Th or collective redistirbution or collective of this by of any article portion SPECIAL ISSUE FEATURE in published been has is article , Volume 4, a quarterly journal of Th 19, Number

Greenhouse or other means reposting, is only photocopy machine, permitted AND THE World e Oceanography Society. Copyright 2006 by Th Society. e Oceanography


Earth’s has alternated between hurricanes, and enhanced amounts of icant achievements of DSDP and ODP Th of approval the with greenhouse (warm) and icehouse (cool) . Understanding the ocean- research and discusses future prospects modes throughout the (Fig- climate during greenhouse for Integrated Ocean Drilling Program ure 1A). At present, Earth is in the midst climate modes is essential for more accu- (IODP) investigations in the fi eld of Me- Permission reserved. Society. All rights e Oceanography is gran of an icehouse climate. Nevertheless, the rately predicting future climate and envi- sozoic . all correspondence to: Society. Send [email protected] e Oceanography or Th rise of industrialization in the last two ronmental changes in a warming Earth. centuries has led to a dramatic increase The Mesozoic-early is NEW INSIGHTS in atmospheric CO2 from the burning known as a typical greenhouse pe- Determination of Mesozoic Ocean of fuels, which, in turn, has led to riod caused largely by increased CO2 History signifi cant global warming (e.g., Rud- from elevated global igneous activity An important DSDP and ODP achieve- diman, 2000). Global warming could (Figure 1A–C). The mid- is ment was the reconstruction of the his- profoundly impact as a result marked by a major warming peak (Fig- tory of Mesozoic ocean temperature of consequent global -level rise, more ure 1D); it is characterized by globally changes based on geochemical methods numerous and increasingly powerful averaged surface more such as , TEX86, and al- ted in teaching to and research. copy this for use Repu article than 14°C higher than those of today kenone analyses. Oxygen- data Reishi Takashima (rtaka@.sci. (Tarduno et al., 1998), a lack of perma- have provided the greatest source of hokudai.ac.jp) is Research Fellow, Depart- nent sheets (Frakes et al., 1992), and paleotemperature reconstructions from MD 20849-1931, USA. 1931, Rockville, Box PO Society, e Oceanography ment of Earth and Planetary Sciences, Hok- ~ 100–200-m-higher than that ancient . However, the increasing kaido University, Sapporo, Japan. Hiroshi of today (Haq et al., 1987; Miller et al., prevalence of diagenetic alteration in Nishi is Associate Professor, Department 2005a) (Figure 1E). Studies using Deep older or more deeply buried rocks limits of Earth and Planetary Sciences, Hokkaido Sea Drilling Project (DSDP) and Ocean or prevents reliable isotopic data from University, Sapporo, Japan. Brian T. Huber Drilling Program (ODP) cores have being gleaned from biogenic pre- is Curator, Smithsonian Institution, National advanced understanding of Mesozoic served in terrestrial outcrops. Compared Museum of Natural History, Washington, oceanography and climate, demonstrat- to many land-based sections, blication, systemmatic reproduction, D.C., USA. R. Mark Leckie is Professor, ing that Mesozoic ocean circulation and of Cretaceous age recovered Department of Geosciences, University of marine ecosystems differed greatly from from samples drilled at DSDP and ODP Massachusetts, Amherst, MA, USA. those of today. This paper reviews signif- sites are often better preserved, and usu-

82 Oceanography Vol. 19, No. 4, Dec. 2006 30 Figure 1. Compilation G Percent of world’s (%) ( ) showing the changes original 20 in climate, and geologi- reserves generated by cal and paleontologi- source rocks (Klemme cal events through the and Ulminshek,1991) 10 Gas Phanerozoic. Oil


60 P/T F Percentage (%) ( ) K/P T/J Late of marine genera (Raup Hot and Sepkoski, 1986) and 40 major Oceanic Anoxic OAE2 Events 20 OAE1a–1d Weissert

0 30˚ 200 Glaciation (m) Sea Level 40 (E) Sea level changes 50 and continental 100 glaciation (Ridgwell, 60 Sea Level 2005) 70

0 (°paleolatitude)

80 Glaciation Continental -100 90

(D) Temperature (Frakes et al., 1992) Warm Cold

20 6000 (C) 2 CO2

Ratio of the mass ) 2 of atmospheric CO 4000 2 10

at a past time to (RCO

that at present RCO2 Smoothed CO 2000 representation (Royer, in press) (Royer,

(Berner, in press) record of the

0 0 (ppm) 5

(B) Production rate of

/) 4 (Stanley, 1999) 3 (km

3 (A) Climate mode I GreenhouseIcehouse GreenhouseI Greenhouse Ice. (Frakes et al., 1992) Paleog Creta Jur Carboni- Cambria Devonian ass ferous c eou ene ic s n

Cenozoic Mesozoic

0 (Ma)100 200 300 400 500 600

Oceanography Vol. 19, No. 4, Dec. 2006 83 ally have not been as seriously affected 2003; Jenkyns et al., 2004). where the difference of temperature be- by complex tectonic and/or weather- According to isotopic records of sur- tween the mid-Cretaceous and the pres- ing processes. Exquisitely preserved face-dwelling planktic , sea ent oceans is nearly 30°C (Figure 2). Bice foraminifera from the low- surface temperatures reached a maxi- and Norris (2002) estimate that at least

Demerara Rise (ODP Sites 1258–1261; mum of 42°C at the Demerara Rise (Bice 4500 ppm CO2 would be required to 4–15°N), mid-latitude Blake Nose (ODP et al., 2006), 33°C at the Blake Nose (Hu- match the above-mentioned maximum Sites 1049, 1050, 1052; 30°N), and ber et al., 2002), and 31°C at the Falkland temperatures, which is 11 times greater high-latitude Falkland Plateau (DSDP Plateau (Huber et al., 2002; Bice et al., than the modern atmospheric concen- Site 511; 60°S) in the 2003) during the (~ 93–89 Ma tration. Using a more recent climate have been especially useful for recon- [million ago]) (Figures 2 and 3). model, Bice et al. (2006) conclude that structing vertical and latitudinal tem- At comparable in the modern 3500 ppm or greater atmospheric CO2 perature gradients of the mid- through ocean, August surface tempera- concentration is required to reproduce ocean (Figures 2 and 3). tures are 25–28°C at 0–20°N, 20–28°C at the estimated maximum sea surface tem-

The TEX86 method is especially useful 20–40°N, and 0–5°C at 60°S (Thurman peratures of the Mesozoic tropical ocean. for organic carbon-rich and and Trujillo, 1999). Consequently, these Because the Mesozoic paleo-tem- has provided excellent paleo-tempera- data suggest that Cretaceous warming perature estimates based on geochemical ture determinations (e.g., Schouten et al., was most prominent at high latitudes proxies are still insuffi cient in sediments older than (> 112 Ma) and in ar- eas outside of the Atlantic Ocean, further investigations are needed to reconstruct a reliable spatial and temporal tempera- Mid-Cretaceous ture history during the greenhouse cli- 35 sea-suface mate of the Mesozoic. temperature ? gradient 30 Oceanic Anoxic Events Defi ning the concept of Oceanic Anoxic 25 Events (OAEs) was one of the most im- portant achievements of the early DSDP. 20 Cretaceous marine sediments in

Temperature (˚C) Temperature are mainly comprised of white lime- 15 Present stone and ; however, distinct black, sea-surface temperature laminated organic-rich layers, termed 10 gradient 1260 390/1049 1257 392 “black ,” are occasionally interca- 144 1050 690 Fl-533 689258 511 528 356 463 17 1258 627 1052 lated within these sequences (Figure 4). 5 Because organic carbon is preferentially 80˚S 60˚S 40˚S 20˚S 020˚N 40˚N 60˚N 80˚N preserved under anoxic conditions, ear- Latitude lier workers suggested that these black ODP/DSDP sites other core sites shales had accumulated locally in a

Paleo sea-surface temperature weakly ventilated, restricted basin under Turonian late Albian regional anoxic conditions. In the mid- 1970s, however, the discovery of black Figure 2. Latitudinal variations of surface ocean paleotemperature derived from oxy- shales at many DSDP drill sites from gen isotopes of planktonic foraminifera and TEX86. Modifi ed from Huber et al. (2002), Bice et al. (2003), and Jenkyns et al. (2004). the Atlantic, Indian, and Pacifi c Oceans

84 Oceanography Vol. 19, No. 4, Dec. 2006 led to recognition of widespread anoxic Burial of organic carbon, which pref- trial rocks such as dark gray- to black- conditions in the global ocean spanning erentially sequesters isotopically light colored mudstones, carbon isotope limited stratigraphic horizons (Figure 5). carbon during OAEs, resulted in a posi- excursions are a useful marker for rec- Schlanger and Jenkyns (1976) termed tive δ13C (13C/12C) excursion of 2–3‰ ognizing OAEs (e.g., Gröke et al., 1999; these widespread depositional black in the (Figure 3). Even Takashima et al., 2004). Recent advances shale intervals “Oceanic Anoxic Events.” if black shales are not visible in terres- in and correlation us-

Bulk Carbon Isotope Ocean Crust Production Paleo-temperature (Huber et al., 2002) (green line) Sea Level (Stanley and Hardie 1998) and Platform Oceanic Anoxic Age (m) Blake Plateau S. high latitude (km2/year) Drowning (red arrow) Events (Site 1049) (Site 511 and 690) 13 D Ccarbonate -100 0m 100 200 3.5 4 4.5 1014 18 22 26 30 (˚C) 618222610 14 (˚C) 0 1 2 3 4(‰) North 60 Atlantic Regio- Global gene nal 9 Maastrichitian Deccan Trap 70

Campanian 8 80 Upper OAE3 90 7 Turonian Caribbean Plateau OAE2 Cenomanian MCE 100 OAE1d Albian Miller et al. OAE1c (2005) 110 6

Cretaceous Paleo- OAE1b Rajmahal Trap Ontong 120 Benthic foraminifera Fallot Java OAE1a Lower Planktic foraminifera Plateau 130 Faraoni Paraná Flood Weissert 140 Basalt 5

Tithonian 150 second order

Upper Hardenbol Oxfordian 4 160 et al. (1998) ? third order 170 Middle 3

180 Toarcian Toarcian OAE 2 ? 190 Circum

Lower ? Hattanngian Atlantic 1 200 Magmatic Triassic Province

0 246(x106km2) Large Igneous Provinces (Jones and Jenkyns, 2001) Figure 3. Compilation showing Jurassic–Cretaceous changes in sea level, oceanic-crust production, paleo-temperature, bulk carbon isotopes, carbonate- platform drowning events and OAEs. data are from Jones and Jenkyns (2001). Bulk carbon isotopes are from (1) Van de Schoot- brugge et al. (2005); (2) Hesselbo et al. (2000); (3) Morettini et al. (2002); (4) Dromart et al. (2003); (5) Weissert et al. (1998); (6) Erbacher et al. (1996); (7) Jenkyns et al. (1994); (8) Jarvis et al. (2002); and (9) Abramovich et al. (2003). Carbonate-platform drowning data are from Simó et al. (1993) and Weis- sert and Mohr (1996).

Oceanography Vol. 19, No. 4, Dec. 2006 85 Figure 4. Cretaceous black shales intercalated in pelagic sequence, central Italy. Figure courtesy of R. Coccioni.

2 1a–1d OAE OAE

ing carbon isotopes have revealed that modern examples for this model. have further consumed dissolved oxygen OAEs occurred at least eight times in the These two models predict differ- in the water column, while simultane-

Cretaceous and at least one to four times ent vertical thermal gradient profi les of ously releasing CO2 to the in the Jurassic (Figure 3). The Toarcian the water column that can be inferred (Gale, 2000; Jahren, 2002). However, be- OAE, Weissert OAE, OAE 1a, and OAE 2 from the oxygen isotopes of planktic cause there really is no modern analog are global-scale anoxic events associated and benthic foraminifera. For example, for global ocean anoxia, these models with prominent positive excursions of the OAE 1b in the earliest Albian (about suffer accordingly. δ13C and worldwide distribution of black 112 Ma) is characterized by a sudden OAEs have had a signifi cant infl u- shales (Figure 3). increase in surface water temperatures ence on the and diversity of Two models, that of a stagnant ocean and strengthening of the vertical strati- ancient marine communities through and expansion of the oxygen-minimum fi cation of the water column (Erbacher the Phanerozoic. Numerous records layer, have been proposed to explain et al., 2001), suggesting similarity to the demonstrate a high turnover rate of mi- black shale in the OAEs (e.g., Pedersen STO model (Figure 7A). On the other crofossils at or near OAE intervals (Jarvis and Calvert, 1990). The stagnant ocean hand, the OAE 2 (about 93.5 Ma) shows et al., 1988; Erbacher et al., 1996; Pre- model (STO model) attributes OAEs to sudden warming of deep water and col- moli Silva and Sliter, 1999; Leckie et al., depletion of bottom water oxygen as a lapse of vertical stratifi cation (Huber 2002; Erba, 2004). During the Cenoma- result of dense vertical ocean stratifi ca- et al., 1999), which probably induced nian-Turonian (C/T) boundary OAE 2, tion (Figure 6A). A modern analog is enhanced and productivity for example, anoxic environments ex- seen in stratifi ed silled basins such as the similar to the expanded OMZ model panded from the photic zone (Damsté . The expanded oxygen-mini- (Figure 7B). Deep-water warming may and Köster, 1998; Pancost et al., 2004) to mum layer model (OMZ model) pro- have contributed to a decrease in oxygen greater than 3500-m depth in the Atlan- poses that increased surface ocean pro- solubility in the deep ocean and may tic Ocean (Thurow et al., 1992), resulting ductivity caused expansion of the oxy- have triggered the disassociation of large in about 20 percent of marine organisms gen-minimum layer in the water column volumes of hydrate buried in becoming extinct in various habitats (Figure 6B). Upwelling sites such as the sediments of the continental margins. within an interval of less than one mil- Moroccan and Peruvian margins provide Oxidation of the released methane could years (Figure 1F). Black shales in the

86 Oceanography Vol. 19, No. 4, Dec. 2006 N. America

Blake Nose

Pacific Ocean Te thy Atlantic Ocean s S ea Demerara Rise

Caribbean Pacific Ocean Plateau S. America Manikihi Paraná flood Plateau basalt


Kerguelen Falkland Plateau Plateau

TOC Increase in Ranges Shallow Ocean Black Shale and/or Organic Rich Sediment LIPs (Pre-Cenomanian) Epi-Continental Sea Mid-Ocean Ridges LIPs (Cenomanian–Turonian) Land Zones Deep Ocean

Figure 5. Distribution of black shales and/or increased organic carbon sediments at OAE 2. Data are from Schlanger et al. (1987); Arthur et al. (1987, 1988); Jenkyns, (1991); Th urow et al. (1992); Kassab and Obaidalla (2001); Wang et al. (2001); Lebedeva and Zverev (2003); Yurtsever et al. (2003); Coccioni and Luciani (2005); Fisher et al. (2005); and Takashima and Nishi (unpublished data).

(A) Stagnant ocean model (B) Expanded oxygen minimum layer model

high productivity


oxic anoxic Strengthened thermocline Weakened thermocline nutrient anoxic Black Shales oxic Black Shales

Figure 6. Representative models for black shale deposition: (A) the stagnant ocean model, and (B) the oxygen-minimum-layer model.

Oceanography Vol. 19, No. 4, Dec. 2006 87 (A) OAE 1b (Strengthened water column stratification) (B) OAE 2 (Collapse of water column stratification) Oxygen Isotope Oxygen Isotope Planktonic Records Planktonic Records Lithology Foraminifera D18Oforaminifera (‰) Lithology Foraminifera D18Oforaminifera (‰)

Stages -0.8-1.2 -1.6 -2.0 -2.4

0.0 -0.8 -1.6 Depth (mbsf) Depth (mbsf)


500.4 Helveto- globotruncana 500.6 helvetica Turonian Stages strengthened r Lower Albian vertical stratification ve 500.8 143 W. archaeocretacea collapse of collapse 501.0 planispira vertical stratification surface water warming 501.2 Rotalipora cushmani 144 501.4

Upper deep water Cenomanian Aptian warming 501.6

10 14 18 22 16 18 20 22 T (°C) T (°C) shallower habitant Figure 7. Vertical ocean temperature structure, reconstructed deeper from oxygen isotopes, during (A) OAE 1b (Erbacher et al., 2001) planktic

habitant foraminifera and (B) OAE 2 (Huber et al., 1999) intervals at the Blake Nose, western North Atlantic. benthic foraminifera

Black shale


Limestone Slump

OAEs, especially OAE 1a and OAE 2, fre- the black shales provides strong support ing OAEs may have drawn down CO2 quently yield no calcareous nannofossils, for this hypothesis. These proxies further from the ocean–atmosphere by burying planktic foraminifera, or radiolarians, indicate that anoxic conditions occa- organic carbon in black shales, thereby suggesting that anoxic conditions had sionally occurred at very shallow water punctuating long-term global warmth expanded to within the euphotic zone of depths during the C/T OAE. (e.g., Arthur et al., 1988; McElwain et al., the surface water column (e.g., Hart and OAEs also served as an effective ther- 2005). The Late Devonian Leary, 1991; Coccioni and Luciani, 2005). mostat for the greenhouse Earth. Be- could be an extreme example where Discovery of abundant cause the change in organic burial in the widespread anoxia caused not only sig- biomarkers (e.g., Kuypers et al., 2004), OAE pelagic sections was two to three nifi cant biotic extinction (about 40 per- nonthermophilic archaea (e.g., Kuypers orders of magnitude greater than the cent), but also induced glaciation after et al., 2001), and green bacteria mean conditions at other time intervals, deposition of black shales (Caplan and (e.g., Damesté and Köster, 1998) within burial of massive organic carbon dur- Bustin, 2001).

88 Oceanography Vol. 19, No. 4, Dec. 2006 OAEs have benefi ted human life be- and intra-continental seaways (e.g., Hays an ice-free interval, the mechanisms for cause they are a major cause of the large and Pitmann III, 1973) (Figure 5). the large and rapid observed sea-level volumes of oil and gas that we consume The most widely cited reconstructions changes during the Cretaceous have long today. These hydrocarbons were derived of past sea-level changes were established been debated (e.g., Skelton et al., 2003). from organic-rich sediments that formed by Exxon Production Research Company Miller and his colleagues demonstrated under anoxic conditions. Indeed, many (EPR) (Haq et al., 1987), which have that several rapid sea-level falls recorded petroleum source rocks were formed since been refi ned (e.g., Hardenbol et on the New Jersey margin could be ex- during greenhouse warming peaks be- al., 1998). These sea-level plots consist plained only by glacio-eustacy (Miller tween the and mid-Cre- of short- (105–106 year) and long-term et al., 1999; 2005a). Through integra- taceous (Figure 1G). (107–108 year) curves that are correlated tion of data on occurrences of ice-rafted with detailed chrono-, bio-, and magne- and/or glacial deposits around polar re- Mesozoic Sea-Level Changes and tostratigraphies for last 250 million years gions, positive oxygen isotope values of the Existence of Ice Sheets (Figure 3). According to the EPR curves, foraminifera, and intervals of rapid sea- Rising sea level attributed to global Late Cretaceous sea level rose as much as level fall, it is quite possible that warming is one of the most serious 260 m above the present level. The EPR waxed and waned during the greenhouse and imminent problems for mankind curves, however, have been criticized climate of the Mesozoic. Although un- because of the concentration of hu- because: (1) the supporting data are certainty remains in age and ice volume, man populations in coastal areas. Fluc- proprietary, (2) the sequence boundar- several geologically short-term glacial tuations in global sea level result from ies do not translate into eustatic (glob- events during the Cretaceous have been changes in the volume of the ocean or al) sea-level changes, and (3) inferred proposed (e.g., middle Cenomanian the volume of ocean basins. The former amplitudes of sea-level fl uctuations [96 Ma], middle Turonian [91–90 Ma], depends mainly on the growth and de- appear to be conjecture (e.g., Christie- middle [the Campanian is cay of continental ice sheets over short Blick et al., 1990). ODP drilling on the from 83.5–70.8 Ma], and earliest and (104–105 year) timescales, while the lat- New Jersey passive continental margin late Maastrichtian [70.6 and 66.1 Ma]). ter fl uctuates on longer (106–107 year) (ODP 174AX) provided new insights These results imply that greenhouse pe- timescales resulting from tectonic effects into the amplitudes of, and mechanisms riods can exhibit signifi cant short-term such as variations in seafl oor-spreading for, sea-level changes for last 100 million climatic variability, in contrast to previ- rates, ocean-ridge lengths, and collision/ years. The area around the drilling sites ously proposed models suggesting long- break-up of (e.g., Ruddiman, is an excellent location for sea-level stud- term stable and equable . 2000; Miller et al., 2005a, b). Because ies because of quiescent and the Mesozoic exhibited the break-up well-constructed biostratigraphic and Biocalcification Crises During the of , predominantly ice-free Sr isotopic age control (Sugarman et al., Mesozoic Ocean climates, high rates of seafl oor spread- 1995). The proposed sea-level curve de- The Mesozoic is marked by the poleward ing, as well as the emplacement of large veloped using data collected during New expansion of shallow-water carbonate igneous plateaus on the ocean fl oor Jersey drilling is well correlated with platforms as well as several occurrences (see Coffi n et al., this issue), the Meso- those of Russian and EPR curves, but of their global “drowning” or “collapse” zoic ocean was characterized by much the estimated maximum global sea-level events (e.g., Johnson et al., 1996; Simo et higher sea level than at present. Sea amplitude is ~ 100 m during Late Cre- al., 1993). These drowning events were level peaked in mid- to Late Cretaceous taceous (Miller et al., 2005a) (Figure 3), not due to sea-level rise because shal- (~ 100–75 Ma) when the total land area in contrast to the much greater sea-level low-water carbonate platforms usually fl ooded was more than 40 percent great- amplitude estimated by EPR. grow upwards much faster than sea level er than at present, resulting in the expan- Because the Mesozoic greenhouse pe- rises. Although of surface sion of environments riod is generally assumed to have been oceans associated OAEs were considered

Oceanography Vol. 19, No. 4, Dec. 2006 89 to be the cause of these drowning events, al. (2006) estimated that Cretaceous CO2 drilling targets. Submerged continental ODP Legs 143 and 144 revealed that atmospheric concentration ranged be- sites such as the Somali Basin should some shallow-water carbonate platforms tween 600 and 2400 ppm, 1.5 to 6 times also be targeted as they record a continu- survived during OAE 1a in the central the present concentration. If the current ous paleoceanographic history from the

Pacifi c (Wilson et al., 1998). Weissert rate of CO2 increase continues, Creta- or older. We expect that and Erba (2004) pointed out that the ceous values may be attained within new IODP research from these Creta- coincidence between drowning events 1500–6000 years, but current trends are ceous sites could provide new insights of shallow-water carbonate platforms already having clear affects on both the to the process of abrupt global warming and the crisis of heavily calcifi ed plank- ocean- and the . and its impact on Earth’s biosphere. ton groups, and termed these events In fact, a recent ocean- “biocalcifi cation crises.” Although the predicts that rapid atmospheric release ACKNOWLEDGEMENTS mechanism responsible for biocalcifi ca- of CO2 will produce changes in ocean We express sincere gratitude to Dr. R. tion crises remains poorly constrained, chemistry that could affect marine eco- Coccioni for providing photographs of recent hypotheses point to elevated systems signifi cantly, even under future black shales in Italy. Extremely helpful pCO2-induced lowered surface ocean pathways in which most of the remain- reviews by two anonymous reviewers pH, which affected carbonate-secreting ing CO2 is never released (Cal- and the editorial assistance of Drs. R. organisms (e.g., Leckie et al., 2002; Weis- deira and Wickett, 2005). Burger and K. Fujioka helped to improve sert and Erba, 2004). Improved understanding of the Me- the quality of the manuscript. sozoic ocean-climate system and forma- FUTURE PROSPECTS OF tion of OAEs is important to better pre- REFERENCES THE IODP FOR MESOZOIC dict environmental and biotic changes Abramovich, S., G. Keller, D. Stüben and Z. Berner. 2003. Characterization of late Campanian and OCEANOGRAPHY in a future greenhouse world. However, Maastrichtian planktonic foraminiferal depth The greenhouse climate of the mid-Cre- Cretaceous DSDP and ODP cores with habitats and vital activities based on stable iso- taceous was likely related to major global continuous recovery and abundant well- topes. , Palaeoclimatology, Pal- aeoecology 202:1–29. and associated outgassing preserved suitable for isotopic Arthur, M.A., S.O. Schlanger, and H.C. Jenkyns. 1987. The Cenomanian–Turonian oceanic an- of CO2. OAEs may be recognized as a study are very limited. To better under- negative feedback in response to sudden stand the ocean-climate dynamics of the oxic event, II. Palaeoceanographic controls on organic-matter production and preservation. warming episodes by preventing further Mesozoic greenhouse Earth, a denser Pp. 401–422 in Marine Petroleum Source Rocks, acceleration of warming through remov- global array of deep-sea cores is needed J. Brooks and A. J. Fleet, eds. Geological Soci- ety Special Publication 26. Blackwell, Oxford, al of organic carbon from the ocean-at- to provide more detailed reconstructions United Kingdom. mosphere (CO2) reservoir to sediment of global climate changes and oceano- Arthur, M.A., W.E. Dean, and L.M. Pratt. 1988. reservoirs. This process resulted in the graphic conditions. Though far from Geochemical and climatic effects of increased marine organic carbon burial at the Cenoma- emplacement of a large volume of or- complete, the Mesozoic paleoceano- nian/Turonian boundary. Nature 335:714–717. ganic matter during the mid-Cretaceous, graphic record is much better studied in Berner, R.A. In press. GEOCARBSULF: A com- bined model for Phanerozoic atmospheric O which now serves as a major source of areas of the Atlantic Ocean and Tethys 2 and CO2. Geochimica et Cosmochimica Acta. fossil fuels (Larson, 1991). However, Sea than in the Indo–Pacifi c Oceans be- Bice, K.L., and R.D. Norris. 2002. Possible atmo- present human activities are rapidly con- cause most seafl oor formed there in the spheric CO2 extremes of the middle Cretaceous suming these fuels, returning the carbon Mesozoic has already been subducted (late Albian-Turonian). Paleoceanography 17:1029/2002PA000778. to the ocean-climate system. Pre-indus- (Bralower et al., 1993). Mesozoic marine Bice, K.L., B.T. Huber, and R.D. Norris. 2003. Ex- treme polar warmth during the Cretaceous trial CO2 levels of about 280 ppm have sequences deposited at middle to high increased over the past 200 years to the latitudes of the Pacifi c Ocean, such as the greenhouse?: Paradox of the Late Turonian δ18O record at DSDP Site 511. Paleoceanography current levels exceeding 380 ppm, main- continental margin of eastern Asia and 18:1029/2002PA000848. ly as a result of human activities. Bice et the Bering Sea, are appropriate future Bice, K.L., D. Birgel, P.A. Meyers, K.A. Dahl,

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