A revised tropical to subtropical paleogene planktonic foraminiferal zonation

Author Posting. © Cushman Foundation for Foraminiferal Research, 2005. This article is posted here by permission of Cushman Foundation for Foraminiferal Research for personal use, not for redistribution. The definitive version was published in Journal of Foraminiferal Research 35 (2005): 279-298, doi:10.2113/35.4.279.New biostratigraphic investigations on deep sea cores and outcrop sections have revealed several shortcomings in currently used tropical to subtropical Eocene planktonic foraminiferal zonal schemes in the form of: 1) modified taxonomic concepts, 2) modified/different ranges of taxa, and 3) improved calibrations with magnetostratigraphy. This new information provides us with an opportunity to make some necessary improvements to existing Eocene biostratigraphic schemes. At the same time, we provide an alphanumeric notation for Paleogene zones using the prefix ‘P’ (for Paleocene), ‘E’ (for Eocene) and ‘O’ (for Oligocene) to achieve consistency with recent short-hand notation for other Cenozoic zones (Miocene [’M’], Pliocene [PL] and Pleistocene [PT]). Sixteen Eocene (E) zones are introduced (or nomenclaturally emended) to replace the 13 zones and subzones of Berggren and others (1995). This new zonation serves as a template for the taxonomic and phylogenetic studies in the forthcoming Atlas of Eocene Planktonic Foraminifera (Pearson and others, in press). The 10 zones and subzones of the Paleocene (Berggren and others, 1995) are retained and renamed and/or emended to reflect improved taxonomy and an updated chronologic calibration to the Global Polarity Time Scale (GPTS) (Berggren and others, 2000). The Paleocene/Eocene boundary is correlated with the lowest occurrence (LO) of Acarinina sibaiyaensis (base of Zone E1), at the top of the truncated and redefined (former) Zone P5. The five-fold zonation of the Oligocene (Berggren and others, 1995) is modified to a six-fold zonation with the elevation of (former) Subzones P21a and P21b to zonal status. The Oligocene (O) zonal components are renamed and/or nomenclaturally emended

Upper Paleocene-Lower Eocene biostratigraphy of Darb Gaga, Southeastern Kharga Oasis Western Desert, Egypt

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of African Earth Sciences 118 (2016): 12-23, doi:10.1016/j.jafrearsci.2016.02.016.Paleontological studies on the Upper Paleocene-Lower Eocene succession at Darb Gaga, southeastern Kharga Oasis, Western Desert, Egypt document the changes associated with the Paleocene-Eocene Thermal Maximum (PETM), such as 1) a radical alteration of the relative and absolute abundance of planktonic foraminifera; 2) a massive occurrence of the excursion planktonic foraminiferal taxa; 3) a widespread deposition of calcarenite yielding atypical (extremely high) faunal abundance associated with the younger phase of warming; and 4) a concentration of coprolites associated with the middle phase of warming. We also document the Lowest Occurrence (LO) of dimorphic larger benthic and excursion foraminifera during the earlier phase of warming at Darb Gaga, as recorded in Bed 1 of the Dababiya Quarry Member. The absence of these faunas in Bed 1 at Dababiya (the GSSP for the P/E Boundary) is likely to be due to both intense deficiency in dissolved oxygen and massive carbonate dissolution. Only remains (fish remains) of faunas that can tolerate the toxicity produced by low oxygen conditions are found in the stratigraphic record of this (oldest) phase at Dababiya. The Dababiya Quarry Member (DQM) at Darb Gaga reflects the unfolding of the sedimentary and biotic changes associated with the PETM global warming at, and following, the Paleocene/Eocene boundary on the southern Tethys platform. The changes began with a rapid increase in bottom and “intermediate” water temperature. The temperature increase was accompanied by removal of oxygen during the early and middle stages of warming. This led to the absence of both subbotinids and calcareous benthic foraminifera in the early and second coprolite-bearing phases (Beds 2 and 3 of the DQM). Dissolution seems to have no role during these stages as shown by the unusual abundance and good preservation of the warm-tolerant Ac. sibaiyaensis. This species reaches its maximum abundance in Bed 2 where it exhibits a broad range of size (63-250 μm) and shape that probably reflect optimal growth under the warmest water conditions. Thus, we infer that temperature and dissolved oxygen content of the sea-water were the main factors controlling the distribution pattern(s) of the microplankton and microbenthos during the PETM.2017-02-2

The Neogene: Part 2: Neogene geochronology and chronostratigraphy

We present a revised Neogene geochronology based upon a best fit to selected high temperature radiometric dates on a number of identified magnetic polarity chrons (within the late Cretaceous, Paleogene, and Neogene) which minimizes apparent accelerations in sea-floor spreading. An assessment of first order correlations of calcareous plankton biostratigraphic datum events to magnetic polarity stratigraphy yields the following estimated magnetobiochronology of major chronostratigraphic boundaries: Oligocene/Miocene (Chron C6CN): 23.7 Ma; Miocene/Pliocene (slightly younger than Gilbert/Chron 5 boundary): 5.3 Ma; Pliocene/Pleistocene (slightly younger than Olduvai Subchron): 1.6 Ma. Changes to the marine time-scale are relatively minor in terms of recent and current usage except in the interval of the middle Miocene where new DSDP data reveal that previous correlations of magnetic anomalies 5 and 5A to magnetic polarity Chrons 9 and 11, respectively, are incorrect. Our revized magnetobiostratigraphic correlations result in a 1.5-2 m.y. shift towards younger magnetobiochronologic age estimate in the middle Miocene. Radiometric dates correlated to bio- and magnetostratigraphy in continental section generally support the revized marine magnetobiochronology presented here. Major changes, however, are made in marine-non-marine correlations in the Miocene in Eurasia which indicate African-Eurasian migrations through the Persian Gulf as early as 20 Ma. The 12.5 Ma estimate of the Hipparion datum is supported by recent taxonomic revisions of the hipparions and magnetobiostratigraphic correlations which show that primitive hipparions first arrived in Eurasia and North Africa at c. 12.5 Ma and a second wave in the tropics (i.e. Indian and central Africa) at c. 10 Ma

Jurassic to Paleogene: Part 2: Paleogene geochronology and chronostratigraphy

We present a revised Paleogene geochronology based upon a best fit to selected high temperature radiometric dates on a number of identified magnetic polarity chrons (within the late Cretaceous, Paleogene and Neogene) which minimizes apparent accelerations in sea-floor spreading. An assessment of first order correlations of calcareous plankton biostratigraphic datum events to magnetic polarity stratigraphy yields the following estimated magnetobiochronology of major chronostratigraphic boundaries: Cretaceous-Tertiary boundary (Chron C29R), 66.4 Ma; Paleocene-Eocene (Chron C24R), 57.8 Ma; Eocene-Oligocene (Chron C13R), 36.6 Ma; Oligocene-Miocene (Chron C6CN), 23.7 Ma. The Eocene is seen to have expanded chronologically (~ 21 m.y.) at the expense of the Paleocene (~ 9 m.y.) and is indeed the longest of the Cenozoic epochs. In addition, magnetobiostratigraphic correlations require adjustments in apparent correlations with standard marine stage boundaries in some cases (particularly in the Oligocene). Finally, we present a correlation between standard Paleogene marine and terrestrial stratigraphies

The impact of orbitally forced upwelling on Oligocene planktic foraminifera δ13C and abundances

Abstrac

Kinetic-inductance-limited reset time of superconducting nanowire photon counters

We investigate the recovery of superconducting NbN-nanowire photon counters after detection of an optical pulse at a wavelength of 1550 nm, and present a model that quantitatively accounts for our observations. The reset time is found to be limited by the large kinetic inductance of these nanowires, which forces a tradeoff between counting rate and either detection efficiency or active area. Devices of usable size and high detection efficiency are found to have reset times orders of magnitude longer than their intrinsic photoresponse time.Comment: Submitted to Applied Physics Letter

Paleogene time scale miscalibration: Evidence from the dating of the North Atlantic igneous province

Jolley et al. (2002) have proposed that the date of the Paleocene - Eocene thermal maximum is ca. 60 Ma, at least 5 m.y. older than currently estimated and, as a result, argue that the Paleogene time scale of Berggren et al. (1995) is grossly miscalibrated. The implications of this proposal are implausible, and we attribute the discrepancy in age noted by Jolley et al. (2002) to miscorrelation of the Staffa-type palynofloras and ambiguous isotopic dates from the North Atlantic igneous province

Subseries/Subepochs approved as a formal rank in the international stratigraphic guide

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Aubry, M., Head, M. J., Piller, W. E., & Berggren, W. A. Subseries/Subepochs approved as a formal rank in the international stratigraphic guide. Episodes, 43(4), (2020): 1041-1044, doi:10.18814/epiiugs/2020/020066.The International Subcommission on Stratigraphic Classification, as the constituent body of the International Commission on Stratigraphy (ICS) responsible for the International Stratigraphic Guide, has voted to include the subseries/ subepoch as a formal rank in the next edition of the Guide. This acknowledges the recent ratification of formal subseries and their corresponding stages for the Holocene Series/Epoch but allows individual subcommissions within ICS the freedom to decide whether or not to adopt this rank for their particular stratigraphic/time interval.We are grateful to the ISSC membership for discussions and to Secretary Jochen Erbacher for organizing the vote; to Mike Walker for sharing an unpublished manuscript with us; to the many colleagues who have expressed their support for formalization of subseries; and to Dennis Kent and an anonymous reviewer for their reviews of the manuscript

Nonlinear resonant behavior of the dispersive readout scheme for a superconducting flux qubit

A nonlinear resonant circuit comprising a SQUID magnetometer and a parallel capacitor is studied as a readout scheme for a persistent-current (PC) qubit. The flux state of the qubit is detected as a change in the Josephson inductance of the SQUID magnetometer, which in turn mediates a shift in the resonance frequency of the readout circuit. The nonlinearity and resulting hysteresis in the resonant behavior are characterized as a function of the power of both the input drive and the associated resonance peak response. Numerical simulations based on a phenomenological circuit model are presented which display the features of the observed nonlinearity.Comment: 9 pages, 9 figure

Oligocene-Miocene biostratigraphy, magnetostratigraphy, and isotopic stratigraphy of the western North Atlantic

Magnetostratigraphic records from western North Atlantic Deep Sea Drilling Project (DSDP) Sites 563 and 558 are correlated with the geomagnetic polarity time scale (GPTS; Berggren et aI., 1984a, 1984b) using marine magnetic anomalies and selected biostratigraphic datum levels. The magnetochronology established is used to make direct magnetobiostratigraphic correlations that agree with previous Oligocene-early Miocene studies. However, we show that Zones NN8 partim and NN9 and associated Epoch 11 correlate with Magnetic Anomaly 5 (= Chron C5n). This contrasts with previous indirect correlations of Epoch 11 with Anomaly 5A and requires an upward adjustment of 1.5-2.0 m.y. for middle-late Miocene calcareous nannofossil zones. We correlate the middle/late Miocene boundary with Zone NN8 and earliest Chron C5n (10.4 Ma)