|
Regular Article |
1 School of Earth Sciences & Geography, Centre for Earth and Environmental Science Research, Kingston University, Penrhyn Road, Kingston upon Thames KT1 2EE, UK (e-mail: i.jarvis{at}kingston.ac.uk)
2 School of Earth and Environmental Sciences, University of Greenwich, Chatham Maritime, Chatham, Kent ME4 4AW and Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
Scientific editing by John Howell.
The elemental (Si, Ti, Al, Mn, Ca, Zr) and carbon stable-isotope (
13C) geochemistry of a biostratigraphically well-constrained Cenomanian–Turonian (Upper Cretaceous) Chalk succession on the Isle of Wight, southern England, shows systematic variation that corresponds closely to a published sequence stratigraphic model for the Cenomanian. Six sequences and their constituent systems tracts, defined elsewhere using sedimentological criteria, are clearly distinguishable from bulk-sediment elemental profiles, and an additional Upper Cenomanian sequence previously identified in Spain is recognized in England from these geochemical data. The manganese curve is particularly instructive, exhibiting minima around sequence boundaries and through lowstands, rising values from the transgressive surfaces through transgressive systems tracts, maxima around maximum flooding surfaces, and declining values through highstands. Silica and trace-element (Ti, Zr) aluminium ratios peak around transgressive surfaces and maximum flooding surfaces, indicating pulses of increased siliciclastic input. Positive 13C excursions are confirmed at the base of the Middle Cenomanian and spanning the Cenomanian–Turonian boundary but are not evident in other sequences. Variation in Mn is related to bulk sedimentation rate and detrital versus biogenic supply, which control the Mn flux and the efficiency of the diagenetic Mn ‘pump’ that leads to elevated Mn contents in sediments. Manganese peaks do not generally correlate with positive 13C excursions, and although near-coincident Mn and 13C peaks occur around the Cenomanian–Turonian boundary, the former is not necessarily linked to the oceanic anoxic event occurring at that time. The global oceanic Mn flux may have been enhanced during the Cenomanian as a result of hydrothermal activity during rapid sea-floor spreading and oceanic plateau formation. Elemental chemostratigraphy provides a new tool for developing sequence stratigraphic models in pelagic and hemipelagic carbonate successions.
Keywords: chalk, 13C, sequence stratigraphy, manganese, chemostratigraphy.
This article has been cited by other articles:
 |
|
 |
|
  B.W. Lauridsen, A.S. Gale, and F. Surlyk Benthic macrofauna variations and community structure in Cenomanian cyclic chalk-marl from Southerham Grey Pit, SE England Journal of the Geological Society, 2009; 166: 115 - 127. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. JARVIS, A. S. GALE, H. C. JENKYNS, and M. A. PEARCE Secular variation in Late Cretaceous carbon isotopes: a new {delta}13C carbonate reference curve for the Cenomanian-Campanian (99.6-70.6 Ma) Geological Magazine, 2006; 143: 561 - 608. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. S. Gale, J. Hardenbol, B. Hathway, W. J. Kennedy, J. R. Young, and V. Phansalkar Global correlation of Cenomanian (Upper Cretaceous) sequences: Evidence for Milankovitch control on sea level Geology, 2002; 30: 291 - 294. [Abstract] [Full Text] [PDF]
|
|
