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Geology; March 2008; v. 36; no. 3; p. 203-206; DOI: 10.1130/G24523A.1
© 2008 Geological Society of America
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Rapid warming and salinity changes of Cretaceous surface waters in the subtropical North Atlantic

Thomas Wagner1, Jens O. Herrle2, Jaap S. Sinninghe Damsté3, Stefan Schouten3, Isabel Stüsser4 and Peter Hofmann4

1 School of Civil Engineering and Geosciences, Newcastle University, Devonshire Building, Newcastle upon Tyne NE1 7RU, UK
2 Department of Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
3 Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Texel, Netherlands
4 Institute for Geology and Mineralogy, University of Cologne, Zülpicher Strasse 49a, 50674 Köln, Germany


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES CITED
 
Paleomarine carbon isotopic records reveal occasional and rapid release of greenhouse gases into the atmosphere. The regional consequences on surface ocean properties and time relationships between the atmosphere and the ocean, however, are still far from understood. We observe a sudden -1.5{per thousand} shift in leaf wax n-alkane 13C values at the onset of oceanic anoxic event (OAE) 1b from early Albian sediments off northwest Africa (Deep Sea Drilling Project Site 545) that is best explained by the rapid release of isotopically light carbon into the Cretaceous atmosphere. This -1.5{per thousand} shift in the n-alkanes precedes a negative isotope excursion of similar magnitude observed in marine carbonate, organic matter, and algal steranes. A TEX86-based record of sea surface temperature (SST) confirms almost instantaneous warming by ~3.5 °C along with the marine isotope shifts at Site 545, paralleled by an ~2 °C TEX86-SST increase and a freshening of surface water salinity from 43 to 41 at Blake Nose, Ocean Drilling Program Site 1049. Multiproxy evidence indicates that, once established, these warm SSTs prevailed and were stable during OAE 1b, suggesting that the emission of 13C-depleted carbon started abruptly but then continued over tens of thousands of years. The SST cooled by ~1–2 °C at the end of the event, not reaching pre-excursion levels. The new records provide evidence for a time lag (best estimate ~1–3 k.y.) between atmospheric and oceanic processes that we interpret as a direct response to changes in the atmospheric greenhouse gas concentrations followed by propagation into the ocean and subsequent heating of surface waters.

Key Words: oceanic anoxic events • sea surface temperature • biomarkers • atmosphere-ocean interactions • biogeochemical cycling


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES CITED
 
Mesozoic oceanic anoxic events (OAEs) represent an extremely perturbed mode of the atmosphere-ocean system often associated with greenhouse conditions and extremely warm surface waters. They document extraordinary, relatively short lived (i.e., 50–1500 k.y.) intervals when major perturbations in the global carbon budget were accompanied by massive burial of marine organic carbon (OC; see review by Jenkyns, 2003). At least two of them, the Toarcian OAE and the early Aptian OAE 1a, show a rapid negative carbon isotope excursion in sedimentary carbon at the onset of the event (e.g., Jenkyns, 2003). In analogy to the mechanism proposed for the Paleocene-Eocene Thermal Maximum (PETM; Dickens et al., 1995), these Mesozoic excursions have also been attributed to massive release of methane, although other mechanisms have been debated (e.g., Jenkyns, 2003).

To address the issue of climate perturbation and ocean response during Cretaceous OAEs we focus on the short (~45 k.y.) early Albian Paquier event (OAE 1b sensu stricto). The OAE 1b interval represents a major transition in Cretaceous tectonics, sea level, climate, lithofacies, and marine plankton communities, and also contains several prominent black shales (see Leckie et al., 2002, for review). OAE 1b is characterized by a distinct negative shift in various carbon reservoirs (Wagner et al., 2007) and high contributions of organic matter of non-thermophilic, marine archaeal origin in the subtropical and temperate ocean (Kuypers et al., 2001; Tsikos et al., 2004). Also documented is a distinct increase in sea-surface temperature (SST) and perturbations in the hydrological balance (Erbacher et al., 2001; Herrle et al., 2003). The causes and feedbacks of the OAE 1b carbon perturbation are still debated. Recent model simulations for Site 545 (Wagner et al., 2007) suggest an almost instantaneous average global warming of 0.3 °C at the onset of OAE 1b followed by ~0.8 °C cooling for the remainder of the event, relative to pre-OAE levels. The match between simulations and stratigraphic data at Site 545 (Wagner et al., 2007) was interpreted to support earlier studies (Jenkyns, 2003) that proposed that enhanced methane emission triggered OAE 1b.

Here we report biomarker data from the Mazagan Plateau (Deep Sea Drilling Project, DSDP, Site 545) and Blake Nose Plateau (Ocean Drilling Program, ODP, Site 1049; Fig. 1) to provide constraints on the magnitude and timing of the isotopic excursion and on SSTs and surface water salinity (SSS) stability during OAE 1b.


Figure 01
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  		Figure 1. Locations of Atlantic and Vocontian Basin oceanic anoxic event (OAE) 1b sites superimposed on the paleogeographic map of the mid-Cretaceous, ca. 110 Ma (from Wagner et al., 2007). A: Biostratigraphy, lithology, and sedimentary structures across studied section (389.5–391.0 m below seafloor), including the OAE 1b black shale unit at Deep Sea Drilling Project (DSDP; ODP—Ocean Drilling Program) Site 545 (Shipboard Scientific Party, 1984). Core photo shows gradational contact at base of the black shale. B: Bulk carbonate stable carbon isotopic ({delta}13 Ccarb) records (vs. Peedee belemnite, PDB) covering OAE 1b (light gray shading) at three different locations.

 

   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES CITED
 
Sample material for this study was obtained from the lower part of the Hedbergella planispira foraminiferal zone at centimeter-scale resolution from DSDP Site 545 sections 1–4 of core 42 (388.5–394.5 m below seafloor, mbsf). The studied interval at Mazagan Plateau is characterized by undisturbed weakly bio-turbated to laminated nannofossil-rich clay-stone above and below the OAE 1b black shale (Fig. 1A). The Paquier black shale (marked by the gray shaded bands in Figs. 1B, 2, and 3) is composed of laminated nannofossil claystone. A detailed study shows a gradational contact of the black shale and the nannofossil-rich clay-stone (our observations and Shipboard Scientific Party, 1984; see Fig. 1A). Hard grounds, interruptions, or sedimentary gaps across the studied interval are not observed (Fig. 1A). Samples from ODP Site 1049 were described in Kuypers et al. (2001). All TEX86 data were newly generated using improved analytical methods (cf. Schouten et al., 2007a). Procedures for organic geochemical and isotopic analyses are provided in the GSA Data Repository.1


Figure 02
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  		Figure 2. Geochemical records of oceanic anoxic event (OAE) 1b sediments from Deep Sea Drilling Project (DSDP) Site 545 (see Fig. 1A): stable carbon isotopes of bulk carbonate ({delta}13 Ccarb) and organic carbon (OC) ({delta}13 Corg), content of total OC (TOC) and carbonate (CaCO3), compound-specific stable carbon isotope data from marine C27-sterenes and averaged terrestrial long-chain C27, C29, C31 n-alkanes, and TEX86-based estimates of sea surface temperature (SST). TEX86-SST data are presented for Ocean Drilling Program (ODP) Site 1049 at Blake Nose. Stratigraphic position of OAE 1b (light gray shading) is based on biostratigraphy (Leckie, 1984; Herrle et al., 2004) combined with {delta}13 Ccarb (Herrle et al., 2004), in agreement with sections from the Vocontian Basin (Herrle et al., 2003) and ODP Site 1049 (Erbacher et al., 2001). Gray shaded interval indicates depth interval representing OAE 1B.

 

Figure 03
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  		Figure 3. TEX86–sea surface temperature (SST) (this study), selected stable oxygen and carbon isotopes of planktic foram-inifera (foram.) species Hedbergella aff. H. trocoidea (Ocean Drilling Program Site 1049, from Erbacher et al., 2001). Sea surface salinity (SSS) estimates based on selected 18O of H. aff. H. trocoidea and TEX86 using the model of Railsback et al. (1989; see text for discussion).

 
The SSS at Site 1049 was calculated following standard methods (see Bollmann and Herrle, 2007, for discussion), using a combined approach of oxygen isotopes and salinity-independent TEX86-based SST data. The SSS was calculated following Railsback et al. (1989), assuming that the {delta}18O of calcite precipitated in equilibrium with seawater is determined by a combination of seawater temperature and {delta}18O of water ({delta}w), which can be related to salinity applying a global {delta}w of –1.0{per thousand} and mean salinity of seawater of 35.0{per thousand}. To calculate SSS at Site 1049 we only used new TEX86-based SST and published {delta}18O data (planktic foraminifera Hedbergella aff. H. trocoidea; Erbacher et al., 2001) from identical or very closely spaced samples intervals.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
DISCUSSION
 CONCLUSION
 REFERENCES CITED
 
Pre-excursion bulk carbonate carbon isotope values ({delta}13 Ccarb) at Mazagan Plateau are ~2{per thousand}, rapidly decrease by ~1.5{per thousand} at the base of OAE 1b (390.7 mbsf), and remain at these relatively light values throughout most of the isotopic excursion before they reach postexcursion levels of ~1.5{per thousand} above 389.8 mbsf (Fig. 2; data from Wagner et al., 2007). Comparable {delta}13 Ccarb records were reported from the west Atlantic and Tethyan OAE 1b sites (Fig. 1B). In the lower part of the Mazagan profile the 13C record of OC ({delta}13 Corg) parallels that of {delta}13 Ccarb (Fig. 2) containing 0.5{per thousand}–1{per thousand} variations in the pre-excursion and postexcursion, a negative shift of ~1.5{per thousand} at the base of the event (390.65–390.7 mbsf). Above 390.35 mbsf, {delta}13 Corg follows a gradual return to less negative values up to –26{per thousand} in the upper part of the event (390.0 mbsf), and a general decrease toward the top of excursion.

Concentrations in total OC (TOC) are ~1.5% before OAE 1b (Fig. 2). The base of the event is marked by a 0.5% increase in TOC (at 390.56 mbsf) that proceeds in steps to almost 5% (at 389.9 mbsf) in the upper part of the isotopic excursion before it returns to the levels of the pre-excursion interval. The OC is immature (pyrolysis temperature, Tmax < 425 °C) and of type II kerogen (hydrogen indices ~300 mg HC/g TOC with values exceeding 500 mg HC/g TOC in the black shale). Isotopically heavy archaeal-derived organic matter, characteristic for nonupwelling OAE 1b sites in the western Tethys and at Blake Nose (Kuypers et al., 2001; Tsikos et al., 2004), is not present at Site 545, probably owing to overall high nutrient level of surface waters off northwest Africa at that time (Leckie, 1984). This is also supported by the abundance of sterol ethers at Site 545 that have also been identified in sediments deposited below modern upwelling regions (Schouten et al., 2005). We consider that enhanced phytoplankton production off northwest Africa masked or out-competed the invasion of archaea during the early Albian evident from less productive sites.

Carbonate carbon content varies inversely to TOC, reaching average concentrations as low as 20% in the lower part of OAE 1b before it recovers to arrive at postexcursion levels (~40%–45%) exceeding those before the excursion (~38%; Fig. 2). In contrast to TOC, the carbonate trend is hardly interrupted at the critical interval marking the onset of the event (390.6–390.7 mbsf). Strong dissolution of calcareous nannofossils was not observed across the critical transition at the base of OAE 1b (390.6–390.7 mbsf).

Averaged {delta}13C data from terrestrial plant leaf waxes (C 27, C29, C31 n-alkanes), with carbon preference indices ranging from 2.5 before and after the excursion to up to 7 within the TOC maximum, and marine algal C27-sterenes generally follow bulk {delta}13Corg (Fig. 2); i.e., they are ~–28.5{per thousand} for n-alkanes and –31{per thousand} for C27-sterenes before the OAE, then rapidly shift by 1{per thousand}–2{per thousand} to more negative values at the base of the OAE, and gradually return close to their pre-OAE values. Just below the base of the event (at 390.75 mbsf), the {delta}13C values of n-alkanes start to decline to lighter values while {delta}13C of sterenes do so ~7 cm higher in the section (at 390.68 mbsf), concomitant with the onset of OAE 1b (Fig. 2). Both molecular records reveal slightly different trends throughout the event; i.e., the {delta}13C values of the n-alkanes tend to follow {delta}13 Ccarb except for the base of the OAE, whereas those of the C27-sterenes are similar to {delta}13 Corg.

The TEX86-SST record at Site 545 (Fig. 2) reveals pre-excursion values of ~29 °C, a rapid increase by ~3.5 °C at the transition to the OAE (390.65–390 mbsf) concomitant with the negative shift in {delta}13C of steranes and persistent high SSTs between 32 and 33 °C across the event, and a variable return to ~30 °C following the isotopic excursion (from 389.9 mbsf). TEX86-SST data from OAE 1b at Site 1049 (Fig. 2) show a similar trend in SST for the lower part of the event (although the sampling resolution was lower), including an increase in SST of ~2 °C (at 143.1 mbsf) before they dropped toward the end of OAE 1b.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
CONCLUSION
 REFERENCES CITED
 
Onset of the Early Albian Carbon Reservoir Perturbation
The new Mazagan records show a negative shift for {delta}13C in various carbon reservoirs coincident with OAE 1b (Fig. 2). It has been proposed that the isotopic composition of terrestrial organic matter for the PETM is closely linked to the isotopic composition of atmospheric CO2 (Pagani et al., 2006) in the absence of major shifts in terrestrial vegetation (Schouten et al., 2007b). The sudden negative shift in 13C of n-alkanes at Site 545 is, therefore, probably best explained by a change in the 13C content of atmospheric CO2, although alternative mechanisms cannot be ruled out. The observation that the negative shift in the n-alkanes slightly precedes that of the marine records (Fig. 2) suggests that 13C-depleted carbon was abruptly released into the atmosphere and subsequently became mixed into surface waters.

The algal C27-sterene 13C record supports a sudden, though slightly delayed, response in oceanic surface waters relative to the atmosphere. Because the 13C values of n-alkanes remained at their depleted levels following the initial pulse, continuous emission of isotopically light carbon for ~25–30 k.y. is invoked to maintain this signal for the duration of OAE 1b (Wagner et al., 2007). The divergence between constant {delta}13 Ccarb and increasing {delta}13 Corg and C27-sterene 13C values probably reflects the evolution of atmospheric pCO2, consistent with modeling results (Wagner et al., 2007). Model simulations of the negative {delta}13C excursion quantified that a total of 1.3 x 1018 g methane carbon ({delta}13C of –60{per thousand}), or three times the amount of organic matter ({delta}13C =–25{per thousand}), must have been remineralized to generate the observed 13C excursion (Wagner et al., 2007). Simulation of emission as trigger for OAE volcanogenic CO2 1b did not provide realistic results consistent with the geological record and climate context; i.e., estimated volumes of greenhouse gas were unrealistically large (>300 Tmol. CO2 per yr). This emission would have led to an immediate acidification of the ocean, also leading to a positive rather than a negative isotopic excursion (K. Wallmann, 2007, personal commun.). Although the cause for the negative isotope excursion during OAE 1b remains a matter of discussion, we here focus on the impact of the global climate perturbation on SST and SSS.

Climatic Consequences of the Early Albian Emission of 13C-Depleted Carbon
Our observations at Site 545 suggest that SST responded to the injection of 13C-depleted carbon into the atmosphere with an offset represented by ~7–10 cm (390.75–390.65 mbsf; Fig. 2). Assuming linear sedimentation rates of 1.2–2.4 cm/k.y. (Wagner et al., 2007) and continuous, noninterrupted sedimentation, that offset represents ~1–3 k.y. The TEX86-SST data from Site 545 are consistent with the 32–34 °C warming at ODP Site 1049 (Fig. 2). The smaller amplitude in SST change off North America (~2 °C) in comparison to northwest Africa (~3–4 °C) may reflect prevailing upwelling of cooler waters off northwest Africa prior to the event. This mechanism probably temporarily slowed or even broke down as a consequence of OAE 1b, because upwelling processes probably did not occur off North America, explaining the generally warmer background SST. The Site 545 SST record indicates stable and extremely warm surface waters throughout most of OAE 1b, corroborating records from other OAEs that point toward long-term high SSTs (Wilson and Norris, 2001; Schouten et al., 2003), in some cases interrupted by short-term cooling events (Forster et al., 2007).

An initial increase in SST seems to be a characteristic feature not only for OAEs but also the PETM. For comparison, during the PETM, SST increased as much as 5 °C in the tropics and 8 °C in the high latitudes (Thomas et al., 2002; Zachos et al., 2006). Subtropical SST warming during the PETM was 2 °C or more higher than during OAE 1b, which is in agreement with a smaller input of 13C-depleted carbon into the atmosphere. Given the much larger global climate perturbation during the PETM, the SST increase during OAE 1b appears to be high, probably owing to strong regional amplification and positive feedback mechanisms on surface water warming (Wagner et al., 2007).

At Blake Nose, the TEX86-SST data can be compared with SST estimates derived from glassy planktic foraminiferal {delta}18O (Erbacher et al., 2001). Recalculated {delta}18O-based SST using a {delta}w value of 0.52{per thousand} (Peedee belemnite) based on corrections for latitude (Zachos et al., 1994) and temperature (Bemis et al., 1998) show as much as 4 °C warmer values compared to SST reported by Erbacher et al. (2001). These recalculated values, however, are still as much as 10 °C colder (19–24 °C) than the TEX86-SST data (32–34 °C; Fig. 3) and substantially lower than modern SST from the area (~27 °C; Levitus et al., 1998) suggesting a strong salinity effect on the {delta}18O signal. The SSS calculated from TEX86 SST and {delta}18O ranges from 41 to 43 for Blake Nose (Fig. 3), much higher than modern values of 35 (Levitus et al., 1998). A reduction in SSS from 43 to 41 at the onset of the OAE1b is observed, consistent with the proposed freshwater pulse from North America (Erbacher et al., 2001).

The TOC, SST, and SSS values dropped at the end of OAE 1b of the North Atlantic (Fig. 2), although not to pre-excursion levels. The reasons for the nonrecovery at the end of the excursion remain to be identified. As for carbon sequestration, we favor the interpretation that black shale deposition did not last long enough or was not widespread enough to fully compensate the global climate perturbation.


   CONCLUSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
REFERENCES CITED
 
The phase relationships between marine and continental OAE 1b records at Mazagan Plateau suggest that emission of 13C-depleted carbon into the atmosphere preceded the marine response by ~1–3 k.y. This lead time may have been much shorter, but based on the resolution of the data presented, it cannot be determined more accurately at present. The Mazagan and Blake Nose records provide evidence for rapid warming of surface waters and subsequently the establishment of prolonged periods (~40–45 k.y.) of high SST. Although the causal relations, response times, and timing of atmosphere-ocean interactions must still remain somewhat speculative, this study provides new detailed geochemical evidence supporting rapid, widespread, and probably almost synchronous environmental change at both sides of the low-latitude early Albian North Atlantic.


   ACKNOWLEDGMENTS
 
We thank the Integrated Ocean Drilling Program for providing the sample material and technical assistance. We also thank Klaus Wallmann and Sascha Floegel, from IFM-GEOMAR (Leibniz-Institut für Meereswissenschaften–Forschungszen-trums für marine Geowissenschaften), Kiel, for discussions and for providing unpublished simulation results, and Helga Heilmann, Brit Kockisch, and Svenja Wiegmann (Bremen), Angelika Gölden, Sonja Berg, Almuth Katzemich, Stefan Reiss (Cologne), Michiel Kienhuis, Jort Ossebaar, and Ellen Hopmans (Royal Netherlands Institute for Sea Research) for analytical assistance. This study was funded by the Deutsche Forschungsgemeinschaft (grants Wa1036/10 and Ho2188/3), the Royal Society, a Natural Sciences and Engineering Research Council Discovery grant, and the Canada Research Chairs Program (grants to Herrle). Wagner acknowledges the Royal Society-Wolfson Research Merit Award.


   FOOTNOTES
 
GSA Data Repository item 2008053, organic geochemical and isotopic procedures, is available online at www.geosociety.org/pubs/ft2008.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA. Back


   REFERENCES CITED
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSION
 REFERENCES CITED
 

Bemis, E.B., Spero, H.J., Bijma, J., and Lea, D.W., 1998, Reevaluation of the oxygen isotopic composition of planktonic foraminifera: Experimental results and revised paleo-temperature equations: Paleoceanography, v. 13 pp. 150-160 doi: 10.1029/98PA00070.[CrossRef][ISI][GeoRef]

Bollmann, J., and Herrle, J.O., 2007, Morphological variation of Emiliania huxleyi: A new tool for reconstructing sea water salinities: Earth and Planetary Science Letters, v. 255 pp. 273-288 doi: 10.1016/j.epsl.2006.12.029.[CrossRef][ISI][GeoRef]

Dickens, G.R., O'Neil, J.R., Rea, D.K., and Owen, R.M., 1995, Dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the Paleocene: Paleoceanography, v. 10 pp. 965-971 doi: 10.1029/95PA02087.[CrossRef][ISI][GeoRef]

Erbacher, J., Huber, B.T., Norris, R.D., and Markey, M., 2001, Increased thermohaline stratification as a possible cause for a Cretaceous oceanic anoxic event: Nature, v. 409 pp. 325-327 doi: 10.1038/35053041.[CrossRef][GeoRef]

Forster, A., Schouten, S., Moriya, K., Wilson, P.A., and Sinninghe Damste, J.S., 2007, Tropical warming and intermittent cooling during the Cenomanian/Turonian oceanic anoxic event 2: Sea surface temperature records from the equatorial Atlantic: Paleoceanography, v. 22p. PA1219 doi: 10.1029/2006PA001349.[CrossRef]

Herrle, J.O., Pross, J., Friedrich, O., Kößler, P., and Hemleben, C., 2003, Forcing mechanisms for mid-Cretaceous black shale formation: Evidence from the Upper Aptian and Lower Albian of the Vocontian Basin (SE France): Palaeogeography, Palaeoclimatology, Palaeoecology, v. 190 pp. 399-426 doi: 10.1016/S0031–0182(02)00616–8.[CrossRef][GeoRef]

Herrle, J.O., Kößler, P., Friedrich, O., Erlenkeuser, H., and Hemleben, C., 2004, High-resolution carbon isotope records of the Aptian to Lower Albian from SE France and the Mazagan Plateau (DSDP Site 545): A stratigraphic tool for paleoceanographic and paleobiologic reconstruction: Earth and Planetary Science Letters, v. 218 pp. 149-161 doi: 10.1016/S0012–821X(03)00646–0.[CrossRef][ISI][GeoRef]

Jenkyns, H.C., 2003, Evidence for rapid climate change in the Mesozoic–Palaeogene greenhouse world: Royal Society of London Philosophical Transactions, ser. A, v. 361 pp. 1885-1916 doi: 10.1098/rsta.2003.1240.[CrossRef]

Kuypers, M.M.M., Blokker, P., Erbacher, J., Kinkel, H., Pancost, R.D., Schouten, S., and Damsté, J.S.S., 2001, Massive expansion of marine Archaea during a mid-Cretaceous oceanic anoxic event: Science, v. 293 pp. 92-94 doi: 10.1126/science.1058424.[Abstract/Free Full Text][CrossRef][ISI][Medline][GeoRef]

Leckie, R.M., 1984, Mid-Cretaceous planktonic foraminiferal biostratigraphy off central Morocco, Deep Sea Drilling Project 79, Sites 545 and 547: in Hinz, K., and Winterer, E.L., Initial reports of the Deep Sea Drilling Project, Volume 79: Washington, D.C., U.S. Government Printing Office, pp. 579-620.

Leckie, R.M., Bralower, T.J., and Cashman, R., 2002, Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous: Paleoceanography, v. 17, no. 3p. 1041 doi:10.1029/2001PA000623.[CrossRef]

Levitus, S., Boyer, T., Burgett, R., and Conkright, M., 1998, World ocean atlas 1998 (WOA98): Ocean Climate Laboratory, National Oceanographic Data Center (data accessible at http://ferret.wrc.noaa.gov/las/main.html).

Pagani, M., Pedentchouk, N., Huber, M., Sluijs, A., Schouten, S., Brinkhuis, H., Sinninghe Damsté, J.S., and Dickens, G.R., and IODP Expedition 3022006, Arctic's hydrology during global warming at the Palaeocene–Eocene thermal maximum: Nature, v. 442 pp. 671-675 doi: 10.1038/nature05043.[CrossRef][Medline]

Railsback, L.B., Anderson, T.F., Ackerly, S.C., and Cisne, J.L., 1989, Paleoceanographic modeling of temperature-salinity profiles from stable isotope data: Paleoceanography, v. 4 pp. 585-591.[GeoRef]

Schouten, S., Hopmans, E.C., Forster, A., van Breugel, Y., Kuypers, M.M.M., and Sinninghe Damsté, J.S., 2003, Extremely high sea-surface temperatures at low latitudes during the middle Cretaceous as revealed by archaeal membrane lipids: Geology, v. 31 pp. 1069-1072 doi: 10.1130/G19876.1.[Abstract/Free Full Text][CrossRef][ISI][GeoRef]

Schouten, S., Rampen, S.W., Geenevasen, J.A.J., and Sinninghe Damste, J.S., 2005, Structural identification of steryl alkyl ethers in marine sediments: Organic Geochemistry, v. 36 pp. 1323-1333 doi: 10.1016/j.orggeochem.2005.04.002.[CrossRef][ISI]

Schouten, S., Huguet, C., Hopmans, E.C., and Sinninghe Damsté, J.S., 2007a, Improved analytical methodology of the TEX86 paleothermometry by high performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry: Analytical Chemistry, v. 79 pp. 2940-2944 doi: 10.1021/ac062339v.[Medline]

Schouten, S., Woltering, M., Rijpstra, W.I.C., Sluijs, A., Brinkhuis, H., and Sinninghe Damsté, J.S., 2007b, The Paleocene–Eocene carbon isotope excursion in higher plant organic matter: Differential fractionation of angiosperms and conifers in the Arctic: Earth and Planetary Science Letters, v. 258 pp. 581-592 doi: 10.1016/j.epsl.2007.04.024.[CrossRef][ISI][GeoRef]

Shipboard Scientific Party, 1984, Site 545: in Hinz, K., and Winterer, E.L., Initial reports of the Deep Sea Drilling Project, Volume 79: Washington, D.C., U.S. Government Printing Office pp. 81-177.

Thomas, D.J., Zachos, J.C., Bralower, T.J., Thomas, E., and Bohaty, S., 2002, Warming the fuel for the fire: Evidence for the thermal dissociation of methane hydrate during the Paleocene-Eocene thermal maximum: Geology, v. 30 pp. 1067-1070.[Abstract/Free Full Text][CrossRef][ISI][GeoRef]

Tsikos, H., Karakitsios, V., van Breugel, Y., Walsworth-Bell, B., Bombardiere, L., Petrizzo, M.R., Damste, J.S.S., Schouten, S., Erba, E., Silva, I.P., Farrimond, P., Tyson, R.V., and Jenkyns, H.C., 2004, Organic carbon deposition in the Cretaceous of the Ionian Basin, NW Greece: The Paquier Event (OAE 1b) revisited: Geological Magazine, v. 141 pp. 401-416 doi: 10.1017/S0016756804009409.[Abstract/Free Full Text][CrossRef][ISI][GeoRef]

Wagner, T., Wallmann, K., Stüsser, I., Herrle, J.O., and Hofmann, P., 2007, Consequences of moderate 25,000 yr lasting emission of light CO2 into the mid-Cretaceous ocean: Earth and Planetary Science Letters, v. 259 pp. 200-211 doi: 10.1016/j.epsl.2007.04.045.[CrossRef][ISI][GeoRef]

Wilson, P.A., and Norris, R.D., 2001, Warm tropical ocean surface and global anoxia during the mid-Cretaceous period: Nature, v. 412 pp. 425-428 doi: 10.1038/35086553.[CrossRef][GeoRef]

Zachos, J.C., Stott, L.D., and Lohmann, K.C, 1994, Evolution of early Cenozoic marine temperatures: Paleoceanography, v. 9 pp. 353-387 doi: 10.1029/93PA03266.[CrossRef][ISI][GeoRef]

Zachos, J.C., Schouten, S., Bohaty, S., Quattlebaum, T., Sluijs, A., Brinkhuis, H., Gibbs, S.J., and Bralower, T.J., 2006, Extreme warming of mid-latitude coastal ocean during the Paleocene-Eocene Thermal Maximum: Inferences from TEX86 and isotope data: Geology, v. 34 pp. 737-740 doi: 10.1130/G22522.1.[Abstract/Free Full Text][CrossRef][ISI][GeoRef]

Received for publication 19 February 2007

Revised manuscript received 30 October 2007

Manuscript accepted 30 October 2007





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