Stable carbon isotope development and sea-level changes during the Late Ludlow (Silurian) of the Łysogóry region (Rzepin section, Holy Cross Mountains, Poland)

Abstract

The Ludlow deposits of the Winnica Formation in the Rzepin section (Holy Cross Mountains, Poland) have been studied with respect to their facies evolution and stable carbon isotope ratios from whole-rock samples. The C-isotope curve of the Rzepin section records a distinct positive excursion with maximal values of ?8.9%. A Late Ludlow positive isotope excursion is known from different paleocontinents and thus is regarded as a global isotope event. The presence of the event allows for a chemostratigraphic correlation of the Rzepin profile with the classical, biostratigraphically well-dated Gotland section. The Ludlow deposits of the Holy Cross Mountains are interpreted in terms of sea-level changes during the isotope excursion. Because the Rzepin and Gotland sections are positioned on the opposite sides of the same foreland basin, a comparison of their sequence stratigraphy allows to test the regularities of the sea-level changes on the shelf of Baltica. In the present paper, a modified view of the recently published sequence stratigraphy of the Gotland succession is presented. Our results indicate that the positive Ludlow d 13 C excursion is connected with prolonged low-stand conditions with small, internal transgressive pulses.

Facies development and sequence stratigraphy of the Ludfordian (Upper Silurian) deposits in the Zbruch River Valley, Podolia, western Ukraine: local facies overprint on the δ13Ccarb record of a global stable carbon isotope excursion

“…Of potential utility for constraining the stratigraphic position of the interval investigated in the present study is the positive stable CIE recognized globally in the Ludfordian (Wenzel and Joachimski 1996;Bickert et al 1997;Kaljo et al 1997;Azmy et al 1998;Wigforss-Lange 1999;Wenzel et al 2000;Saltzman 2001;Calner 2005b;Martma et al 2005;Kaljo and Martma 2006;Jeppsson et al 2007;Kaljo et al 2007;Lehnert et al 2007;Eriksson and Calner 2008;Barrick et al 2010;Kozłowski and Munnecke 2010;Munnecke et al 2010;Cramer et al 2011;Loydell and Frýda 2011;Kaljo et al 2012;Kozłowski and Sobień 2012;Manda et al 2012). The beginning of the excursion coincides with an abrupt decrease in abundance of Polygnathoides siluricus, shortly before its Last Appearance Datum (LAD) (Martma et al 2005;Kaljo and Martma 2006;Jeppsson et al 2007;Lehnert et al 2007;Eriksson and Calner 2008).…”

“…These authors also introduced the ''top Ludfordian twin excursion'' based on the analysis of the Vidukle-61 and Ohesaare cores, where this smaller double peak is developed entirely within the O. crispa zone. This separate twin peak is, however, not visible in most sections, but elevated d 13 C values seem to decay at various rates (Kaljo et al 1997;Kaljo and Martma 2006;Kozłowski and Munnecke 2010;Kaljo et al 2012). According to Kaljo et al (2012), the Ludfordian excursion in Podolia is entirely contained within the Isakivtsy and Prygorodok Fms and the d 13 C carb values are close to 0 % in the Varnytsya Fm.…”

“…The beginning of the excursion coincides with an abrupt decrease in abundance of Polygnathoides siluricus, shortly before its Last Appearance Datum (LAD) (Martma et al 2005;Kaljo and Martma 2006;Jeppsson et al 2007;Lehnert et al 2007;Eriksson and Calner 2008). The peak interval is constrained within the O. snajdri zone (coeval with the top of the Neocucullograptus kozlowskii zone), and in many sections there is lithological evidence for a sub-stratigraphic (contained entirely within one biozone) gap or even erosion (Kaljo et al 1997;Calner 2005b;Lehnert et al 2007;Eriksson and Calner 2008;Kozłowski and Munnecke 2010;Loydell and Frýda 2011;Kaljo et al 2012;Kozłowski and Sobień 2012). The position of the falling limb of the excursion is less consistent.…”

“…Some local factors seem to have been involved in the record of the Lau excursion, which is mostly documented by d 13 C carb of limestones from the epicontinental basin developed during the early Paleozoic on Baltica. This Ludfordian CIE has been recorded in Sweden (?11.2 %, Wigforss-Lange 1999; ?8.80 %, Samtleben et al 2000), Lithuania (?8.2 %, Martma et al 2005), Latvia (?5 %, Kaljo and Martma 2006;Kaljo et al 2012), Poland (?8.9 %, Kozłowski and Munnecke 2010;?6.7 %, Kozłowski and Sobień 2012) and Ukraine (?6.9 %, Kaljo et al 2007; ?6.0 %, Kaljo et al 2012). These localities represent different settings across the carbonate platform and enable the detection of local variability in the CIE record and its dependence on local facies development.…”

“…The Ludfordian (Upper Silurian) stage was the time of the most pronounced positive stable carbon isotope excursion (CIE) in the Phanerozoic, known as the Lau excursion (Wenzel and Joachimski 1996;Bickert et al 1997;Wigforss-Lange 1999;Calner et al 2004;Martma et al 2005; Kaljo and Martma 2006;Jeppsson et al 2007;Kaljo et al 2007; Lehnert et al 2007;Eriksson and Calner 2008;Barrick et al 2010;Kozłowski and Munnecke 2010;Munnecke et al 2010;Cramer et al 2011;Loydell and Frýda 2011;Jeppsson et al 2012;Kaljo et al 2012;Kozłowski and Sobień 2012). Very good geochemical, biostratigraphical, and paleoecological documentation exists for the Lau excursion, and it is often used as a model to study positive CIEs, which are widely used as chemostratigraphic markers and as indicators of perturbations of the global carbon cycle (Jeppsson 1990;Aldridge et al 1993;Bickert et al 1997;Jeppsson and Aldridge 2000;Munnecke et al 2003;Calner 2005a;Melchin and Holmden 2006;Cramer and Saltzman 2007a, b;Fanton and Holmden 2007;Calner et al 2008;Małkowski et al 2009;Kozłowski and Sobień 2012).…”