Stratigraphic (dis)continuity and temporal resolution of geological events in the upper Paleocene-lower Eocene deep sea record

Author(s): Aubry, Marie-Pierre
Author Affiliation(s): Primary:
Université de Montpellier II, Institut des Sciences de l'Evolution, Montpellier, France
Other:
New Mexico Museum of Natural History, United States
Woods Hole Oceanographic Institution, United States
Volume Title: Late Paleocene-early Eocene climatic and biotic events in the marine and terrestrial records
Volume Author(s): Aubry, Marie-Pierre, editor; Lucas, Spencer G.; Berggren, William A.
Source: Late Paleocene-early Eocene climatic and biotic events in the marine and terrestrial records, edited by Marie-Pierre Aubry, Spencer G. Lucas and William A. Berggren, p.37-66. Publisher: Columbia University Press, New York, NY, United States. ISBN: 0-231-10238-0
Note: In English. 69 refs.; illus., incl. 3 tables, strat. cols.
Summary: The rock record is the only support for reconstructing earth history. Although it is increasingly recognized that not all intervals of geological time are equally represented in sedimentary stratigraphic sections, it is commonly assumed that deep sea sections are essentially complete over long intervals (>10 my) of time. Consequently, stratigraphic records of isotopic and faunal changes are converted to temporal records mostly through linear interpolation/extrapolation using magnetic properties (reversals and susceptibility), sometimes complemented by characteristic isotopic signatures. With the help of theoretical cartoons I show how undeciphered unconformities in sections may blur the true patterns of temporal changes and how they affect temporal resolution in these sections. Temporal analysis of stratigraphic sections must be conducted to help distinguish between true events and pseudo-events. The latest Paleocene-earliest Eocene (Magnetic Chron C24r) interval is one of the poorest represented in the Cenozoic deep sea record. Yet, most studies have ignored this fact and have assumed temporal continuity of upper Paleocene-lower Eocene sections. Based on two examples I discuss errors that incur from inappropriate conversion of a stratigraphic sequence into a temporal (numerical) record. In the first example, I examine the consequences of a shortcoming of the current Geomagnetic Polarity Time Scale (GPTS), which stems from the use of an age calibration tie-point on a level in DSDP Site 550, which was assumed to correspond to a biochronal boundary but in fact dates the upper surface of an unconformity. In the second example, I revise the stratigraphic and temporal significance of a 5.5 m thick upper Paleocene-lower Eocene section recovered from DSDP Site 577 and show that paleoceanographic reconstructions and biodiversity changes that have been inferred from high-resolution isotopic records and diversity patterns are illusory due to temporal misinterpretation of the section and incorrect (temporal) correlation with other sections. The accuracy of geological interpretations is intimately dependent upon the correctness of the temporal interpretation of stratigraphic sections. For parts of the stratigraphic record that are riddled with unconformities, such as the upper Paleocene-lower Eocene interval, composite (virtual) reference sections provide the relative chronology of events and constitute the means of temporal correlations through stratigraphic analysis, not only of marine sections but also of sections in the continental record. Ultimately, the composite reference section assists in determining the best criterion(a)/event(s) to characterize epoch/series boundaries, and to select the most suitable Global Stratotype Section and Point (GSSP) to place the "golden spike."
Year of Publication: 1998
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Biodiversity; Biostratigraphy; Calibration; Cenozoic; Correlation; DSDP Site 550; DSDP Site 557; Deep Sea Drilling Project; Deep-sea environment; Eocene; Foraminifera; Geomagnetic Polarity Time Scale; IPOD; Invertebrata; Leg 80; Leg 82; Lower Eocene; Marine environment; Microfossils; North Pacific; Northwest Pacific; Ocean floors; Pacific Ocean; Paleocene; Paleocene-Eocene boundary; Paleogene; Protista; Sequence stratigraphy; Shatsky Rise; Stratigraphic boundary; Tertiary; Unconformities; Upper Paleocene; West Pacific
Coordinates: N483054 N483055 W0132622 W0132623
N384957 N384957 W0323335 W0323335
Record ID: 2000031855
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute.