Compilation of Total Organic and Inorganic Carbon Data from Peru Margin and Eastern Equatorial Pacific Drill Sites (Odp Legs 112, 138, and 201)1

Compilation of Total Organic and Inorganic Carbon Data from Peru Margin and Eastern Equatorial Pacific Drill Sites (Odp Legs 112, 138, and 201)1

Jørgensen, B.B., D’Hondt, S.L., and Miller, D.J. (Eds.) Proceedings of the Ocean Drilling Program, Scientific Results Volume 201 8. DATA REPORT: COMPILATION OF TOTAL ORGANIC AND INORGANIC CARBON DATA FROM PERU MARGIN AND EASTERN EQUATORIAL PACIFIC DRILL SITES (ODP LEGS 112, 138, AND 201)1 P. M e is t er, 2 M. Prokopenko,3 C.G. Skilbeck,3 M. Watson,3 F1. Map of Peru margin and the and J.A. McKenzie2 eastern equatorial Pacific, p. 7. 5 S Site 1225/851 Galapagos Site Islands 1227/684 Site Trujillo Basin 1226/846 Peru Site 1230/685 Salaverry Basin margin 10 P Site 1229/681 e r L i m u T r e a B a n c h Site 1228/680 Site 1231/321 s i n P B is a c s o Peru Basin in N km 15 0 200 400 85W 80 75 INTRODUCTION 1Meister, P., Prokopenko, M., Skilbeck, Organic matter deposited and buried under the seafloor is one of the C.G., Watson, M., and McKenzie, J.A., major carbon sources for microbial life in the deep subsurface of the 2005. Data report: Compilation of ocean. In this report, we present a compilation of all available total or- total organic and inorganic carbon ganic carbon (TOC) and total inorganic carbon (TIC) data for the sites data from Peru margin and eastern equatorial Pacific drill sites (ODP Legs drilled during Ocean Drilling Program (ODP) Leg 201. We include the 112, 138, and 201). In Jørgensen, B.B., TOC and TIC data from sites of Deep Sea Drilling (DSDP) Leg 34 and D’Hondt, S.L., and Miller, D.J. (Eds.), ODP Legs 112 and 138 (Yeats, Hart, et al., 1976; Suess, von Huene, et al., Proc. ODP, Sci. Results, 201, 1–20 1988; Mayer, Pisias, Janecek, et al., 1992), which were reoccupied dur- [Online]. Available from World Wide ing ODP Leg 201. Additional data from Leg 201 shore-based analyses Web: <http://www-odp.tamu.edu/ publications/201_SR/VOLUME/ are also included in the compilation. CHAPTERS/105.PDF>. [Cited YYYY- MM-DD] 2Geological Institute, ETH, STUDIED SITES 8092 Zurich, Switzerland. Correspondence author: Reoccupied Leg 201 drill sites are located in different contrasting geo- patrick.meister@alumni.ethz.ch 3Geological Institute, ETH Zurich, logical settings (Fig. F1). Sites 1225/851 and 1226/846 are located in the Sonneggstrasse 5, 8092 Zurich, eastern equatorial Pacific. They show an open-ocean stratigraphic se- Switzerland. quence dominated by nannofossil and diatom ooze of the high-produc- tivity south equatorial boundary current (Mayer, Pisias, Janecek, et al., Initial receipt: 8 July 2004 1992). In contrast, sediments of the Peru margin shelf sites (Sites 1227, Acceptance: 12 November 2004 Web publication: 12 July 2005 1228, and 1229) show variable contents of siliciclastic material and low Ms 201SR-105 P. MEISTER ET AL. DATA REPORT: TOTAL ORGANIC AND INORGANIC CARBON DATA 2 contents of carbonaceous nannoplankton (Suess, von Huene, et al., 1988). Strong coastal upwelling increases productivity at these sites, and most of these sediments are deposited at low oxygen content. Sedi- ments of the Peru Trench (Site 1230) also show upwelling-related sedi- mentation with mainly diatom ooze and variable siliciclastic content (Suess, von Huene, et al., 1988). At this site, methanogenic activity is enhanced and gas hydrates were found (D’Hondt, Jørgensen, Miller, et al., 2003). Site 1231 is located in the Peru Basin, far away from high or- ganic matter input, showing low productivity with mixed pelagic sedi- mentation (Yeats, Hart, et al., 1976). METHODS Total organic and inorganic carbon were measured onboard the drill ship and in shore-based laboratories using six different methods. Ship- board coulometry was used for analysis of total carbon (TC) and TIC during Leg 112. For analytical procedures, we refer to the “Explanatory Notes” chapter in the Leg 112 Initial Reports volume (Shipboard Scien- tific Party, 1988) and Emeis et al. (1990). During Legs 138 and 201, a carbon-nitrogen-sulfur elemental analyzer was available for TC mea- surements (Mayer, Pisias, Janecek, et al., 1992; D’Hondt, Jørgensen, Miller, et al., 2003). Additional TOC data are available from Rock-Eval pyrolysis, from both shipboard (Suess, von Huene, et al., 1988; Mayer, Pisias, Janecek, et al., 1992; D’Hondt, Jørgensen, Miller, et al., 2003) and Leg 112 shore- based measurements (Emeis et al., 1990; Emeis and Morse, 1990). A high-resolution profile of carbonate and organic carbon for Leg 112 Site 680 was analyzed on shore by Wefer et al. (1990) using the method of Weliky et al. (1983). Using a combined wet-oxidation acidifi- cation method, carbonate and organic carbon were discriminated and CO2 was analyzed using a thermal conductivity detector. During Leg 201 shore-based investigation, samples from Sites 1227, 1229, and 1230 were analyzed for δ13C of TC and weight percent of TC at University of Southern California (Los Angeles, USA) using an Iso- prime GV Instruments mass spectrometer interfaced with Carlo Erba 2500 NC elemental analyzer in the continuous flow mode. Precision (2σ) for daily runs for δ13C is ± 0.1‰ or better, based on internal stan- dards. Precision for TC (weight percent) is 0.1 wt% or better (based on duplicate runs on different days). Weight percent TOC is reported based on the isotopic mass balance, where it was assumed that δ13C of TOC is –21‰ and δ13C TIC is 0‰. Mass balance calculations using δ13C values of –20‰ or –22‰ for organic matter produced variations of estimated TOC content of ±0.15 wt%. Compared to the high varia- tions of ±5 to 10 wt% measured at the Peru margin shelf sites, a possi- ble contribution of terrestrial organic matter would only slightly affect TOC values (< ±1 wt%) calculated by this method. High-resolution profiles of total organic matter (TOM) in the upper- most 5–10 meters below seafloor (mbsf) at the Peru margin sites were also measured during Leg 201 shore-based investigation at the Depart- ment of Environmental Sciences (University of Technology at Sydney, Australia), using the method of Dean (1974). Between 0.4 and 1.2 g of dried sediment was combusted for 1 hr at 550°C in a Moloney furnace. The difference in weight at room temperature before and after the com- bustion (TOM in weight percent) was converted to TOC using the for- mula of Redfield et al. (1963) for the average composition of marine P. MEISTER ET AL. DATA REPORT: TOTAL ORGANIC AND INORGANIC CARBON DATA 3 organic matter. As mixing with terrestrial organic matter would increase the carbon concentration of the organic matter, using the Redfield ratio F2. Compiled TOC and TIC, Site gives minimum values for the TOC. But in any case, a contribution of 1225/851, p. 8. TOC (wt%) TIC (wt%) terrestrial material at the Peru margin sites, would not strongly affect Age Lithology 0 0.1 0.2 0.3 0.4 0 5 10 15 TOC compared to the high variations observed at these sites. For mea- Pleist. 50 surement of inorganic carbon, the residual TOM sample was combusted Pliocene for an additional hour at 1000°C. 100 A few samples from Legs 201 and 112 (including the dolomitic sam- 150 ples; 10 mg each) were analyzed on shore using a UIC, Inc. coulometer Depth (mbsf) 200 system at the Geological Institute, ETH Zurich (Switzerland). Miocene 250 300 Diatom ooze Leg 138 shipboard CNS analysis RESULTS AND DISCUSSION Radiolarian ooze Leg 138 shipboard coulometry Leg 201 shipboard coulometry Nannofossil ooze Foraminifer ooze Although the samples were measured using different methods, the overall patterns and the range of values were reproducible (Figs. F2, F3, F3. Compiled TOC and TIC, Site F4, F5, F6, F7, F8, F9; Tables T1, T2, T3, T4, T5; only new data are listed 1226/846, p. 9. TOC (wt%) TIC (wt%) Age Lithology 0 1 2 3 0 5 10 15 20 in the tables). Dolomitic samples typically show a much lower TOC 0 Pleist. content and do not follow the general trends (Tables T2, T3, T4, T5; not 50 50 100 100 late shown in the figures). Pliocene 150 150 early 20 Pliocene 200 200 200 Eastern Equatorial Pacific (Sites 1225/851 Depth (mbsf) 250 late Miocene and 1226/846) 300 300 300 350 middle TIC values measured from the eastern equatorial Pacific Sites 1225/ Miocene 400 e. Mio. 851 and 1226/846 vary in major part between 6 and 10 wt%, reflecting Diatom ooze Leg 138 shipboard CNS analysis Nannofossil ooze Leg 138 shipboard coulometry Leg 201 shipboard CNS analysis Nannofossil chalk Leg 201 shipboard coulometry Carbonate layer the high content of calcareous nannoplankton (Mayer, Pisias, Janecek, Leg 201 shore-based coulometry Quartz layer Leg 201 shore-based coulometry et al., 1992) (Figs. F2, F3; Table T1). In contrast, the late Miocene car- (diagenetic carbonates) bonate crisis is well documented by a low TIC content in the diatom- rich zone between 200 and 300 mbsf at Site 1225/851 and at 262.7 and F4. Compiled TOC and TIC, Site 317 mbsf at Site 1226/846 (Mayer, Pisias, Janecek, et al., 1992). At Site 1227/684, p. 10. TOC (wt%) TIC (wt%) 10 1226/846, the TIC content is also relatively depleted in upper Pliocene Age Lithology 051005 Pleist. (50–70 mbsf) and upper Pleistocene sediments (uppermost 10 mbsf). TOC at Site 1225/851 varies between 0 and 0.4 wt% throughout the Pliocene profile (Fig. F2), whereas at Site 1226/846, the TOC value reaches 1–2 50 wt% in the diatomaceous zones (Fig. F3; Table T1). The TOC-rich zone at Site 1226/846 between 270 and 315 mbsf correlates with the peak Depth (mbsf) 100 Mn concentration and probably reflects high Mn-reducing microbial Miocene activity (D’Hondt, Jørgensen, Miller, et al., 2003).

View Full Text

Details

  • File Type
    pdf
  • Upload Time
    -
  • Content Languages
    English
  • Upload User
    Anonymous/Not logged-in
  • File Pages
    20 Page
  • File Size
    -

Download

Channel Download Status
Express Download Enable

Copyright

We respect the copyrights and intellectual property rights of all users. All uploaded documents are either original works of the uploader or authorized works of the rightful owners.

  • Not to be reproduced or distributed without explicit permission.
  • Not used for commercial purposes outside of approved use cases.
  • Not used to infringe on the rights of the original creators.
  • If you believe any content infringes your copyright, please contact us immediately.

Support

For help with questions, suggestions, or problems, please contact us