology and astronomy), Earth history (studied by geology), life history (studied by paleontology and evolutionary biology), and human history (studied by archaeology and historiography). These disciplines differ in terms of problems, techniques, and intellectual traditions. If we seek a common basis for a finer subdivision, the changes in utilization of the energy that have driven historical changes would seem like a good candidate. In two thought-provoking papers in 2007, Robert Aunger proposed “periodizing” all of history by placing divisions between periods when new methods of utilizing concentrated energy came into being, e.g., cellular metabolism or human agriculture. Aunger draws a parallel between this periodization of Big History and the establishment of the geological time scale. In this paper, we carefully consider this parallel and conclude that periodizing history on the basis of energy use or any other conceptual scheme is quite different from the division of Earth history into the intervals that yielded the geological time scale. Both are important but they have different purposes. Time-scale construction is a procedure that ties history to the rocks that record the history. It is a necessary step in reconstructing Earth and life history but is neither necessary nor possible in studying the history of cosmos or humanity. In contrast, periodizing history into intervals provides a conceptual framework on which to hang a growing understanding of history. We conclude that it is important to differentiate between (1) time-scale construction, (2) correlating events, (3) dating events, and (4) periodizing history. In this light, Aunger’s focus on changes in energy use remains an instructive way of periodizing history, but it must be clearly differentiated from time-scale construction.

The Eocene-Oligocene transition marks the passage from “greenhouse” conditions to an “icehouse state” with progressive global cooling starting in the early middle Eocene. The late Eocene is also characterized by a high concentration of extraterrestrial impacts, the effects of which, on living organisms and climatic changes, are still not understood. We carried out a high-resolution investigation on planktonic foraminiferal assemblages in an 8-m-thick segment of the Massignano global stratotype section and point for the Eocene-Oligocene boundary with the aim of assessing the effects that the impacts may have had on the environment and this group of organisms. The studied interval is punctuated by three late Eocene iridium-rich layers, several cosmic signatures, and enhanced levels of 3 He. The two lower closely spaced iridium anomalies are possibly linked to the Popigai and Chesapeake Bay impact events, respectively, whereas no particular impact event can be assigned to the third anomaly, even if it might be correlated with some large craters. Interpretation of data suggests that all the impacts had no abrupt, dramatic effects on planktonic foraminifera. However, acting as forcing factors, they induced some environmental perturbations and may have contributed to remarkable climate changes superimposed on the general late Eocene cooling trend. The Popigai and Chesapeake Bay impact events triggered significant changes in the water mass structure, in terms of stratification and trophic resources, associated with some climatic excursions that took place within chron C16n.1n and chron C15r and at the transition between planktonic foraminiferal zones P15 and P16. The short-term warming pulse recognized after the Popigai impact might have been due to greenhouse effects produced by injection of CO 2 into the atmosphere and/or the release of methane hydrate after the impact itself. The dynamic between hydrological and climate changes across the impactoclastic layers as observed at Massignano displays different features at each impact event, probably due to the context in which each occurred in terms of impactor size, location, and target rocks. The relatively long duration of the enhanced cooling following the Chesapeake Bay impact suggests that this event induced a progressive cooling and triggered a feedback mechanism that sustained the initial impact-induced changes. Similar patterns of climatic excursions reported worldwide across the equivalent impact-ejecta horizons indicate that the impact-induced climate changes recorded at Massignano appear to be global in extent.

High-resolution spectral analyses of four climate proxies from Massignano, Italy (Eocene-Oligocene boundary global stratotype section and point [GSSP]), indicate that the deposition of this rhythmically bedded sedimentary sequence was controlled by Milankovitch orbital cycles. An inverse relationship between the magnetic susceptibility record and the co-varied calcium carbonate, δ 18 O, and δ 13 C records is indicative of a climate model in which limestones represent dry/cold periods, while marly limestones represent warm/wet periods. Through pattern matching of band-pass filtered signals with the La2004 eccentricity curve, we propose an astrochronological calibration for this important time period. Constrained by three radioisotopically dated volcanic ashes and based on a band-pass version of eccentricity that exhibits expected amplitude modulations, our astrochronology yields a refined age for the Eocene-Oligocene boundary of 33.91 ± 0.05 Ma. Orbital forcing is less pronounced in the lower portion of the Massignano section (meter levels 0–15), which contains evidence of several impact events and a 2.2-m.y.-long comet/asteroid shower. We propose that substantial, nonperiodic climate alterations caused by this period of enhanced extraterrestrial activity mask the Milankovitch climate cycles. Possible mechanisms for the exaggeration of impact-related climatic changes include the ice-albedo feedback or the combined effect of impact-related atmospheric alterations with ongoing dust-particle loading associated with the comet/asteroid shower.

The interval from the middle Eocene to early Oligocene represents one of the most significant transitions in Earth’s climate, during which greenhouse conditions were supplanted by icehouse conditions of the present day. This global transition was preceded by a long-term cooling phase and short-term uncorrelated variations in several marine proxies, which indicate paleoceanographic instabilities prior to the key climatic transition. We integrate previous multidisciplinary studies with recent data from the Massignano section (Umbria-Marche Basin) and summarize interpretations of studies from the past 20 yr that have been based on the Eocene-Oligocene boundary global stratotype section and point (GSSP). Based on the many data sets from this section, with an emphasis on the rock magnetic data, we propose that the fluctuations and final cessation of a westward subtropical Eocene Neotethys (STENT) current were drivers in the climatic transition from greenhouse to icehouse conditions. Our hypothesis considers that the global variable climatic conditions were synchronous to large changes in circulation in the western Neotethys Ocean, which were primarily due to paleogeographic and sea-level changes. Specifically, the closing of the gateway between the Arabian and Eurasian plates, through coupling of sea-level changes, could represent the threshold or one of the triggers that caused the paleoceanographic variations in the Neotethys and in global ocean circulation patterns during the end of the Eocene.

We present the results of integrated biostratigraphic (planktonic foraminifera, calcareous nannofossils, and dinoflagellates), magnetostratigraphic, and cyclostratigraphic analyses of the lower part of Monte Cagnero section (Umbria-Marche Apennines of Italy), a continuous and complete succession of pelagic limestone and marls that provides the means for an accurate and precise astrochronologic calibration of the Eocene-Oligocene transition. This 38.5-m-thick section overlaps the Oligocene section, which, at meter level 188, contains the Rupelian-Chattian boundary corresponding to the O4-O5 planktonic foraminiferal zonal boundary within the upper half of magnetochron C10n. The Eocene-Oligocene boundary at Monte Cagnero, as defined by the last occurrence of hantkeninid planktonic foraminifers (E14-E15 zonal boundary), is found at meter level 114.1, in the upper part of calcareous nannofossil zone CP16a, and very near the Aal-Gse dinocyst zonal boundary. Paleomagnetic analysis has identified all the magnetic reversals from the lower C13r to the lower C12n, precisely overlapping the base of the Oligocene magnetostratigraphic succession and placing the Eocene-Oligocene boundary in the upper part of C13r, in full agreement with the global stratotype section and point (GSSP) at Massignano. Spectral analysis of calcium carbonate data from bulk samples, collected at 5 cm intervals, indicates that orbital forcing of depositional cycles (i.e., limestone versus marl alternations) is dominant at frequencies corresponding to the theoretical astronomical curves of eccentricity, obliquity, and precessional cycles throughout the studied Eocene-Oligocene transition. Correlation with the astrochronologic time scale allows an age assignment of 33.95 Ma for the Eocene-Oligocene boundary, which is in close agreement with the astrochronologic age for the boundary in the GSSP of Massignano obtained in a similar study by R.E. Brown and colleagues in this volume. Thus, the Monte Cagnero section represents a candidate parastratotype for the Eocene-Oligocene GSSP of Massignano in the eventuality that the oxygen and carbon stable isotope shifts defining the oxygen isotope Oi-1 glaciation will be preferred over the last occurrence of hantkeninids as marker for the boundary, since, at Massignano, the beginning of this isotope shift is barely represented in the uppermost part of the exposed section. The excellent integrated stratigraphic framework of Monte Cagnero presented here will significantly facilitate further high-resolution isotope and paleoecological studies across the time of transition from a hothouse to icehouse Earth.

The Upper Triassic (Carnian–Norian) Martin Bridge Formation of northeastern Oregon, southeastern Washington, and western Idaho is characterized by rapidly shifting depositional processes within a tropical volcanic island arc setting. Martin Bridge sequences in the Hells Canyon and northern Wallowa Mountains document shallow-water peritidal evaporitic sediments that are succeeded by deeper and predominantly subtidal deposits. This indicates drowning of the carbonate platform and a transition to deeper-water turbiditic sedimentation before a late Triassic transition into the overlying mid-Norian to Jurassic Hurwal Formation. At the type locality in the southern Wallowa Mountains, dysaerobic shales, carbonate debris sheets, and turbiditic sediments indicate distal slope and basinal environments while other facies at other sites in the Wallowa Mountains and Hells Canyon areas indicate reef and shallow-water platform settings. In this paper we formally recognize the name Martin Bridge Formation and reinstate the type locality in the southern Wallowa Mountains as the principal unit strato-type. An additional reference section is given at Hurricane Creek in the northern Wallowa Mountains. The Martin Bridge is formally divided into four members: the Eagle Creek and Summit Point Members are introduced and formally proposed herein and the BC Creek and Scotch Creek Members also are elevated to formal status. A partial reconstruction of the Wallowa terrane during deposition of the Martin Bridge Formation suggests a north-south (or northeast-southwest) trending platform margin facing a forearc basin situated to the east (or southeast). The lithofacies and paleontological characteristics of the Martin Bridge can be put into the framework of a depositional and a tectonic model to help better explain many of the stratigraphic and paleontologic problems previously encountered. We believe that the Wallowa terrane provides one of the best and most complete examples yet known for shallow-water carbonate depositional patterns in an oceanic island arc setting.

The Pierre Shale, a member of the Montana Group, is extensively exposed throughout the Northern Great Plains and is well exposed along the Missouri River Trench in central South Dakota. Currently, the Pierre Shale is of formational rank, but herein it is elevated to group status and should be termed the Pierre Shale Group. Most current members of the Pierre Shale should be elevated to formational rank, as they are of distinctive lithology and are mappable throughout the Missouri River area and elsewhere. The name Montana Group should be abandoned because of its relatively limited lithostratigraphic utility. Extensive geological and paleontological investigations of the lower Missouri River Trench indicate that a number of previously described units should be subdivided. In particular, the lowest described unit of the Pierre Shale along the Missouri River, the Sharon Springs, exhibits three distinct disconformity-bounded lithostratigraphic units that are newly designated as members. The lowermost unit is distinguished by bentonites, and the upper two units can be observed in the type area of the Sharon Springs in western Kansas. The lowermost unit is characterized by numerous bentonite beds similar to the Ardmore bentonitic succession in the southern Black Hills, is normally disconformably superjacent to the Niobrara Formation, may be absent where degraded, and is named the Burning Brule Member. The overlying middle unit within the Sharon Springs consists of a siliceous shale that weathers vertically and is termed the Boyer Bay Member, whereas the upper unit is a bentonitic shale characterized by gypsiferous phosphatic concretions and is named the Nicholas Creek Member. These three units are herein regarded as new members of a hierarchically elevated Sharon Springs Formation. Other currently recognized members of the Pierre Shale in central South Dakota should likewise be elevated to formation-rank units except for the Crow Creek Member, a relatively thin tan siltstone. Because this unit is not mappable at recognized scales, it should be retained as a member of the DeGrey Formation. Inclusion of the Crow Creek Member within the DeGrey Formation is based upon another sporadically occurring tan siltstone that lies stratigraphically lower, and the intervening shales are similar to those of the lower DeGrey Formation. The Pierre Shale members should also be elevated to formational status in North Dakota, Kansas, and around the Black Hills in eastern Wyoming and western South Dakota. The elevation of units should probably be made throughout the Pierre Shale depositional area, but those decisions should be made by local investigators.

The position of the Lower–Middle Cambrian boundary, as classically used, is an issue still under discussion by the International Subcommission on Cambrian Stratigraphy (ISCS), and no level has been established yet. At present, there are two oryctocephalid trilobite species–based Global Standard Stratotype-section and Point (GSSP) proposals in the literature, Oryctocephalus indicus and Ovatoryctocara granulata . These two species have not yet been found in the Mediterranean subprovince. For this reason, other correlation tools that approximate these levels are needed. A complete chronostratigraphy for the Lower and Middle Cambrian Series of Iberia was proposed by Sdzuy (1971a , b ). Recently Geyer and Landing (2004) made a new proposal for the Lower–Middle Cambrian chronostratigraphy of West Gondwana. They proposed the Agdzian Stage. This stage is more or less equivalent to the Bilbilian and Leonian Stages of Spain. The main problem with the Agdzian Stage is that its boundaries are not correlative with a potential global Cambrian Series boundary. Those levels would be in the middle part of the Agdzian Stage. In order to make a more accurate correlation, we prefer to use the previous Spanish scale and try to clarify the correlation between different sequences of this time interval in the Mediterranean subprovince. Here we present a summary of biostratigraphical data from the Bilbilian and Leonian Stages, the boundary of which is placed at the first appearance datum (FAD) of Acadoparadoxides mureroensis . This, the classical Lower–Middle Cambrian boundary in the Paradoxides realm, is constrained by the data of various areas of the Mediterranean region. A revised correlation chart comparing the Mediterranean and other regions is presented. The position of the Bilbilian–Leonian boundary roughly coincides with the two GSSPs proposed by the ISCS.

The Majalcorón Formation (Paleocene) is an unusual lithostratigraphic unit mainly made up of calcarenites with reworked Microcodium . Analysis of this unit from different localities of the Subbetic (southern Spain) shows that the formation is interbedded in pelagic sedimentary rocks. Calcareous nannofossils in the latter confirm that deposition of the Majalcorón Formation began in the early Danian and finished in the latest Danian–early Selandian. The reworked Microcodium calcarenites are grainstones mainly constituting disaggregated Microcodium prisms and sparite cement. Secondarily, they contain quartz grains, glauconite, mud clasts, benthonic and planktonic foraminifera, coal fragments, and plant remains. In some beds, hummocky cross-stratification and mound-shaped structures appear. The reworked Microcodium calcarenites are derived from the erosion of calcareous paleosols in source areas located to the north. A eustatic regressive-transgressive-regressive succession at the Cretaceous-Tertiary boundary and in the early Paleocene is responsible for the beginning of the Microcodium paleosol development. Sedimentation of the calcarenites took place in a shallow marine ramp after erosion of the paleosols, and ended with the development of paleokarstic features on the top of the formation. This interpretation of the Majalcorón Formation as a shallow-marine deposit is important to the understanding of the paleogeography and depositional paleobathymetry of the adjacent pelagic facies during the Late Cretaceous and Paleogene. Se estudia una unidad estratigráfica peculiar, la Formación Majalcorón del Paleoceno en el Subbético, compuesta mayoritariamente por calcarenitas con Microcodium retrabajado. Esta unidad se encuentra intercalada entre rocas sedimentarias pelágicas con nanoplancton calcáreo que ha permitido establecer que su depósito comenzó en el Daniense inferiory finalizó en el Daniense terminal–Selandiense inferior. Lascalcarenitas de Microcodium resedimentado son grainstones compuestos mayoritariamente por prismas disgregados de Microcodium y cemento esparítico. Además hay granos de cuarzo, glauconita, intraclastos micríticos, foraminíferos planctónicos y bentónicos, y fragmentos de plantas. En algunos estratos aparece estratificación cruzada de tipo hummocky y estructuras en montículo. Las calcarenitas de Microcodium proceden de la erosión de paleosuelos calcáreos. Se propone que las áreas fuente que proporcionaron los importantes volúmenes de Microcodium se localizaban al norte, en el Subbético Externo. Cambios eustáticos del nivel del mar en el límite Cretácico-Terciario y en el Paleoceno inferior, en una sucesión regresiva-transgresiva-regresiva fueron los principales responsables del comienzo del desarrollo de los paleosuelos con Microcodium , de la sedimentación de las calcarenitas después de la erosión de los paleosuelos y del final de su depósito con el desarollo de rasgos paleokársticos en el techo de la formación. La consideración de la Formación Majalcorón como un depósito marino somero es importante para interpretar la paleogeografía y paleobatimetría de las facies pelágicas adyacentes durante el Cretácico Superior y Paleógeno.