The magnetostratigraphy of Coniacian-Late Campanian chalk sequences in southern England

Montgomery, Paul; Hailwood, E. A.; Gale, Andy; Burnett, J. A.

doi:10.1016/s0012-821x(98)00008-9

Cited by 63 publications

(29 citation statements)

References 34 publications

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“…14). In England, the Chron 34n/33r boundary occurs a short distance above the base of the Upper Santonian in the lower Uintacrinus Zone Montgomery et al 1998), consistent with its position in Russia (Pechersky, Naidin & Molotovsky, 1983). In Italy, the reversal has generally been regarded as occurring immediately above the base of the Campanian Alvarez & Lowrie, 1978;Cresta, Monechi & Parisi, 1989;Premoli Silva & Sliter, 1995).…”

Section: A Boreal-tethyan Carbon-isotope Correlationmentioning

confidence: 84%

“…Gubbio biostratigraphy after Premoli Silva & Sliter (1995), derived from the Bottaccione section. The position of the base of Chron 33r (dashed horizontal line) is indicated Montgomery et al 1998), marking the termination of the Cretaceous Long Normal (Chron 34n). The Bottaccione δ 13 C data display a systematic offset of around + 0.1 ‰ compared to the Contessa Quarry and English Chalk data.…”

Section: A Eustatic Sea-levelmentioning

confidence: 99%

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

et al. 2006

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-Carbon stable-isotope variation through the Cenomanian-Santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven Chalk successions in England. The sections show consistent stratigraphic trends and δ 13 C values that provide a basis for highresolution correlation. Positive and negative δ 13 C excursions and inflection points on the isotope profiles are used to define 72 isotope events. Key markers are provided by positive δ 13 C excursions of up to + 2 ‰: the Albian/Cenomanian Boundary Event; Mid-Cenomanian Event I; the Cenomanian/Turonian Boundary Event; the Bridgewick, Hitch Wood and Navigation events of Late Turonian age; and the Santonian/Campanian Boundary Event. Isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons. An age-calibrated composite δ 13 C reference curve and an isotope event stratigraphy are constructed using data from the English Chalk. The isotope stratigraphy is applied to successions in Germany, France, Spain and Italy. Correlation with pelagic sections at Gubbio, central Italy, demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the Cenomanian-Turonian stages, confirming established relationships between Tethyan planktonic foraminiferal and Boreal macrofossil biozonations. Correlation of the Coniacian-Santonian stages is less clear cut: magnetostratigraphic evidence for placing the base of Chron 33r near the base of the Upper Santonian is in good agreement with the carbon-isotope correlation, but generates significant anomalies regarding the placement of the Santonian and Campanian stage boundaries with respect to Tethyan planktonic foraminiferal and nannofossil zones. Isotope stratigraphy offers a more reliable criterion for detailed correlation of Cenomanian-Santonian strata than biostratigraphy. With the addition of Campanian δ 13 C data from one of the English sections, a composite Cenomanian-Campanian age-calibrated reference curve is presented that can be utilized in future chemostratigraphic studies.The Cenomanian-Campanian carbon-isotope curve is remarkably similar in shape to supposedly eustatic sea-level curves: increasing δ 13 C values accompanying sea-level rise associated with transgression, and falling δ 13 C values characterizing sea-level fall and regression. The correlation between carbon isotopes and sea-level is explained by variations in epicontinental sea area affecting organic-matter burial fluxes: increasing shallow sea-floor area and increased accommodation space accompanying sea-level rise allowed more efficient burial of marine organic matter, with the preferential removal of 12 C from the marine carbon reservoir. During sea-level fall, reduced seafloor area, marine erosion of previously deposited sediments, and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter, causing falling δ 13 C values. Additionally, drowning of carbonate platforms during...

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Section: A Boreal-tethyan Carbon-isotope Correlationmentioning

confidence: 84%

Section: A Eustatic Sea-levelmentioning

confidence: 99%

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

et al. 2006

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“…As an example application of this scoring system, consider the magnetofossils from the Cretaceous chalk deposits of southern England (Table 2 and Figure 6, c-d) (Hounslow and Maher, 1996;Maher et al, 1999;Montgomery et al, 1998). These magnetofossils were identified in the course of a broad paleomagnetic study that yielded robust results, with a paleomagnetic quality index of 5.…”

Section: Example Magnetofossil Scoresmentioning

confidence: 99%

“…The oldest robust magnetofossils yet found come from Cretaceous (ConiacianCampanian) chalk deposits of southern England (Hounslow and Maher, 1996;Maher et al, 1999;Montgomery et al, 1998). These sediments have been the subject of paleomagnetic, rock magnetic, SEM, and TEM studies.…”

Section: Phanerozoic Magnetofossilsmentioning

confidence: 99%

The identification and biogeochemical interpretation of fossil magnetotactic bacteria

Kopp

Kirschvink

2008

Earth-Science Reviews

315

349

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Magnetotactic bacteria, which most commonly live within the oxic-anoxic transition zone (OATZ) of aquatic environments, produce intracellular crystals of magnetic minerals, specifically magnetite or greigite. The crystals cause the bacteria to orient themselves passively with respect to the geomagnetic field and thereby facilitate the bacteria's search for optimal conditions within the sharp chemical gradients of the OATZ. The bacteria may also gain energy from the redox cycling of their crystals.Because magnetotactic bacteria benefit from their magnetic moments, natural selection has promoted the development of traits that increase the efficiency with which the intracellular crystals impart magnetic moments to cells.These traits also allow crystals produced by magnetotactic bacteria (called magnetofossils when preserved in sediments) to be distinguished from abiogenic particles and particles produced as extracellular byproducts of bacterial metabolism. Magnetofossils are recognizable based on their narrow size and shape distributions, distinctive morphologies with blunt crystal edges, chain arrangement, chemical purity, and crystallographic perfection. This article presents a scheme for rating magnetofossil robustness based on these traits.The magnetofossil record extends robustly to the Cretaceous and with lesser certainty to the late Archean. Because magnetotactic bacteria predominantly live in the OATZ, the abundance and character of their fossils can reflect environmental changes that alter the chemical stratification of sediments and the water column. The magnetofossil record therefore provides an underutilized archive of paleoenvironmental information. Several studies have demonstrated a relationship between magnetofossil abundance and glacial/interglacial cycles, likely mediated by changes in pore water oxygen levels. More speculatively, a better-developed magnetofossil record might provide constraints on the long-term evolution of marine redox stratification. More work in modern and ancient settings is necessary to explicate the mechanisms linking the abundance and character of magnetofossils to ancient biogeochemistry.

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“…Grant (1998) provides a sequence stratigraphy of the Culver Down / Whitecliff Chalk succession that can be correlated with the Scratchell"s Bay succession. Montgomery (1994) and Montgomery et al (1998) compare the magneto-stratigraphy of Scratchell"s Bay and Culver Down. Hart et al (1989) published a small-scale outline section for both Alum Bay (Upper Campanian) and Scratchell"s Bay (Santonian to late Campanian only) but this appears to be a further presentation of the section utilised by Swiecicki (1980 A complete manuscript lithological log from the Palaeogene unconformity in Alum Bay around the Needles promontory and into Scratchell"s Bay was kindly provided by Professor Andy Gale (pers.…”

Section: Introductionmentioning

confidence: 99%

The lithostratigraphy and biostratigraphy of the Chalk Group (Upper Coniacian to Upper Campanian) at Scratchell's Bay and Alum Bay, Isle of Wight, UK

Hopson

Farrant

Wilkinson

et al. 2011

Proceedings of the Geologists' Association

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The Scratchell"s Bay and southern Alum Bay sections, in the extreme west of the Isle of Wight on the Needles promontory, cover the stratigraphically highest Chalk Group formations available in southern England. They are relatively inaccessible, other than by boat, and despite being a virtually unbroken succession they have not received the attention afforded to the Whitecliff GCR (Geological Conservation Review series) site at the eastern extremity of the island. A detailed account of the lithostratigraphy of the strata in Scratchell"s Bay is presented and integrated with macro and micro biostratigraphical results for each formation present. Comparisons are made with earlier work to provide a comprehensive description of the Seaford Chalk, Newhaven Chalk, Culver Chalk and Portsdown Chalk formations for the Needles promontory.The strata described are correlated with those seen in the Culver Down CliffsWhitecliff Bay at the eastern end of the island that form the Whitecliff GCR site. This provides an overall correlation for the Upper Coniacian to Upper Campanian Chalk strata on the island.The influence of the Purbeck -Wight structure (Sandown and Brighstone periclines) on the Chalk Group strata is discussed and the conclusions drawn demonstrate that movement on this structure is diachronous across the island.

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The magnetostratigraphy of Coniacian-Late Campanian chalk sequences in southern England

Cited by 63 publications

References 34 publications

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

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

The identification and biogeochemical interpretation of fossil magnetotactic bacteria

The lithostratigraphy and biostratigraphy of the Chalk Group (Upper Coniacian to Upper Campanian) at Scratchell's Bay and Alum Bay, Isle of Wight, UK

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The magnetostratigraphy of Coniacian-Late Campanian chalk sequences in southern England

Cited by 63 publications

References 34 publications

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

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

The identification and biogeochemical interpretation of fossil magnetotactic bacteria

The lithostratigraphy and biostratigraphy of the Chalk Group (Upper Coniacian to Upper Campanian) at Scratchell's Bay and Alum Bay, Isle of Wight, UK

Contact Info

Product

Resources

About

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

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