Lower Jurassic Stable Isotope and Chemical Data: Readme file
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               World Data Center for Paleoclimatology, Boulder
                                  and
                     NOAA Paleoclimatology Program
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NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!!


NAME OF DATA SET: Lower Jurassic Stable Isotope and Chemical Data 
LAST UPDATE: 1/2002 (Original Receipt by WDC Paleo)

CONTRIBUTOR: Hugh Jenkyns, Department of Earth Sciences,
University of Oxford

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2002-001

SUGGESTED DATA CITATION: 
Jenkyns, H.C., D.R. Gröcke, and S.P. Hesselbo, 2002,
Lower Jurassic Stable Isotope and Chemical Data, 
IGBP PAGES/World Data Center for Paleoclimatology 
Data Contribution Series # 2002-001.
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

ORIGINAL REFERENCE: 
Jenkyns, H.C., D.R. Gröcke, and S.P. Hesselbo, 2001, 
Nitrogen-isotope evidence for water mass denitrification 
during the Early Toarcian (Jurassic) Oceanic Anoxic Event,
Paleoceanography, 16, 593-603, December 2001

GEOGRAPHIC REGION: UK and Italy

PERIOD OF RECORD: Early Toarcian (Lower Jurassic) 

LIST OF FILES: Readme_jenkyns2001.txt (this file),
dogna.doc, hawsker_bottoms.doc, winterborne_kingston.doc, 
mochras.doc (Microsoft Word tables), 
dogna.txt, hawsker_bottoms.txt, winterborne_kingston.txt, 
mochras.txt (tab-delimited text files).

DESCRIPTION:
Jenkyns, Gröcke, and Hesselbo (2001) 
Lower Jurassic Stable Isotope and Chemical Data 

Carbon and nitrogen stable-isotope data and total organic carbon from 
UK (Hawsker Bottoms, Mochras Borehole, Winterborne Kingston Borehole)
and Italy (Dogna)

Abstract:  
Bulk sedimentary nitrogen-isotope (d15Ntot) data have been generated 
from Lower Jurassic black carbon-rich shales in the British Isles and 
northern Italy deposited during the Early Toarcian Oceanic Anoxic Event.
A pronounced positive d15Ntot excursion through the exaratum Subzone 
of the falciferum Zone (defined by characteristic ammonites in the 
British Isles) broadly correlates with a relative maximum in 
weight% total organic carbon (TOC) and, in some sections, with a 
negative d13Corg excursion.  Upwelling of a deoxygenated watermass 
that had under-gone partial denitrification is the likely explanation
for relative enrichment of d15Ntot, and parallels may be drawn with 
Quaternary sediments of the Arabian Sea, Gulf of California and 
northwest Mexican margin.  The development of Early Toarcian 
suboxic watermasses and consequent partial denitrification is attributed to
increases in organic productivity.  Approximately coincident phenomena 
include the following: a relative climatic optimum, realignment of 
major oceanic current systems and possible release of methane gas hydrates 
from continental-margin sediments early in the history of the 
oceanic anoxic event.