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Cretaceous Chronostratagraphic Database

The CRETCSDB4, Cretaceous Chronostratigraphic Database, is a compilation of more than 3400 fossil taxa and marker beds calibrated to a numerical mega-annum scale (Fig. 1). These events are integrated from numerous published worldwide sections that span from the Jurassic/Cretaceous boundary to the Cretaceous/Paleogene boundary (Appendix 1). The numerical ages of the ranges have been interpolated by graphic correlation of the sections listed in Appendix 2. The ranges of first and last occurrences (FO/LO) are presented in mega-annums calibrated to standard Cretaceous stages defined by Global Stratotype and Section Points or to reference sections where GSSPs are not yet designated (Appendix 3). The ages of the taxa and marker beds are preliminary because ranges of some taxa are constrained by very few sections so that their ages may extend as new sections are added to the database. The ages of taxa that are common zonal indices are listed in Appendix 4; however the order of some events differs from published charts because reported occurrences may differ. The CRETCSDB4 ages of zonal Mollusca in the Western Interior compare closely with ages interpolated by Cobban et al. (2006, USGS Open-File Report 1250) (Appendix 5). The ages of rudists in CRETCSDB4 (Scott, 2010) are compared with ages interpolated with Strontium data (Steuber, 2001; Steuber et al., 1998, 2002, 2007).

This database may be used as a look-up table or as a point of reference for various quantitative methods of interpolation and calibration of other stratigraphic sections. Please note errors and discrepancies in an email to: Comments are welcome.

Figure 1 – CRET Time Scale 2014

Appendix 1Cretaceous Chronostratigraphic DATABASE: Preliminary File.  The age of Cen/Tur boundary revised to 93.00 Ma (within the error bar of 93.3±0.2 Ma (Obradovich, 1993, Geol. Assoc. Canada, Spec. Paper 39:379-396) and 93.06±0.25 Ma (Kowallis et al., 1995, Cret. Res., p. 127)
Appendix 2 – Section Catalog Files for Cretaceous Chronostratigraphic Database
Appendix 3 – Cretaceous stage type localities, criteria, and GSSPs in CRETCSDB Chronostratigraphic Database
Appendix 4 – Numerical Ages of Key Cretaceous Biostratigraphic Species in CRETCSDB
Appendix 5 – Numerical ages of Western Interior Ammonite and Inoceramid Zones.  Ages interpolated with radiometric ages by W. A. Cobban, J. D. Obradovich, I. Walaszcyk, and K. C. McKinney, 2006, USGS Open-File Report 2006-1250 on-line compared with ages interpolated from key published sections by graphic correlation.  Some ranges in CRETCSDB may be incomplete or absent because species are reported in too few published sections.
Appendix 6 – Numerical ages of select rudists. Strontium ages and 1998 ages from Steuber et al. 2007; Steuber et al. 1998; Steuber 2001; Steuber et al. 2002; and Fassett et al. 1997
Appendix 7 – Section Catalog Files for Cretaceous Chronostratigraphic Database: Projects MIDK3, MIDK4, MIDK41, MIDK42, MIDK45, LOK, CRET1, and CRET2

METHOD (from Scott, 2009)

“Graphic correlation is a quantitative, non-statistical, technique that determines the coeval relationships between two sections by comparing the ranges of event records in both sections (Shaw, 1964; Carney and Pierce, 1995). A graph of any pair of sections is an X/Y plot of the FOs (bases) and LOs (tops) of taxa found in both sections. The interpreter places a line of correlation (LOC) through the tops and bases that are at their maximum range in both sections. This LOC is the most constrained hypothesis of synchroneity between the two sections and alters the fewest bioevents. The LOC also accounts for hiatuses or faults at stratal discontinuities indicated by the lithostratigraphic record. The position of the LOC is defined by the equation for a regression line. Examples of the graphic technique are illustrated by Miller (1977) and Carney and Pierce (1995).

“The elements of a graph are the scaled X/Y axes, the fossil first occurrences-bases (FO; symbol) and the last occurrence-tops (LO; + symbol), and the line of correlation (LOC). The Y-axis is scaled in thickness of the measured section or well. The scale of the X-axis commonly is in thickness or relative units (Shaw, 1964; Carney and Pierce, 1995). In the process of compiling a chronostratigraphic database, the first section on the X-axis is the most complete record of deposition, called the standard reference section (SRS) (Carney and Pierce, 1995).

“This original method of graphic correlation compares the spacing of events in terms of thickness of the SRS (Shaw, 1964; Carney and Pierce, 1995; Gradstein et al., 2004a). A new method is to graph the SRS to a time scale so that the events are directly projected into numerical ages. The MIDK3 database was constructed in this way by graphing the Cenomanian-Turonian section at Kalaat Senan, Tunisia, to the 1989 time scale (Harland et al., 1990; Scott et al., 2000). The sedimentology, sequence stratigraphy, and biostratigraphy of this section were carefully documented and the section recorded continuous deposition at a uniform rate (Robaszynski et al. 1990, 1993). The stage boundaries were clearly and unequivocally defined biostratigraphically so that the LOC could be pinned to them. Thus all events were related to time. To further constrain the numeric ages of the database scale, sections with numerically dated beds were graphed and the X-axis scale was re-calibrated to millions of years (mega-annum, Ma) (Carney and Pierce, 1995; Scott et al., 2000).

“The X/Y plot compares the rate of sediment accumulation (RSA) in one section with that in the other (Miller, 1977). The RSA does not account for compaction or other processes that reduce the thickness of the interval from its initial depositional thickness, thus the sedimentation rate is not measured. The technique of graphic correlation enables the stratigrapher to consider sedimentologic events together with the biotic events and test conclusions based on sedimentology with those based on fossils. Also, the event beds may add to the precision and accuracy of the correlation.

“The new method of graphic correlation produces a comprehensive database that avoids the limitations of the method noted by Gradstein et al. (2004a). The ranges of more than 3000 bioevents and other markers in nearly 200 sections are calculated instantaneously and used in the interpretation of each subsequent section. If the analyst prefers to use average ranges, GraphCor has the capability to average the ranges, which is the data point used in Ranking and Scaling (RASC) (Gradstein et al., 2004a). Also like RASC method, graphic correlation plots all data points common to both the X and Y sections. Unlike RASC graphic correlation plots the maximum or average position of the data points on the X axis. “

The initial Cretaceous chronostratigraphic database began in 1994 using the then current numerical time scale (Harland et al., 1990), in which the age of the Cenomanian/Turonian boundary was calibrated at 90.5 Ma. Since then data has accumulated to re-calibrate this boundary at 93.5±0.8 Ma (Gradstein et al., 2004b). In order to re-calibrate the time scale of the Cretaceous Chronostratigraphic Database, the graph of the Pueblo section (MIDK.15) was reset so that boundary criteria moved back to 93.0 Ma. In all subsequent graphs of events across this boundary the FOs all shifte d older but the LOs did not. So a new section catalog was created, CRETFIX.CAT, composed of four sections: 1) CRET.1, which consists of key bioevents defining stage boundaries in the 2004 time scale; 2) NEWKAGES.1, which contains the stages and dated bentonites in the Gradsetin et al. (2004b) time scale; 3) CRETCS3.1, which is the composited list from the most recent project file, CRET2.CAT with the tops across the Cenomanian/Turonian boundary removed; and 4) MOWRY.1, which is the composite of all events in the Albian/Cenomanian Western Interior project. These sections were graphed and the LOCs saved resulting in the composite section, CRETCSDB.1. This list of taxa and events with calibrated ages can be used as the Standard Reference Section, SRS, for future projects of Cretaceous data sections.


Carney, J.L., and Pierce, R.W., 1995, Graphic correlation and composite standard databases as tools for the exploration biostratigrapher, in Mann, K.O., and Lane, H.R., eds., Graphic Correlation: SEPM (Society for Sedimentary Geology), Special Publication 53, p. 23-43.

Gradstein, F., Cooper, R.A., and Sadler, P.M., 2004a, Biostratigraphy: Time scale from graphic and quantitative methods, in Gradstein, F., Ogg, J., and Smith, A., eds., A geologic time scale 2004: Cambridge University Press, United Kingdom, p. 49-54.

Gradstein, F., Ogg, J., and Smith, A., 2004b, A geologic time scale 2004: Cambridge University Press, United Kingdom, 589 p.

Hardenbol, J., and Robaszynski, 1998, Introduction to the Upper Cretaceous, in de Graciansky, P.-C, Hardenbol, J., Jacquin, T., and Vail, P.R., eds., Mesozoic and Cenozoic sequence stratigraphy of European basins: SEPM (Society for Sedimentary Geology), Special Publication 54, p. 329-332.

Harland, W.B., Armstrong, R.L., Cox, A.V., Craig, L.E., Smith, A.G., and Smith, D.G., 1990, A geologic time scale 1989: Cambridge University Press, Cambridge, 263 p.

Hood, K.C., 1995, Evaluating the use of average composite sections and derived correlations in the graphic correlation technique, in Mann, K.O., and Lane, H.R., eds., Graphic Correlation: SEPM (Society for Sedimentary Geology), Special Publication 53, p. 83-93.

Miller, F.X. 1977. The graphic correlation method in biostratigraphy, in Kauffman, E.G., and Hazel, J.E., eds., Concepts and Methods of Biostratigraphy: Dowden, Hutchinson and Ross, Inc., Stroudsburg, Pa., p. 165-186.

Robaszynski, F., Caron, M., Dupuis, C., Amedro, F., Gonzalez Donoso, J.-M., Linares, D., Hardenbol, J., Gartner, S., Calandra, F., and Deloffre, R., 1990. A tentative integrated stratigraphy in the Turonian of central Tunisia: Formations, zones and sequential stratigraphy in the Kalaat Senan area. Bulletin Centres Recherches Exploration Production Elf-Aquitaine, v. 14, p. 213-384.

Robaszynski, F., Caron, M., Amédro, F., Dupuis, C., Hardenbol, J., Gonzalez Donoso, J.M., Linares, D., and Gartner, S., 1993. Le Cénomanien de la région de Kalaat Senan (Tunisie centrale): Litho-biostratigraphie et interprétation séquentielle. Revue de Paléobiologie, v. 12, p. 351–505.

Scott, R.W. 2009. Chronostratigraphic Database for Upper Cretaceous Oceanic Red Beds (CORBs). In: Hu, X. Wang, C., Scott, R., Wagreich, M., & Jansa, L. (eds). Cretaceous Oceanic Redbeds: Stratigraphy, Composition, Origins, Paleogeographic, and Paleoclimatic significance: SEPM (Society for Sedimentary Geology), Special Publication 91, p. 31-53.

Scott, R.W., W. Schlager, B. Fouke, and S.A. Nederbragt, 2000, Are Mid-Cretaceous eustatic events recorded in Middle East carbonate platforms?, in Alsharhan, A.S., and Scott, R.W., eds., Middle East Models of Jurassic/Cretaceous Carbonate Systems: SEPM Special Publication 69, p. 77-88.

Shaw, A.B., 1964, Time in Stratigraphy: McGraw-Hill, New York, 365 p.

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