This report summarizes the international divisions and ages in the Geologic Time Scale, published
in 2012 (GTS2012). Since 2004, when GTS2004 was detailed, major developments have taken place
that directly bear and have considerable impact on the intricate science of geologic time scaling. Precam brian
now has a detailed proposal for chronostratigraphic subdivision instead of an outdated and abstract chronometric
one. Of 100 chronostratigraphic units in the Phanerozoic 63 now have formal definitions, but stable
chronostratigraphy in part of upper Paleozoic, Triassic and Middle Jurassic/Lower Cretaceous is still wanting.
Detailed age calibration now exist between radiometric methods and orbital tuning, making 40Ar-39Ar dates
0.64% older and more accurate. In general, numeric uncertainty in the time scale, although complex and not
entirely amenable to objective analysis, is improved and reduced. Bases of Paleozoic, Mesozoic and Cenozoic
are bracketed by analytically precise ages, respectively 541 0.63, 252.16 0.5, and 65.95 0.05 Ma.
High-resolution, direct age-dates now exist for base-Carboniferous, base-Permian, base-Jurassic, base-Cenomanian
and base-Eocene. Relative to GTS2004, 26 of 100 time scale boundaries have changed age, of which
14 have changed more than 4 Ma, and 4 (in Middle to Late Triassic) between 6 and 12 Ma. There is much
higher stratigraphic resolution in Late Carboniferous, Jurassic, Cretaceous and Paleogene, and improved integration
with stable isotopes stratigraphy. Cenozoic and Cretaceous have a refined magneto-biochronology.
The spectacular outcrop sections for the Rosello Composite in Sicily, Italy and at Zumaia, Basque Province,
Spain encompass the Global Boundary Stratotype Sections and Points for two Pliocene and two Paleocene
stages. Since the cycle record indicates, to the best of our knowledge that the stages sediment fill is stratigraphically
complete, these sections also may fulfill the important role of stage unit stratotypes for three of
these stages, Piacenzian, Zanclean and Danian

On The Geologic Time Scale

Use of U–Pb ages of detrital zircons to infer maximum depositional ages of strata: A test against a Colorado Plateau Mesozoic database

The role of fossils in dating the tree of life has been misunderstood. Fossils can provide good "minimum" age estimates for branches in the tree, but "maximum" constraints on those ages are poorer. Current debates about which are the "best" fossil dates for calibration move to consideration of the most appropriate constraints on the ages of tree nodes. Because fossil-based dates are constraints, and because molecular evolution is not perfectly clock-like, analysts should use more rather than fewer dates, but there has to be a balance between many genes and few dates versus many dates and few genes. We provide "hard" minimum and "soft" maximum age constraints for 30 divergences among key genome model organisms; these should contribute to better understanding of the dating of the animal tree of life.

/pdf/paleontological-evidence-to-date-the-tree-of-life-5dhwbwgnyr.pdf

Paleontological Evidence to Date the Tree of Life

Carbon stable-isotope variation through the Cenomanian–Santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven Chalk successions in England. The sections show consistent stratigraphic trends and δ13C values that provide a basis for highresolution correlation. Positive and negative δ13Cexcursions and inflection points on the isotope profiles are used to define 72 isotope events. Key markers are provided by positive δ13C excursions of up to + 2‰: the Albian/CenomanianBoundary Event; Mid-Cenomanian Event I; theCenomanian/Turonian Boundary Event; the Bridgewick, Hitch Wood and Navigation events of Late Turonian age; and the Santonian/Campanian Boundary Event. Isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons. An age-calibrated composite δ13C reference curve and an isotope event stratigraphy are constructed using data from the English Chalk. The isotope stratigraphy is applied to successions in Germany, France, Spain and Italy. Correlation with pelagic sections at Gubbio, central Italy, demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the Cenomanian–Turonian stages, confirming established relationships between Tethyan planktonic foraminiferal and Boreal macrofossil biozonations. Correlation of the Coniacian–Santonian stages is less clear cut: magnetostratigraphic evidence for placing the base of Chron 33r near the base of the Upper Santonian is in good agreement with the carbon-isotope correlation, but generates significant anomalies regarding the placement of the Santonian and Campanian stage boundaries with respect to Tethyan planktonic foraminiferal and nannofossil zones. Isotope stratigraphy offers a more reliable criterion for detailed correlation of Cenomanian–Santonian strata than biostratigraphy.With the addition of Campanian δ13C data from one of the English sections, a composite Cenomanian–Campanian age-calibrated reference curve is presented that can be utilized in future chemostratigraphic studies. 
The Cenomanian–Campanian carbon-isotope curve is remarkably similar in shape to supposedly eustatic sea-level curves: increasing δ13C values accompanying sea-level rise associated with transgression, and falling δ13C values characterizing sea-level fall and regression. The correlation between carbon isotopes and sea-level is explained by variations in epicontinental sea area affecting organic-matter burial fluxes: increasing shallow sea-floor area and increased accommodation space accompanying sea-level rise allowedmore efficient burial ofmarine organic matter, with the preferential removal of 12C from the marine carbon reservoir. During sea-level fall, reduced seafloor area, marine erosion of previously deposited sediments, and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter, causing falling δ13C values. Additionally, drowning of carbonate platforms during periods of rapid sea-level rise may have reduced the global inorganic relative to the organic carbon flux, further enhancing δ13C values, while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition. Variations in nutrient supply, changing rates of oceanic turnover, and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon-isotope ratios.

/pdf/secular-variation-in-late-cretaceous-carbon-isotopes-a-new-58ie1pbn91.pdf

Secular variation in Late Cretaceous carbon isotopes: a new δ13C carbonate reference curve for the Cenomanian-Campanian (99.6-70.6 Ma)

• Plants have utterly transformed the planet, but testing hypotheses of causality requires a reliable time-scale for plant evolution. While clock methods have been extensively developed, less attention has been paid to the correct interpretation and appropriate implementation of fossil data. • We constructed 17 calibrations, consisting of minimum constraints and soft maximum constraints, for divergences between model representatives of the major land plant lineages. Using a data set of seven plastid genes, we performed a cross-validation analysis to determine the consistency of the calibrations. Six molecular clock analyses were then conducted, one with the original calibrations, and others exploring the impact on divergence estimates of changing maxima at basal nodes, and prior probability densities within calibrations. • Cross-validation highlighted Tracheophyta and Euphyllophyta calibrations as inconsistent, either because their soft maxima were overly conservative or because of undetected rate variation. Molecular clock analyses yielded estimates ranging from 568-815 million yr before present (Ma) for crown embryophytes and from 175-240 Ma for crown angiosperms. • We reject both a post-Jurassic origin of angiosperms and a post-Cambrian origin of land plants. Our analyses also suggest that the establishment of the major embryophyte lineages occurred at a much slower tempo than suggested in most previous studies. These conclusions are entirely compatible with current palaeobotanical data, although not necessarily with their interpretation by palaeobotanists.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2011.03794.x

Establishing a time-scale for plant evolution

The breakup of the former Pangea supercontinent culminated in the modern drifting continents. Increased rifting caused the establishment of the Atlantic Ocean in the middle Jurassic and significant widening in Cretaceous. An explosion of calcareous nannoplankton and foraminifers in the warm seas created massive chalk deposits. A surge in submarine volcanic activity enhanced supergreenhouse conditions in the middle Cretaceous with high CO2 concentrations. Angiosperm plants bloomed on the dinosaur-dominated land during late Cretaceous. The Cretaceous dramatically ended with an asteroid impact, which resulted in a mass extinction.

The Cretaceous Period

Deep marine, fine grained sedimentary strata of Maastrichtian through Miocene age in the Labrador and North Sea sedimentary basins are rich in agglutinated benthic foraminifera. Six new taxa have been found in these regions, several of which also extend to other circum-Atlantic Paleogene localities. The new taxa are: Ammomarginulina aubertae, n. sp. (Maastrichtian to Eocene), Adercotryma agterbergi, n. sp. (middle Eocene to lower Oligocene), Reticulophragmoides jarvisi (Thalmann) emended herein (Paleocene to lower Oligocene), Reticulophragmoides sp. 5 (Oligocene to Miocene), and Spiroplectammina navarroana Cushman emended herein (Maastrichtian to lower middle Eocene). The last occurrences of these taxa are important elements in the high-resolution probabilistic biozonations for the Labrador and North Sea basins.

/pdf/taxonomy-and-biostratigraphy-of-new-and-emended-species-of-4t38kk4ggi.pdf

Taxonomy and biostratigraphy of new and emended species of Cenozoic deep-water agglutinated foraminifera from the Labrador and North Seas

Jurassic Grand Banks foraminifera

A Geologic Time Scale 2004: Preface

The stratigraphic record along the northwestern Australian continental margin provides constraints on the tectonic evolution of the Indo-Australian region, which is characterized by an extremely high level of intraplate deformation, presumably reflecting high levels of regional stress. The patterns of folding and faulting in the northeastern Indian Ocean (shown by focal mechanisms, gravity, and seismic-reflection data) are consistent with predictions of a stress model based on age-dependent driving forces on the lithosphere. Separate compressional and extensional stress provinces are found, each characterized by regionally consistent stress orientations. For example, folding occurs only within the region of predicted deviatoric compression. The evolution of the stress field can be inferred from the stratigraphic data of ODP Leg 116. An unconformity dated at 7.5 Ma marks the end of the recent major phase of folding since which deformation has occurred primarily through faulting. Here, we examine the stratigraphic record of the northwestern margin of Australia using data from Legs 122 and 123 to investigate whether the continental margin stratigraphy records the spatial and temporal variations in stress inferred from the folding in the northeastern Indian Ocean. With the exception of the Pliocene unconformities, the major unconformities inferred from Leg 122 coincide with lowstands in sea level on regional sea-level curves proposed for the northwestern Australian margin, while the major unconformities found during Leg 116 show a lack of correlation with lowstands in these regional curves. Although the correlation of the unconformities from Legs 116 and 122 with lowstands in the Haq et al. (1987) eustatic curve is sometimes good, the major unconformities drilled during Legs 116 and 122 also coincide with plate-tectonic changes of a global character. The Neogene stratigraphic record of the Northwest Shelf can be explained by a paleostress field characterized by an overall tensional stress regime during middle Miocene time to a regime with an increasing level of intraplate compression from late Miocene time onward. The paleostress field inferred from the stratigraphic modeling of the Northwest Shelf is consistent with observed tectonic activity, including middle Miocene fault reactivation in the Browse and Carnarvon basins and Pliocene tilting of the Wombat Plateau. The inferred increase in the level of compression for the northwestern margin occurs at a time corresponding with the onset of compressional folding in the northeastern Indian Ocean, which was documented during Leg 116. The tectono-stratigraphic evolution of the northwestern Australian margin seems to reflect both the changes of intraplate tectonics associated with the unique dynamic situation of the Indo-Australian Plate, as well as the interplay between a major global plate reorganization in Neogene time with eustatic contributions to the sea-level record. INTRODUCTION Since the publication of Vail et al.'s short-term cycles (1977) in relative sea level, major debate has been going on about the inferred global synchroneity of the third-order cycles, both in support of this hypothesis (e.g., Haq et al., 1987) and in opposition (e.g., Parkinson and Summerhayes, 1985; Miall, 1986; Hallam, 1988). Several authors have noted that Vail et al.'s cycles, although based on data from different basins around the world, are heavily weighted in favor of the North Sea and the northern/central Atlantic margins. The issue of global synchroneity is important, as it obviously strongly influences present discussions about the causes of short-term changes in sea level. As noted by Pitman and Golovchenko (1983), tectonic mechanisms (such as variations in spreading rates, hot-spot activity, and orogeny) fail to 1 Gradstein, F. M., Ludden, J. N., et al., 1992. Proc. ODP, Sci. Results, 123: College Station, TX (Ocean Drilling Program). 2 Institute of Earth Sciences, Vrije Universiteit De Boelelaan, 1085, 1081 HV Amsterdam, The Netherlands. Department of Geological Sciences, University of Illinois at Chicago, P.O. Box 4348, Chicago, IL 60680, U.S.A. Bedford Institute of Oceanography, Atlantic Geoscience Centre, Dartmouth, Nova Scotia B2Y 4A2, Canada. 5 Bureau of Mineral Resources, P.O. Box 378, Canberra, ACT 2601, Australia. 6 Bundesanstalt für Geowissenschaften und Rohstoffe, P.O. Box 51054, D-3000 Hannover 51, F.R.G. produce changes at the rate of third-order cycles. This is because such explanations are derivatives of the thermal evolution of the lithosphere and thus are associated with a long thermal inertia of several tens of millions of years. Glacio-eustasy can easily produce both the rate and magnitude of the inferred sea-level changes, but raises two basic problems. First, the occurrence of third-order cycles in sea level during time intervals where no geological evidence can be found suggests low-altitude glaciation. This presents a fundamental problem of explaining changes in eustatic sea level in the Vail et al. (1977) and Haq et al. (1987) charts prior to the late Cenozoic. Second, we see the inability of glacio-eustatics to cause uniform decreases and increases in sea level. The sign and magnitude of the induced sea-level changes depend upon the distance to the location of the ice cap. This feature, well-known among modelers of post-glacial rebound processes (e.g., Lambeck et al., 1987), is not always fully appreciated by those who advocate glacio-eustasy as the key mechanism for explaining global-synchronous changes in sea level of uniform magnitude. More recently, it has been shown that short-term changes in relative sea level can be caused equally well by rapid, stress-induced, vertical motions of the lithosphere in sedimentary basins (Cloetingh et al., 1985; Cloetingh, 1986; Karner, 1986). This research showed that intraplate stresses, as well as being important in the formation of rifted basins (e.g., Houseman and England, 1986), also play a critical part during their subsequent subsidence history. The World Stress Map Project of the Interna-

Felix M. Gradstein

Papers

The Cretaceous Period

Taxonomy and biostratigraphy of new and emended species of Cenozoic deep-water agglutinated foraminifera from the Labrador and North Seas

Jurassic Grand Banks foraminifera

A Geologic Time Scale 2004: Preface

Continental margin stratigraphy, deformation and intraplate stresses for the Indo-Australian region