Coastal upwelling and atmospheric CO2 changes over the last 400,000 years: Peru

Marine Geology, 107 (1992) 239-248

239

Elsevier Science Publishers B.V., Amsterdam

Coastal upwelling and atmospheric CO 2 changes over the last 400,000 years: Peru Hans Schrader Department of Geology, University of Bergen, All~gaten 41, N-5007 Bergen, Norway (Received January 21, 1992; revision accepted April 27, 1992)

ABSTRACT Schrader, H., 1992. Coastal upwelling and atmospheric CO2 changes over the last 400,000 years: Peru. Mar. Geol., 107: 239-248. A transfer function relating diatom assemblages in surface sediments and primary production in the photic zone was used to calculate variations in primary production in hole ODP Leg 112, Site 681A over the last 400 kyr. Primary production off central Peru was enhanced during peak glaciations and it decreased during peak interglaciais, but low and high production periods also occurred in both glacials and interglacials. The close resemblance of the primary production curve off Peru to the atmospheric CO2 Vostok record suggests a relationship between the Peruvian neritic biological pump and atmospheric pCO2.

Introduction

Changes in the level of biological activity in coastal upwelling areas of the eastern boundary current systems (the Californian, Peruvian, Namibian and northwest African coastal areas) influence the transfer of atmospheric carbon via biological fixation and storage into organic carbon rich sediments (Sarnthein et al., 1988). The upwelling in the Peruvian system is one of the strongest in the world (Barber and Smith, 1981) and has been effective since the middle Miocene (Suess et al., 1988) or perhaps even since the late Eocene (Dunbar et al., 1990). Hemipelagic sediments rich in organic carbon were deposited on the shelves and upper slopes with high accumulation rates that contain a well preserved marine planktonic diatom flora. The relationship between temporal changes in oceanic biological activity in the photic zone and atmospheric pC02 content has been documented for the eastern Equatorial Pacific (Shackleton and Pisias, 1985), the low latitude Atlantic (Mix, 1989) Correspondence to: H. Schrader, Department of Geology, University of Bergen, All6gt. 41, N-5007 Bergen, Norway. 0025-3227/92/$05.00

and the area off northwest Africa (Sarnthein et al., 1987) by analyzing the variation of organic carbon accumulations, the transfer function of planktonic foraminifera and export production and the difference of 6 Iac between planktonic and benthic foraminifera from carbonate- rich deep-sea cores. Changes in the magnitude of the coastal biological pump (Berger and Vincent, 1986) should be greatest in geological records directly underlying coastal upwelling areas. Material and results

During ODP Leg 112 three sites were cored within the upper slope mud lenses where hemipelagic sediments have accumulated over the last > 1 million years (Fig. 1; Suess et al., 1988) and where one of the strongest modern coastal upwelling prevails (Suess et al., 1990). These sites include Site 681 from 150.5 m, Site 680 from 252.5 m and Site 686 from 446.8 m water depth. This undisturbed Peruvian geological record is characterized by high sedimentation rates (70-50 ram/10 a yr over the upper 27 m), high organic carbon content (average over last 400 kyr at Site 680:4.8 and Site

© 1992 - - Elsevier Science Publishers B.V. All rights reserved.

H. SCHRADER

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Fig. I. Location of the hydraulic piston core sites (680A, 681A and 686A) of O D P Leg 112 off the central Peruvian coast. Bathymetry in meters.

681:3.4 wt%, respectively: Heinze, 1990; Wefer et al., 1990) and an abundant, well preserved marine planktonic diatom flora. The Peruvian coastal upwelling area has an annual primary production exceeding 300 gC/m2/ yr (Zuta and Guill6n, 1970) in well-defined coastal lobes at 9 °, l i° and 16°S. It has been the subject of much oceanographic and biologic monitoring (Blasco, 1971; Barber and Smith, 1981). Two drill holes (681A and 686A) were continuously sampled down-core with overlapping 7 cm long core-surface scrape samples throughout the top 27 m. Each sample represents a time interval of about 1000 yr. This report describes one of these records (68 I A) spanning the last 400 kyr in the top 27 m based on the analysis of 340 individual samples.

Results presented here differ from those of Schrader and Sorknes (1990) in defining an improved transfer function, using a complete sample set, applying a corrected stratigraphic interpretation to Hole 681 A, and from Schrader (1992a) by extending the record from 160 to 400 kyr. The new correlation between the 6taP stratigraphy of Hole 680B and the shallower Hole 681A is based on organic carbon, ~itsO variations, occurrences of unique diatom assemblages and assumes a 2.75 m loss of surficial material in the top of Hole 681A (Schrader, 1992a,b)o Marine planktonic diatoms are the dominating phytoplankton group in the early stages of freshly upweiled waters (Blasco, 1971). They are excellent indicators of the successional stages of an aging upwelling system and their presence in marine

241

COASTAL UPWELLING AND ATMOSPHERIC CO2 CHANGES

sediments is useful as a primary productivity tracer (Schuette and Schrader, 1981). Diatom species were counted in the core samples and the composition of their assemblages was utilized to define a transfer function (PDU #3, Peru Diatom Upwelling; Table 1) relating the distribution of diatom assemblages from surface sediment samples (Schuette and Schrader, 1979; Schrader and Sorknes, 199 !) to a 10 year averaged primary production map (Zuta and Guill6n, 1970; Schrader, 1992a). The new transfer function improved the standard error of estimate from 25 m as defined in Schrader and Sorknes (1991)--to 19 gC/m2/yr. Transfer function PDU #3 formed the basis for calculation of primary production variations over the top 27 m (Fig. 2) of ODP Leg 112 Site 681A. This depth series is unfiltered ~,.ndcontains intervals of uncertainty (incomplete core recovery) at the top (0-0.63 m), and at the core breaks at 6.5, 16 and 25.5 m caused by hydraulic piston coring operations. These intervals are marked by the upward pointing arrows in Fig. 2. The production fluctuations based on diatom tracers as presented here are matched by the total organic carbon variations (Heinze, 1990; Wefer et al., 1990). The downocore distribution of diatom assem-

blages, the levels of last and mass occurrence of certain diatom species, the sequence of sedimentological units, the shape of the organic carbon and 180 curves were used to correlate the 681A record to the nearby 680B record. An oxygen isotope stratigraphy was proposed for the latter site (Heinze, 1990; Wefer et al., 1990) using 61aO of the benthic foraminifera Bolivina seminuda. This correlation and the placement of oxygen isotope stage boundary ages (Martinson et al., 1987) were used to define an age-depth model for Site 68 I A (Table 2; Fig. 3). Using the age model of Fig. 3 the depth scale is converted into a time scale (Fig. 4) sampled at evenly spaced time intervals of 1.05 kyr. The "Specmap stack" of relative global ice volume (lmbrie et al., 1984) (Fig. 4, bottom) serves as a stratigraphic reference and shows the placement of oxygen isotope stage boundaries, their numbers and the general cyclicity of glacials and interglacials. The time series of primary production (Fig. 4; Table 3) displays a record of primary production variation off central Peru with a mean of 209 (minimum 129, maximum 275) gC/m2/yr. Large deviations from the mean of >20% occurred during times of increased global ice volume

TABLE 1 PDU #3 is based on the distribution 5 marine planktonic diatom factors in 48 surface sediment samples (Schrader and Sorknes, 1990) and their relationship to averaged annual primaryproduction Variable name

Regression coefficient

Std. error of regressioncoefficient

Computed T-value

Delphineis karstenii A,zpeitia nodulifer Actinocyclus ehrenbergii Skeletonema costatum Cycloteila spp.

0.73416 - 143.51840 157.03180 81.35053 51.!0340

12.98621 13.67018 14.09319 14.49537 !2.40674

- 0.057 - 10.499 11.142 5.612 4.I19

Intercept Mean absolute value of residuals Standard deviation of absolute value of residuals Maximumabsolute value Minimumabsolute value

155.23290 13.7934 9.6292 37.6016 0.5430

The statistics for PDU//3 (productionvaluesin gC/m2/yr)are: Multiplecorrelation coefficient:0.971. Multiplecorr. coeff, adjusted for degrees freedom:0.969. F-value for analysis of variance: 140.973. Standard error of estimate: 17.922. Std. error of estimate adjusted for degrees of freedom: 18.737.

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Depth (mbsf) 681A Fig. 2. Calculated primary production (gC/m2/yr) based on marine planktonic diatom assemblages and PDU #3 transfer function versus depth in 681A. Black arrows along x-axis indicate core breaks and stippled line represents present day primary production over Site 68 ! A.

TABLE 2 Ages of ODP Leg !!2, Site 681A core levels in kyr. Ages are interpolated by correlating Site 681A to the nearby Site 680B and adopting the benthic oxygen isotope stratigraphy of Site 680B (Wefer et al., 1990; Heinze, 1990) Depth mbsf

Age kyr

Depth mbsf

Age kyr

Depth mbsf

Age kyr

0 ! 2 3 4 5 6 7 8 9 !0

12.5 27.5 40 52.5 65 80 92.5 105 112,5 ! 20 140

10.5 11 12 12,5 13.25 14 14.95 15.75 16 !7 17.5

i50 160 175 185 197.5 215 225 250 260 272.5 285

! 8.5 19.5

305 340

between 15-25 and 255-300 kyr (Fig. 4). Decreases of over 20% occurred during times with global ice volume decreases at !10-135, 170-180, 210-220 and 310-330 kyr. The time series contains highs and lows in primary production during both glacial and interglacials except during oxygen isotope stage be, which had consistently low values. Due to sampling and recovery constraints caused by the hydraulic piston coring, Site 681A did not

recover sediments of the last interglacial and the present. Because of the similarity of the Peruvian primary production time series and the time series of pCO 2 trapped in air bubbles from the Vostok ice core (Barnola et al., 1987), I have used the two records of the last 160 kyr to write a regression equation (Table 4) and used this equation to calculate atmospheric pCOz variations over the last 400 kyr (Fig. 5, top). The similarity of the two records is good except for the interval around 40 kyr. The Peruvian predicted atmospheric p C O 2 is also in good agreement with the A613C time series from the eastern Equatorial Pacific core V19-30 (Shackleton and Pisias, 1985) (compare Fig. 5, top and bottom: linear regression r-0.65) and with the shorter records from the northwest African upwelling system (Sarnthein et al., 1987, 1988). The simultaneous variation in both the blue water (oceanic; Berger and Keir, 1984; Sarnthein et ai., 1987; Mix, 1989) and the green water (neritic) biological pump over wide areas of the low to mid latitude oceans and in coastal upwelling areas of the eastern boundary current systems supports the hypothesis of Sarnthein et al. (1987) of their control by the meridional wind systems related to the changes of middle high latitude sea ice and associated oceanic temperature gradients.

COASTALUPWELLINGAND ATMOSPHERICCO2 CHANGES

243

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Depth (mbsf) 681A Fig. 3. Age-depth relation of the top 25 m at Site 681A with average sedimentation rates o f 7 c m / y r 3 over the interval 0 - 1 0 m b s f and 5 c m / y r 3 over the interval 15-25 mbsf. This relationship was used as the age-depth model to convert depth into time. Depth is in meters below the scafloor ( m b s f ) .

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Age (kyr) 681A Fig. 4. Calculated primary production (gC/mZ/yr) over the last 400 kyr at Site 681A sampled at even age increments of !.05 kyr. The "Specmap stack" of lmbrie et al. (1984) representing global ice volume and sequence of glacial-interglacial stages (Martinson et al., 1987) is plotted at the bottom. Numbering and arrows along x-axis represent oxygen isotope stages and their boundaries.

The "true" variation in primary production of coastal upweiling areas is best recorded in sediment sections retrieved from locations close to the actual coastal upwelling process. Due to the large "new production" (Dugdale and Goering, 1967) of organic carbon-containing particles that settle through the water column and due to their partial recycling, a well developed shallow-water oxygen

minimum zone bathes the slope and outer shelf, resulting in high sedimentation rates and deposition of sediments that are minimally bioturbated. These sections represent an unprecedented record of oceanographic change if their stratigraphy can be well constrained. Off central Peru and off Namibia this type of geological record is preserved even in water depth of less than 200 m. Coastal

244

H. SCHRADER

TABLE 3 Estimated primary production at ODP Leg 112, Site 681A in gC/m2/yr. The 7-cm long samples are listed only wi2h their midpoints, The age-depth model proposed here (see Table 2) can be used to convert the depth scale into a time scale Depth

Product.

Depth

Product.

Depth

Product.

Depth

Product.

Depth

Product.

0.63 0.70 0.78 0.84 0.91 0.99 1,06 1.14 1.20 1.28 !.35 i.43 !.55 !.63 !.71 !.77 i.86 1.94 2.01 2. ! 2 2.23 2.30 2.38 2.45 2.52 2.60 2.68 2.75 2.83 2.91 2.97 3,04 3,1 ! 3.19 3,27 3,34 3.41 3.49 3.57 3.64 3,71 3,78 3.85 3.94 4.01 4.09 4,13 4.25 4,32 4.39 4.46 4.54

258.62 261.95 265.11 253.15 250.09 275.39 188.73 201.75 237.86 236,43 240,74 231.96 233.82 226.94 235.23 238.66 230.83 227.89 189.85 224.97 192.22 196.24 227.78 239.28 209,63 232.48 244.71 232.64 248.30 233,88 239.16 234.63 227,28 231.74 233,63 233,27 234.07 232,54 232.54 232.24 232.01 232,21 232.54 23 ! .8 ! 250.20 194.64 183.94 198,73 192.66 2 ! 5, 58 207.47 206.25

5,82 5.89 5.96 6,04 6.11 6.18 6.27 6.90 6.98 7.05 7.1 i 7.20 7.27 7.35 7.42 7.49 7,57 7.64 7.71 7.79 7.86 7.94 8.04 8. i ! 8.18 8.25 8.32 8,39 8.40 8.46 8.53 8,60 8.67 8.74 8,81 8,89 8.97 9.05 9.12 9.20 9.27 9.34 9.42 9.54 9.62 9.69 9.77 9.84 9.91 9.99 10.06 I 0.14

216.53 182.68 202.99 187.19 196.19 189.15 198.62 250.25 249.35 252.83 218.72 242.21 241.27 175.10 170.99 239.76 205.63 2 ! 2.8 ! 185.49 ! 76.14 154.87 166.86 ! 70.68 ! 49.43 160.42 157.78 147.81 ! 60.36 160.52 160.94 157.76 163.06 143.68 145.49 165.28 147.93 151.66 152.34 154.22 160.64 154.53 165.69 169.1 i 174.51 162.74 174.56 186.19 217.92 199.75 189.29 202.94 ! 95.99

1 !.42 ! !.49 1 !.56 ! 1.63 1!.71 1!.78 11.86 1 !.93 ! 2.0 ! 12.08 12.16 12.23 12.30 12.37 12.44 12.55 12.62 12.69 12.77 ! 2.84 12.91 12.95 i 3.06 ! 3.13 13.21 13.28 13.35 ! 3.42 13.50 13.57 13.65 13.72 13.80 13.87 13.93 13.98 14.05 14.12 14.19 14.26 14.34 14.41 14.49 14.56 14.64 14.71 14.79 14.87 14.94 15.0 ! 15.09 15. i 6

194.65 193.72 195.71 187.51 209.67 193.53 182.93 184.57 ! 89.81 196.82 213.56 188.61 224.59 228.57 223.12 252.71 218.69 210. 32 209.1 ! 244.02 232.98 227.81 224.88 2 ! 3.08 221,04 222.38 216.99 220.00 192.40 235.35 197.27 229.83 209.24 200.22 193.97 164.90 218.57 179.87 202.82 238.28 251.16 188.09 168.78 238.85 242.58 226.20 170.88 235.00 245.51 248.63 204.94 204.54

16.71 16.79 16.86 16.94 17.01 17.08 17.15 17.22 i 7.30 17.38 17.45 17.54 17.61 17.69 17.77 17.84 17.91 i 7.99 18.06 i 8. ! 3 18.20 18.28 i 8.35 ! 8.42 18.49 18.57 18.64 !8 . 7 1 18.79 18.86 18.93 19.06 19.13 19.20 19.28 19.35 19.42 19.50 19.57 19.64 19.72 19.79 19.86 19.94 20.01 20.09 20.16 20.23 20.30 20.38 20.45 20.54

256.83 272.75 275.68 252.86 270.83 265.83 278.70 272.74 264.94 260.16 265.33 242.90 250.18 255.93 255.54 254.37 241.19 260.73 253.16 248.85 248.50 259.16 263.19 255.20 250.83 265.41 249.61 247.95 266.20 238.38 189.91 184.82 231.97 150.34 197.69 215.83 159.30 129.30 168.15 174.82 166.49 215.45 243.04 239.00 151.30 158.52 154.29 232.17 232.44 168.24 136.26 177.94

21.77 21.84 21.92 21.97 22.04 22.1 ! 22.19 22.27 22.34 22.41 22.48 22.55 22.63 22.70 22.77 22.84 22.92 22.99 23.06 23. ! 3 23.21 23.28 23.36 23.43 23.61 23.68 23.75 23.83 23.90 23.97 24.05 24.50 24.57 24.65 24.72 24.79 24.86 24.93 24.97 25.04 25.12 25.71 25.78 25.86 25.93 26.00 26.08 26.15 26.22 26.28 26.36 26.44

237.29 265.70 180.93 242.71 155.90 152.34 194.09 167.24 185.51 178.83 170.28 164.39 172.05 163.36 177.46 167.55 180.37 170.40 196.42 154.53 156.87 171.96 ! 53.24 157.66 166.05 197.77 155.49 159.55 167.64 156.62 233.95 188.95 170.27 160.24 164.31 148.80 157.53 192.50 192.61 158.84 202.17 166.85 208.59 207.68 227.85 203.1 ! 175.03 166.30 145.40 ! 79.94 184.59 202.52

COASTAL UPWELLING AND ATMOSPHERIC COz CHANGES

245

(continued)

TABLE 3 Depth

Product.

Depth

Product.

Depth

Product.

Depth

Product.

Depth

Product.

4.61 4.69 4.74 4.84 4.91 4.99 5.06 5.14 5.22 5.29 5.37 5.45 5.52 5.59 5.67 5.74

196.78 195.87 201.66 188.84 224.94 226.66 206.75 21 !.67 193.42 185.98 194.75 218.51 213.65 246. ! 5 235.67 240.21

10.21 10.29 10.36 10.44 10.52 10.59 10.66 10.73 10.81 10.88 10.95 11.04 ! 1.12 1I. 19 1!.26 11.34

200.06 193.45 194.34 228.27 221.38 188.11 216.96 218.33 223.87 238.46 200.83 229.51 200.41 205.79 199.49 191.45

15.23 15.30 15.32 15.46 15.54 15.61 15.69 15.76 15.84 15.90 15.98 16.05 16.42 16.49 16.56 16.64

242.70 ! 88.59 199.35 209.09 218.21 208.45 238.54 212.59 220.97 211.20 223.32 227.44 272.44 232.40 245.93 239.86

20.62 20.69 20.76 20.84 20.91 20.98 21.05 21.13 21.20 21.28 21.35 21.42 21.49 2 ! .56 21.63 21.70

211.21 206.42 226.30 123.18 227.02 238.40 242.20 228.73 155.66 216.95 219.02 229.84 236.40 235.43 231.96 238.05

26.51 26.58 26.65 26.73 26.80 26.87 26.95 27.04 27.1 ! 27.19 27.24 27.34 27.41 27.48 27.56 27.63

179.68 188. ! 8 233.51 200.95 205.88 208.33 203.06 189.76 191.60 178.80 180.50 204.12 242.74 249.26 180.16 163.30

TABLE 4 Statistics of regression equation of Vostok CO2 (Barnola et ai., 1987) and Peruvian Site 681A calculated primary production over the last 160 kyr Variable Vostok CO2 mean = 223.6; standard deviation = 26.8 Vari:~ble 681A product, mean= 209.6; standard deviation= 29.6 Sum of squares reduced 48598.67 Proportion reduced 0.504 Multiple correlation coefficient 0.71 Multiple correlation coefficient adjusted for 0.71 degrees of freedom F-value for analysis of variance 135.24 Standard error of estimate 18.96 Standard error of estimate adjusted for degrees 18.96 of freedom Regression coefficient Intercept

- 0.644 358.53

upwelling areas were and are storage areas for huge quantities of organic carbon regardless of sea-level status. A 120 m drop in sea ievel during the Last Glacial Maximum (LGM) would place Site 681A in a water depth of 30 m; even at this shallow water depth fine grained autochthonous sediments rich in organic carbon accumulated during oxygen isotope stages 2, 6, 8 and 10. The reasons for excluding sea-level variations as the cause for controlling the shape of the primary production curve are the following: (1) Delicate diatom valves are present in sediments of both low and high sea-level stands, as are enrichments of

robust valves. (2) Production changes in stratigraphically well constrained (Shackleton et al., 1990) sediments of Site 677, off Ecuador, show similar timing of increased and decreased production using marine diatoms as productivity tracers (Schrader, unpubl, data). The high accumulation of organic carbon-rich sediments within "shallow" water shelf and upper slope environments during periods of lowered sea level indicates that these carbon sinks were active during both glacials and interglacials. Average sediment organic carbon values in central Peruvian upwelling facies are 4.1 wt% for shelf sites (Sites 680 and 681) and 2.2 wt% for upper slope sites (Site 686: Heinze, 1990; Wefer et al., 1990) compared with typical organic carbon contents of deep-sea sediments of 0.3 wt%. The combined open and coastal Pacific Ocean constitutes 41% of present global ocean production (Berger et al., 1987, 1989); this 41% can be further subdivided into 26% (of total) representing open ocean and 15°6 representing coastal Pacific production. The Pacific coastal upwelling areas within the eastern boundary current systems account for more than half of the coastal production. Since the coastal upwelling areas off Peru are the strongest, they are a major sink for organic carbon. Presently around 90 x 106 tC/yr are being fixed through biological activity along a 300 mile offshore band between 4 ° and 24°S. If on the

H. SCHRADER

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Age (kyr) V 19-30 Fig. 5. Upper part: Predicted atmospheric pCO2 ( p p m ) over the last 400 kyr o f Site 680A and c o m p a r i s o n to the Vostok ice airbubble atmospheric p C O z record (Barnola et al., 1987) o f the last 160 kyr. L o w e r part: Predicted a t m o s p h e r i c C O t (note scale increasing towards the b o t t o m ) variations ( p p m ) over the last 350 kyr based o n A f ' a C o f benthic a n d p l a n k t o n i c foraminifera o f the eastern Equatorial Pacific core V!9-30 (Shackleton a n d Pisias, 1985).

average 10% of organic carbon fixed in the photic zone gets incorporated into the sediments (Berger et al., 1989) and is preserved in the sedimentary record then 9 x l06 tC/yr is removed from the Peruvian coastal surface waters; this in turn will have a fundamental influence on the concentration of atmospheric pCO2. Therefore the key areas for controlling atmospheric pCO 2 concentration and its decreases during glaciais and increases during interglacials may be found in the mid to low coastal upweiling areas within the eastern boundary current systems (compare this record with that from northwest Africa; Suess and Miiiler, 1980)

and not necessarily in the southern high latitude (Miiller et al., 1983). The shallow water areas underlying the eastern boundary current systems are decoupled from the deep ocean areas and surface water production changes recorded in these sh~!!ow sedimentary environments might not influence deep water chemistry, including alkalinity (Broecker and Peng, !989). The separation of nutrient poor waters in the Pacific (below 2500 m), northern Indian, and the north Atlantic (below 700 m) (Duplessy et ai., 1988; Kallel et al., 1988) during glacials may be a result of the stripping effect due to largely increased production in the

COASTALUPWELLINGAND ATMOSPHERICCO, CHANGES

coastal upwelling zones that are fed by intermediate waters. ~;~. Acknowledgements Samples from ODP Leg ! 12 were made available through the Ocean Drilling Program and its funding agencies; Peruvian surface sediment samples were provided by the core repository of the College of Oceanography, Oregon State University, Corvallis, Oregon, USA (funded through grants from ONR and NSF). Comments by M. Paetzel, T. Schrader, N. Swanberg, W.H. Berger and W.W. Hay helped to improve this paper. Financial support from the Norwegian Research Council for Science and Humanities (NAVF) within the POC (Predicting Ocean Climate) and ODP (Ocean Drilling Program) programs is acknowledged. This is POC contribution No. 49. References Barber, R.T. and Smith, R.L., 198 l. Coastal upwelling systems. !~l: A.R. Longhurst (Editor), Analyses of Marine Ecosystems. Academic Press, New York, pp. 31-68. Barnola, J.M., Raynaud, D., Korotkevich, Y.S. and Lorius, C., 1987. Vostok ice core provides 160,000-year record of atmospheric CO2. Nature, 329: 408-414. Berger, W.H. and Keir, R.S., 1984. Giacial-Holocene changes in atmospheric CO2 and the deep-sea record. In: J.E. Hansen and T. Takahashi (Editors), Climate Processes and Climate Sensitivity. Geophys. Monogr., 29: 337-351. Berger, W.H. and Vincent, E., 1986. Deep-sea carbonates: reading the carbon isotope signal. Geol. Rundsch., 75: 249-269. Berger, W.H., Fischer, K., Lai, C. and Wu, G., 1987. Ocean productivity and organic carbon flux. I. Overview and maps of primary production and export production. Univ. California, Scrips Inst. Oceanogr., La Jolla, Reference 87-30, 67 pp. Berger, W.H., Smetacek, V. and Wefer, G. (Editors), 1989. Productivity of the Ocean. Present and Past. Wiley, Chichester, UK, 471 pp. Blasco, D., 1971. Composition and distribution of phytoplankton in the upwelling off the coast of Peru. Invest. Pesq. Peru, 35:62-112. Broecker, W.S. and Peng, T.-H., 1989. The cause of the glacial to interglacial atmospheric CO2 change: A polar alkalinity hypothesis. Global Biogeochem. Cycles, 3: 215-239. Dugdale, R.C. and Goering, J.J., 1967. Uptake and regenerated forms of nitrogen in primary productivity. Limnol. Oceanogr., 12: 196-206. Dunbar, P..B., Marty, R.C. and Baker, P., 1990. Cenozoic marine sedimentation in the Sechura and Pisco basins. Paleoceanogr., Paleoclimatol., Paleoecol., 77: 215-225.

247 Duplessy, J.C., Shackleton, N.J., Fairbanks, R., Labeyrie, L., Oppo, D. and Kallel, N., 1988. Deep water source variations during the last climatic cycle and their impact on global deep-water circulation. Paleoceanogr., 3: 343-360. Heinze, P., 1990. Das Auftrieb°geschehen vor Peru im Sp~itquart/ir: Ocean Drilling Program (ODP) Forschungsfahrt Nr. 112: Bohrungen 679D, 680B, 681B, 686B. Ph.D. Thesis, Univ. Bremen. lmbrie, J., Hays, J.D., Martinson, D.G., Mclntyre, A., Mix, A.C., Morley, 3.J., Pisias, N.G., Prell, W.L. and Shackleton, N.J., 1984. The orbital theory of Pleistocene climate: Support from a revised chronology of the marine ~lso record. In: A.L. Berger, J. Imbrie, J. Hays, G. Kukla and B. Salzman (Editors), Milankovitch and Climate. (NATO AS! Ser. C, 126.) Reidel, Dordrecht, I, pp. 269-305. Kallel, N., Labeyrie, L.D., Juillet-Leclerc, A. and Duplessy, J.C., 1988. A deep hydrological front between intermediate and deep-water masses in the Indian Ocean. Nature, 333: 651-655. Martinson, D.G., Pisias, N.G., Hays, J.D., lmbrie, J., Moore, T.C., Jr. and Shackleton, N.J., 1987. Age dating and the orbital theory of the ice ages: Development of a high resolution 0 to 300,000 year chronostratigraphy. Quat. Res., 27: !-29. M~,x, A.C., 1989. Pleistocene paleoproductivity: Evidence from organic carbon and foraminiferal species. In: W.H. Berger, V. Smetacek and G. Wefer (Editors), Productivity of the Ocean: Past arid Present. Wiley, Chichester, UK, pp. 225-269. Mfiller, P., Erlenkeuser, H. and Von Grafenstein, R., 1983. Glacial-interglacial cycles in ocean productivity inferred from organic carbon contents in eastern Atlantic sediment cores. In: J. Thiede and E. Suess (Editors), Coastal Upwelling, Its Sediment Record, Part B: Sedimentary Records of Ancient Coastal Upwelling. (NATO Conf. Set., 10B.) Plenum, New York, pp. 365-398. Sarnthein, M., Winn, K. and Zahn, R., 1987. Paleoproductivity of oceanic upwelling and the effect on atmospheric CO2 and climate change during deglaciation times. In: W.H. Berger and L.D. Labeyrie (Editors), Abrupt Climatic Change. Reidei, Dordrecht, pp. 31 !-337. Sarnthein, M., Winn, K., Duplessy0 J.-C. and Fontugne, M.R., 1988. Global variations of surface ocean productivity in low and mid latitudes: Influence on CO, reservoirs of the deep ocean and atmosphere during the last 21,000 years. Paleoceanography, 3: 361-399. Schrader, H., 1992a. Peruvian coastal primary paleoproductivity during the last 200,000 years. In: C. Summerhayes, W. Prell and K. Emeis (Editors), Evolution of Upwelling Systems Since the Early Miocene. Geol. Soc. London, in press. Schrader, H., 1992b. Comparison of Quaternary coastal upwelling proxies off Central Peru. In: G.J. van der Zwaan, F.J. Jorissen and W.J. Zachariasse (Editors), Approaches to Paleoproductivity Reconstructions. Mar. Micropaleontol., 19: 29-47.

248 Schrader, H. and Sorknes, R., 1991. Peruvian coastal upwelling: Late Quaternary productivity changes revealed by diatoms. Mar. Geol., 97: 233-249. Schuette, G. and Schrader, H., 1979. Diatom taphocoenoses in the coastal upwelling area off Western South America. Nova Hedwigia, lkihefte, 64: 359-378. Schuette, G. and Schrader, H., 1981. Diatoms in surface sediments: A reflection of coastal upweiling. In: F.A. Richards (Editor), Coastal Upwelling. Am. Geophys. Union, Washington, pp. 372-380. Shackleton, N.J., Berger, A. and Peltier, W.R., 1990. An alternative astronomical calibration of the lower Pleistocene timescale based on ODP Site 677. Trans. R. Soc. Edinburgh Earth Sci., 81: 251-261. Shackleton, N.J. and Pisias, N.G., 1985. Atmospheric carbon dioxide, orbital forcing, and climate. In: E.T. Sundquist and W.S. Broecker (Editors), The Carbon Cycle and Atmospheric

H. SCHRADER

CO2: Natural Variations Archean to Present. Am. Geophys. Union, Washington, pp. 303-317 Suess, E. and MfiUer, P., 1980. Production, sedimentation rate and sedimentary organic matter in the oceans. II Elemental fractionation. Biogeochemie de la mati6re organique ~tl'mterface eau-s~liment marin. Colloq. Int. CNRS, 293: 17-26. Suess, E., Von Huene, R. Emeis, K. and shipboard scientific party, 1988. Proc. ODP, Init. Rep., 112, 1015 pp. Suess, E., Yon Huene, R. and Emeis, K., 1990. Proc. ODP, Sci. Results, ! 12, 738 pp. Wefer G., Heinze, P. and Suess, E., 1990. Stratigraphy and sedimentation rates from oxygen isotope composition, organic carbon content, and grain size distribution at the Peru upwelling region: Holes 680B and 686B. In: Proc. ODP, Sci. Results, 112: 355-367. Zuta, S. and Guill~n, O., 1970. Oceanografia de las aguas costeras del Peru. Bol. Inst. del Mar del Peru, 2: 161-323.