Chemostratigraphy versus biostratigraphy: data from around the Cenomanian–Turonian boundary

Abstract

A detailed isotopic profile is presented for a stratigraphically expanded Cenomanian–Turonian boundary section in Chalk facies exposed at Eastbourne, Sussex and compared with data from Pueblo, Colorado. In both sections macro- and micropalaeontological markers (first appearances and disappearances) are well-constrained, and their relative positions and relationship to the structure of the carbon-isotope curve are identical. This consistent relationship between two independent phenomena, one geochemical, the other biostratigraphical, is taken as evidence for the likely synchroneity of both the biostratigraphical markers and the carbon-isotope excursion in these two areas. This interpretation contrasts with suggestions made recently by other authors whose data have been taken to imply a lack of correlation between the carbon-isotope excursion in Europe and North America.

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

“…The isotope correlation between England and North America can be tested using last and first appearance datum levels (LAD, FAD) and floods of key fossil taxa in the reference sections. The relative positions of ammonite, inoceramid bivalve and planktonic foraminifera datum levels in the sections are consistent with the isotope correlation (Jarvis et al 1988b;Gale et al 1993Gale et al , 2005Paul et al 1999;Keller et al 2001Keller et al , 2004. fig.…”

“…The global nature of these events, particularly the large positive excursion spanning the Cenomanian/Turonian boundary, has been confirmed subsequently by many workers (e.g. Schlanger et al 1987;Arthur et al 1990;Gale et al 1993Gale et al , 2005Pratt et al 1993;Jenkyns, Gale & Corfield, 1994;Jenkyns, Mutterlose & Sliter, 1995;Hasegawa, 1997Hasegawa, , 2003Voigt & Hilbrecht, 1997;DeCabrera, Sliter & Jarvis, 1999;Hasegawa & Hatsugai, 2000;Voigt, 2000;Keller et al 2001;Wang et al 2001;Jarvis et al 2002;Tsikos et al 2004; Table 1). The isotope profile is shown in Figure 3.…”

“…1), affords the thickest Cenomanian/Turonian boundary section in the AngloParis Basin (Jefferies, 1962(Jefferies, , 1963Gale et al 1993Gale et al , 2005Paul et al 1999). The macrofossil (Mortimore, 1986;Gale et al 1993Gale et al , 2000Gale et al , 2005 and microfossil (Paul et al 1999;Keller et al 2001) biostratigraphy of the section has been documented in detail, and Paul et al (1999) have published high-resolution (5-10 cm sample spacing) δ 13 C and δ 18 O curves for a 24 m section incorporating the Cenomanian/Turonian boundary. Similar but lower resolution carbon-isotope curves were presented by Leary & Peryt (1991), Gale et al (1993), Jenkyns, Gale & Corfield (1994), Keller et al (2001) and Tsikos et al (2004).…”

“…Detailed studies of the Cenomanian/Turonian Boundary Event and the associated stable-isotope and biostratigraphy in England have been undertaken at Dover (Jarvis et al 1988b;Lamolda, Gorostidi & Paul, 1994) and Eastbourne (Leary & Peryt, 1991;Gale et al 1993Gale et al , 2005Paul et al 1999;Keller et al 2001;Tsikos et al 2004), and isotope curves have also been published for Speeton (Mitchell, Paul & Gale, 1996) and Culver (Jarvis, Murphy & Gale, 2001). The Eastbourne Gun Gardens section in West Sussex (Figs 1, 5) is the most expanded boundary section in chalk facies in NW Europe (Paul et al 1999), and is increasingly being used as an international reference for biostratigraphic and chemostratigraphic studies (Amédro, Accarie & Robaszynski, 2005;Erbacher et al 2005;Kolonic et al 2005;Kuhnt et al 2005).…”

The age of the Tojeira Formation (Late Jurassic, Early Kimmeridgian), of Montejunto, west-central Portugal

“…Carbon isotope chemostratigraphy is a reliable correlation tool when integrated with biostratigraphy (e.g., Gale et al 1993;Jarvis et al 2006;and many others). Reliability, which also may be called stratigraphic fidelity in marking specific levels, is dependent on multiple factors, however.…”