Rau, Greg H; Arthur, Michael A; Dean, Walter E (1987): Nitrogen isotope ratios of Cretaceous Atlantic sedimentary sequences [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.714244, Supplement to: Rau, GH et al. (1987): 15N/14N variations in Cretaceous Atlantic sedimentary sequences: implication for past changes in marine nitrogen biogeochemistry. Earth and Planetary Science Letters, 82(3-4), 269-279, https://doi.org/10.1016/0012-821X(87)90201-9
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Abstract:
At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds (black shales) were found to have significantly lower delta15N values (lower 15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in particular have delta15N values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools. In contrast, black, organic-carbon-rich beds at a third site (DSDP Site 603) contain predominantly terrestrial organic matter and have C- and N-isotopic compositions similar to organic matter of modern terrestrial origin.
The recurring 15N depletion in the marine-derived Cretaceous sequences prove that the nitrogen they contain is the end result of an episodic and atypical biogeochemistry. Existing isotopic and other data indicate that the low 15N relative abundance is the consequence of pelagic rather than post-depositional processes. Reduced ocean circulation, increased denitrification, and, hence, reduced euphoric zone nitrate availability may have led to Cretaceous phytoplankton assemblages that were periodically dominated by N2-fixing blue-green algae, a possible source of this sediment 15N-depletion. Lack of parallel isotopic shifts in Cretaceous terrestrially-derived nitrogen (Site 603) argues that the above change in nitrogen cycling during this period did not extend beyond the marine environment.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 9.598100 * Median Longitude: -26.896633 * South-bound Latitude: -19.187700 * West-bound Longitude: -70.028500 * North-bound Latitude: 35.495200 * East-bound Longitude: 9.385800
Date/Time Start: 1975-03-03T00:00:00 * Date/Time End: 1983-05-05T00:00:00
Event(s):
41-367 * Latitude: 12.486800 * Longitude: -20.047200 * Date/Time: 1975-03-03T00:00:00 * Elevation: -4748.0 m * Penetration: 1153 m * Recovery: 173.6 m * Location: North Atlantic/BASIN * Campaign: Leg41 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 40 cores; 342 m cored; 0 m drilled; 50.8 % recovery
75-530A * Latitude: -19.187700 * Longitude: 9.385800 * Date/Time: 1980-07-29T00:00:00 * Elevation: -4629.0 m * Penetration: 1121 m * Recovery: 617.5 m * Location: South Atlantic/RIDGE * Campaign: Leg75 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 107 cores; 986.5 m cored; 9.5 m drilled; 62.6 % recovery
93-603B * Latitude: 35.495200 * Longitude: -70.028500 * Date/Time: 1983-05-05T00:00:00 * Elevation: -4633.0 m * Penetration: 1576.2 m * Recovery: 485.6 m * Campaign: Leg93 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 74 cores; 674.6 m cored; 0 m drilled; 72 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
3 datasets
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Datasets listed in this publication series
- Rau, GH; Arthur, MA; Dean, WE (1987): (Table 1) Lithology and N isotope ratios of DSDP Hole 41-367. https://doi.org/10.1594/PANGAEA.713963
- Rau, GH; Arthur, MA; Dean, WE (1987): (Table 1) Lithology, N isotope ratios and carbonate content of DSDP Hole 75-530A. https://doi.org/10.1594/PANGAEA.713964
- Rau, GH; Arthur, MA; Dean, WE (1987): (Table 1) Lithology, N isotope ratios and carbonate content of DSDP Hole 93-603B. https://doi.org/10.1594/PANGAEA.713965