Jan Hardenbol

Bio: Jan Hardenbol is an academic researcher. The author has contributed to research in topics: Paleogene & Historical geology. The author has an hindex of 3, co-authored 4 publications receiving 1271 citations.

Geochronology, time scales and global stratigraphic correlation

Abstract: Geochronology, Time Scales, and Global Stratigraphic Correlation - The last decade has witnessed significant advances in analytic techniques and methodologic approaches to understanding earth history. This publication is a well-constructed geochronologic framework that allows estimation of rates of geologic processes, correlation of stratigraphies, and placement of discrete events in temporal order. Resulting from a research symposium at the 67th Annual SEPM meeting in New Orleans, Louisiana, April 1993, the 16 papers of this volume represent a broad spectrum of approaches to understanding earth history and the passage of geologic time.

A New Paleogene Numerical Time Scale

Abstract: New data and a reinterpretation of existing data are the bases for this emended Paleogene numerical time scale. Biostratigraphy, radiometric dating, stratotypes, and paleomagnetic stratigraphy have been independently evaluated and subsequently integrated into a single numerical time scale framework. In the three Paleogene series, Oligocene, Eocene, and Paleocene, we have recognized eight commonly used stages. The corresponding age-units vary in duration from 3 to 8 million years (average 5 Ma). As a result of the improvement in establishing the relationships between the stratotypes of these stages and plankton biostratigraphy, the position of the stages within the series has been modified from earlier integrated chronostratigraphic schemes. Stratotypes (type sections) represent the formal basis for relating rock and time. However, the stratotypes of the western European Paleogene stages were not originally established on the basis of planktonic microfossils, and it was therefore not possible to recognize these stages worldwide. Subsequently, independent plankton zonations were established that could not be properly related to the stratotypes of the standard European chronostratigraphic units. Nevertheless, tentative relationships between these planktonic zonations and the relative chronostratigraphic units have been suggested and have been followed for practical reasons by nearly all plankton biostratigraphers. Calcareous nannoplankton have recently provided an indirect means of relating the stratotypes of the northwestern European Paleogene stages to the planktonic foraminiferal biostratigraphy and have revealed discrepancies between these two stratigraphic systems. The most significant of these is in the Eocene, where the type section of the traditional late Eocene Bartonian contains planktonic microfossils generally considered indicative of middle Eocene age according to most biostratigraphers. This situation is corrected by placing the middle-late Eocene boundary between the Priabonian and the Bartonian. The alternative solution, moving planktonic foraminiferal zones P13 and P14 from middle to late Eocene, would cause far greater confusion in the worldwide correlation framework. An evaluation of published radiometric dates provided us with the following age ranges for the Paleogene geochronologic units: Oligocene: 24 to 37 Ma Late: 24 to 32 Ma (Chattian) Early: 32 to 37 Ma (Rupelian) End_Page 213------------------------ Eocene: 37 to 53.5 Ma Late: 37 to 40 Ma (Priabonian) Middle: 40 to 49 Ma (Bartonian 40-44 Ma) (Lutetian: 44-49 Ma) Early: 49 to 53.5 Ma (Ypresian Paleocene: 53.5 to 65 Ma Late: 53.5 to 60 Ma (Thanetian) Early: 60 to 65 Ma (Danian)

Revised Paleogene Polarity Time Scale

Abstract: A synthesis of radiometric data from continental volcaniclastics and volcanics that are tied to mammalian faunas reveals that an acceptance of recently revised age estimates on Eocene glauconites results in an offset in correlation between Eocene marine and continental stratigraphies by as much as an entire stage. A unified Eocene geochronology is maintained by retaining the earlier age estimates of the marine scale. The recent modification to the Paleogene part of the Cenozoic time-scale by Tarling and Mitchell (1976) is rejected.

Trends, Rhythms, and Aberrations in Global Climate 65 Ma to Present

Abstract: Since 65 million years ago (Ma), Earth's climate has undergone a significant and complex evolution, the finer details of which are now coming to light through investigations of deep-sea sediment cores. This evolution includes gradual trends of warming and cooling driven by tectonic processes on time scales of 10(5) to 10(7) years, rhythmic or periodic cycles driven by orbital processes with 10(4)- to 10(6)-year cyclicity, and rare rapid aberrant shifts and extreme climate transients with durations of 10(3) to 10(5) years. Here, recent progress in defining the evolution of global climate over the Cenozoic Era is reviewed. We focus primarily on the periodic and anomalous components of variability over the early portion of this era, as constrained by the latest generation of deep-sea isotope records. We also consider how this improved perspective has led to the recognition of previously unforeseen mechanisms for altering climate.

A revised Cenozoic geochronology and chronostratigraphy

Abstract: Since the publication of our previous time scale (Berggren and others, 1985c = BKFV85) a large amount of new magneto- and biostratigraphic data and radioisotopic ages have become available. An evaluation of some of the key magnetobiostratigraphic calibration points used in BKFV85, as suggested by high precision 40 Ar/ 39 Ar dating (e.g., Montanari and others, 1988; Swisher and Prothero, 1990; Prothero and Swisher, 1992; Prothero, 1994), has served as a catalyst for us in developing a revised Cenozoic time scale. For the Neogene Period, astrochron- ologic data (Shackleton and others, 1990; Hilgen, 1991) required re-evaluation of the calibration of the Pliocene and Pleistocene Epochs. The significantly older ages for the Pliocene-Pleistocene Epochs predicted by astronomical calibrations were soon corroborated by high precision 40 Ar/ 39 Ar dating (e.g., Baksi and others, 1992; McDougall and others, 1992; Tauxe and others, 1992; Walter and others, 1991; Renne and others, 1993). At the same time, a new and improved definition of the Late Cretaceous and Cenozoic polarity sequence was achieved based on a comprehensive evaluation of global sea-floor magnetic anomaly profiles (Cande and Kent, 1992). This, in turn, led to a revised Cenozoic geomagnetic polarity time scale (GPTS) based on standardization to a model of South Atlantic spreading history (Cande and Kent, 1992/1995 = CK92/95). This paper presents a revised (integrated magnetobiochronologic) Cenozoic time scale (IMBTS) based on an assessment and integration of data from several sources. Biostratigraphic events are correlated to the recently revised global polarity time scale (CK95). The construction of the new GPTS is outlined with emphasis on methodology and newly developed polarity history nomenclature. The radioisotopic calibration points (as well as other relevant data) used to constrain the GPTS are reviewed in their (bio)stratigraphic context. An updated magnetobiostratigraphic (re)assessment of about 150 pre-Pliocene planktonic foraminiferal datum events (including recently avail- able high southern (austral) latitude data) and a new/modified zonal biostratigraphy provides an essentially global biostratigraphic correlation framework. This is complemented by a (re)assessment of nearly 100 calcareous nannofossil datum events. Unrecognized unconformities in the stratigraphic record (and to a lesser extent differences in taxonomic concepts), rather than latitudinal diachrony, is shown to account for discrep- ancies in magnetobiostratigraphic correlations in many instances, particularly in the Paleogene Period. Claims of diachrony of low amplitude (<2 my) are poorly substantiated, at least in the Paleocene and Eocene Epochs. Finally, we (re)assess the current status of Cenozoic chronostratigraphy and present estimates of the chronology of lower (stage) and higher (system) level units. Although the numerical values of chronostratigraphic units (and their boundaries) have changed in the decade since the previous version of the Cenozoic time scale, the relative duration of these units has remained essentially the same. This is particularly true of the Paleogene Period, where the Paleocene/Eocene and Eocene/Oligocene boundaries have been shifted ~2 my younger and the Cretaceous/Paleogene boundary ~1 my younger. Changes in the Neogene time scale are relatively minor and reflect primarily improved magnetobiostratigraphic calibrations, better understanding of chronostratigraphic and magnetobiostratigraphic relationships, and the introduction of a congruent astronom- ical/paleomagnetic chronology for the past 6 my (and concomitant adjustments to magnetochron age estimates).

Global vegetation change through the Miocene/Pliocene boundary

Abstract: Between 8 and 6 million years ago, there was a global increase in the biomass of plants using C4 photosynthesis as indicated by changes in the carbon isotope ratios of fossil tooth enamel in Asia, Africa, North America and South America. This abrupt and widespread increase in C4 biomass may be related to a decrease in atmospheric CO2 concentrations below a threshold that favoured C3-photosynthesizing plants. The change occurred earlier at lower latitudes, as the threshold for C3 photosynthesis is higher at warmer temperatures.

Provenance of North American Phanerozoic sandstones in relation to tectonic setting

Abstract: Framework modes of terrigenous sandstones reflect derivation from various types of provenance terranes that depend upon plate-tectonic setting. Triangular QFL and QmFLt compositional diagrams for plotting point counts of sandstones can be subdivided into fields that are characteristic of sandstone suites derived from the different kinds of provenance terranes controlled by plate tectonics. Three main classes of provenance are termed “continental blocks,” “magmatic arcs,” and “recycled orogens.” Sandstone suites from each include three variants, of which the subfields lie within the larger subdivisions. Average modes for sandstone suites can be classified provisionally according to tectonic setting using the subdivided QFL and QmFLt plots. To test the validity of the classification, average modes for 233 Phanerozoic sandstone suites from North America were plotted on the triangular compositional diagrams and accompanying paleotectonic maps. Paired maps and ternary diagrams were prepared for eight different time slices, for each of which the tectonic setting of each major region within the continent remained relatively unchanged. Time slices are unequal in length but are controlled by the timing of major orogenic and rifting events that affected North America during the Phanerozoic. Comparison of the sandstone compositions with inferred tectonic setting through the Phanerozoic indicates that the proposed classification scheme is generally valid and yields satisfactory results when applied on a broad scale. Its application, together with other approaches, in regions of the world where over-all trends of geologic history are less well known could lead to important conclusions about the timing and nature of major tectonic events.