Globally synchronous extinction of the radiolarian Stylatractus universus
PDF | Through comparison of the extinction level of Stylatractus universus with the Î´O18 record in widespread high- and...
Globally synchronous extinction of the radiolarian Stylatractus universus
ABSTRACT Through comparison of the extinction level of Stylatractus universus with the 5 0 1 8 record in widespread high- and lowlatitude deep-sea cores, we show that this level is globally synchronous. It occurs in the lower one-third of the isotopic transition between isotope Stages 12 and 11. Several independent estimates of the date of this extinction converge on 410,000 ± 5,000 yr ago. This biostratigraphic datum is now well dated and is globally synchronous.
INTRODUCTION Although globally synchronous extinctions have been postulated, few have been documented, to our knowledge. If such events occur, they have great value to global correlations. Faunal extinctions have sometimes been considered less reliable than evolutionary first appearances for long-range correlations. The argument has been that for a cosmopolitan species, ecological factors causing its disappearance may have varied with time over its geographic range. Consequently, extinctions are apt to appear diachronous, whereas evolutionary first appearances that can only happen once are better stratigraphic markers (Banner and Blow, 1965). The weakness of this argument for planktonic organisms is that the evolutionary development probably occurred in a restricted region and the later, more widespread distribution occurred by migration. Although the later migration may have been rapid in geological terms, it is subject to the same kind of ecological diachronicity as are extinctions. GEOLOGY, v. 4, p. 649-652
James D. Hays L a m o n t - D o h e r t y Geological O b s e r v a t o r y of C o l u m b i a U n i v e r s i t y Palisades, N e w Y o r k 1 0 9 6 4 and t h e D e p a r t m e n t of Geological Sciences, C o l u m b i a U n i v e r s i t y New Y o r k , New Y o r k 10027
Nicholas J. Shackleton* S u b - d e p a r t m e n t o f Q u a t e r n a r y Research, C a m b r i d g e U n i v e r s i t y C a m b r i d g e , England
Clearly the value of a global stratigraphic marker must rest on a demonstration that the event is indeed synchronous. Such a demonstration is dependent upon having an independent stratigraphic marker that is itself globally synchronous. Reversals of the Earth's magnetic field produce stratigraphic markers with this property. It has previously been demonstrated through comparing the extinction levels of a number of radiolarian species with magnetic reversals recorded in deepsea sediment cores that radiolarian extinction levels of some species are regionally isochronous (Hays, 1971). However, the geographic range of none of these species was global. Furthermore, it may be argued that these extinctions were atypical, because the magnetic reversal could directly or indirectly have given rise to the extinction. A second stratigraphic indicator that can now be used to recognize globally isochronous time lines is the change in the dO18 composition of the oceans. Shackleton and Opdyke (1973) have confirmed that most of the dO18 variation recorded in the shells of fossil foraminifera in Pleistocene
deep-sea sediments reflects ocean isotope variations caused by changes of global ice volume. As a consequence, fluctuations of dO18 in deep-sea sediments are isochronous within the limits imposed by oceanic mixing (of the order of 1,000 yr) and bioturbation of the sediments. To determine the synchrony of events recorded in deep-sea sediments during the past 1 m.y., dO18 is an ideal tool providing much higher resolution than the relatively infrequent magnetic reversals. STYLATRACTUS
We demonstrate here, using the dO18 record, that a radiolarian species Stylatractus universus Hays with a global distribution in the Pliocene and first threefourths of the Pleistocene became extinct globally at almost exactly the same time, about 400,000 yr ago. S. universus has been reported from the Antarctic-subantarctic (Hays, 1965), North *Visiting Senior Research Associate, Lamont-Doherty Geological Observatory of Columbia University. 649
TABLE 1. CORE LOCATIONS AND REFERENCES TO OTHER
Pacific (Hays, 1970), and equatorial Pacific (Hays and others, 1969), and we have observed it in equatorial Atlantic and Indian Ocean cores. From these observations, it is safe to say that the geographic distribution of this species was effectively global. The studies listed above demonstrated that in all these regions Stylatractus universus became extinct in mid-Brunhes time. Johnson and Knoll (1974) estimated the age of the extinction of S. universus in equatorial Pacific cores by interpolating between the Brunhes-Matuyama boundary and the core top and compared its stratigraphic range with that of several other species used by Nigrini (1967) to zone the Quaternary Period. They suggested that the upper limit of S. universus might be diachronous between the Indian and Pacific Oceans, because its upper limit in the Pacific is below the first appearance of Buccinosphaera invaginata (Nigrini, 1967), whereas in an Indian Ocean core it disappears above the first appearance of this species. This suggested to Johnson and Knoll (1974) that there was diachronicity either in the last occurrence (extinction) of S. universus
STRATIGRAPHICAL WORK IN THEM Core
* 1 , Shackleton and Opdyke ( 1 9 7 3 ) ; 2 , Thompson and S a i t o ( 1 9 7 4 ) ; 3 , Thompson ( 1 9 7 6 ) ; 4 , G e i t z e n a u e r and o t h e r s ( 1 9 7 6 ) ; 5 , M. T h i e r s t e i n , K. G e i t z e n a u e r , B. M o l f i n o , and N. Shackleton ( i n p r e p . ) ; M o l f i n o and o t h e r s ( 1 9 7 6 ) ; 6 , S h a c k l e t o n and Opdyke ( 1 9 7 6 ) ; 7 , Opdyke and F o s t e r ( 1 9 7 0 ) ; 8 , Hays ( 1 9 7 0 ) ; 9 , Jouse ( 1 9 7 1 ) ; 10, Kent and o t h e r s ( 1 9 7 1 ) ; 11, N i n k o v i c h and Shackleton ( 1 9 7 5 ) ; 12, Hays and o t h e r s ( 1 9 7 6 ) .
or the first appearance of B. invaginata between these two oceans. OXYGEN ISOTOPE STRATIGRAPHY To determine whether the upper limit of S. universus is indeed synchronous throughout its broad geographic range, we have selected six deep-sea cores from such widely separated areas as the North Pacific, equatorial Pacific, subantarctic (Indian Ocean sector), and tropical Indian Ocean (Table 1). In these cores we have deterV20 -119 S0
mined the upper limit of S. universus and compared it to the dO18 record of all cores previously measured. The dO18 record in the six cores studied is shown in Figure 1. The techniques used to determine these values have been described by Shackleton and Opdyke (1973). The radiolarian separations were made by techniques described by Moore (1973). Counts of at least 2,000 radiolaria were made to estimate the total number on the slide. All specimens of S. universus that occurred on a slide were counted.
%o + 5.0
+ 3.0 +2.0 A A A
Figure 1. Range o f Stylatractus universus in six cores studied. Black and w h i t e bars in cores V 2 8 - 2 3 8 , V 2 8 - 2 3 9 , and V 2 0 - 1 1 9 indicate published magnetic stratigraphy data (inferred normal in remaining three cores). O x y g e n i s o t o p e records s h o w analyses o f Globigerinoides sacculifer (cores V 2 8 - 2 3 8 , V 2 8 - 2 3 9 , R C 1 4 - 3 7 ) , Uvigerina sp. ( c o r e s V 2 0 - 1 1 9 , V 1 9 - 2 8 ) , and Globigerina bulloides ( c o r e E 4 9 - 1 8 ) . Percent CaCC>3 also p l o t t e d for 1 s c o r e V 2 0 - 1 1 9 , in w h i c h 5 0 record is d i s c o n t i n u o u s d u e t o absence o f foraminifera in s e c t i o n s with very l o w C a C 0 3 . In c o r e V 2 0 - 1 1 9 , solid lines with circle e n d s = S O 1 8 , dashed line = C a C 0 3 .
N O V E M B E R 1976
The range of S. universus is plotted in Figure 1, and it is clear that its extinction occurs in all cores near the isotopic Stage 11-12 boundary. The isotopic data in core V20-119 are meager because of the absence of foraminifera except in short isolated intervals. However, the data are sufficient to indicate that sections of relatively high carbonate are associated with light isotopic values (odd-numbered isotope stages). The extinction of S. universus occurs at the base of the fifth carbonate peak, counting down from and including the Holocene. As the dO18 record is essentially continuous to Stage 6, we correlate this fifth peak with Stage 11. DETAILS OF EXTINCTION
The detailed relationships between the extinction of this species and the isotopic curves are shown in Figure 2. These figures indicate that in all cores the final decline of the species occurred across the isotopic transition between Stages 11 and 12. In the cores with higher deposition rates (cores E49-18, V19-28) that have the best resolution, the extinction appears to have occurred in the lower one-third of this transition. The duration of this transition, like the transition between the last glacial maximum (18,000 B.P.) and the hypsithermal (6,000 B.P.), probably did not exceed 12,000 yr. Therefore, this species disappeared from equatorial Pacific seas (V19-28) and the subantarctic Indian Ocean water (E49-18) within the same 4,000-yr interval. This is a conservative estimate of the degree of synchrony; examination of Figure 2 suggests an even closer similarity in the decline. For general stratigraphic work, the extinction levels in all cores studied can be considered isochronous. It should be noted that although the extinction can be located very accurately because of the relatively high abundance of S. universus immediately before its extinction, care must be taken GEOLOGY
1500 IN CORE
V28-238 11 I 12
V28-239 I 11
tOO IN CORE
400 IN CORE
300 DEPTH ÌN
400 CORE (CM)
Figure 2. Results of detailed study of disappearance of S. universus. In core RC14-37, samples at 4 9 0 , 5 0 0 , 5 1 0 , and 5 3 0 cm contained too few radiolaria to enable any significance to be attached to absence of S. universus. In core V 2 0 - 1 1 9 , dashed line = C a C 0 3 , solid line with circles = S. universus, heavy solid line = D. aquilonius.
not to confuse an earlier diminution in abundance with the final extinction. In the course of this study we have obobtained further data on one other extinction—that of Druppatractus aquilonius Hays in core V20-119—as part of a long-term objective of linking all useful Pleistocene biostratigraphic datums with the dO18 record (H. Thierstein, K. Geitzenauer, B. Molfino, and N. Shackleton, in prep.; Burckle, 1976).
The date of the extinction of Stylatractus universus has been independently estimated at 400,000 yr ago in the North Pacific (Hays and Ninkovich, 1970), at 341,000 yr ago in the equatorial Pacific (Hays and others, 1969), and at 400,000 yr ago in the Antarctic (Hays and Opdyke, 1967). Since we have now shown that the extinction occurred synchronously in these three 651
regions and elsewhere, these constitute three independent estimates of the date of the same event. Shackleton and Opdyke (1973) showed that the equatorial Pacific estimate was too low because of widely fluctuating carbonate content in the cores studied by Hays and others (1969); Shackleton and Opdyke estimated the date of the same event (the Stage 11-12 boundary) in core V28-238, from a part of the equatorial Pacific not subject to the same carbonate fluctuations, as 440,000 yr ago. The rather close agreement in these three estimates, based on the assumption of constant longterm accumulation rate between the Brunhes-Matuyama boundary 700,000 yr ago and the present in areas of widely different sediment types, suggests that the mean of the three estimates would be within about 5 percent of the true age. Hays and others (1976) have clearly detected the record of the changing obliquity of the Earth's rotational axis, and the precession of the equinoxes, on one of the cores studied here (E49-18), providing an independent astronomical confirmation of the time scale. J. Shackleton and J. Imbrie (in prep.) have extended this analysis and estimate that the date of the Stage 12-11 boundary is 410,000 astronomical yr ago, with an uncertainty of only about ±5,000 yr. We regard this figure as the best estimate of the date of Stylatractus extinction.
CONCLUSIONS The extinction of Stylatractus universus was synchronous over the whole of its wide geographic range, and the date of Stylatractus universus extinction is 410,000 ± 5,000 yr ago. REFERENCES CITED Banner, F. T., and Blow, W. H., 1 9 6 5 , Progress in t h e p l a n k t o n i c f o r a m i n i f e r a l biostratigraphy of the Neogene: N a t u r e , v. 2 0 8 , p. 1 1 6 4 - 1 1 6 6 . Burckle, L. H., 1976, Pliocene and Pleistocene d i a t o m d a t u m levels f r o m t h e equatorial Pacific: Q u a t e r n a r y Research (in press). Geitzenauer, K., Roche, M., and M c l n t y r e , A., 1976, Modern Pacific coccolith assemblages: Derivation and application to late Pleistocene p a l e o t e m p e r a t u r e analysis, in Cline, R. M., and Hays, J. D., eds., Investigation of late Q u a t e r n a r y paleoceanography and paleoclimatology: Geol. Soc. America Mem. 145, p. 4 2 3 - 4 4 8 . Hays, J. D., 1965, Radiolaria and late Tertiary and Q u a t e r n a r y history of A n t a r c t i c seas; Biology of the Antarctic Sea II: A n t a r c t i c Research, ser. 5, p. 1 2 5 - 1 8 4 . 1970, Stratigraphy and evolutionary t r e n d s of radiolaria in N o r t h Pacific deep-sea sedim e n t s , in Hays, J. D., ed., Geological investi652
gations of the North Pacific: Geol. Soc. America Mem. 126, p. 1 8 5 - 2 1 8 . 1971, E x t i n c t i o n s and reversals of the Earth's magnetic field: Geol. Soc. America Bull., v. 82, p. 2 4 3 3 - 2 4 8 8 . Hays, J. D., and Ninkovich, C., 1970, N o r t h Pacific deep-sea ash c h r o n o l o g y and age of present Aleutian underthrusting, in Hays, J. D., ed., Geological investigations of the N o r t h Pacific: Geol. Soc. America Mem. 126, p. 2 6 3 - 2 9 0 . Hays, J. D., and O p d y k e , N., 1967, A n t a r c t i c Radiolaria, magnetic reversals, and climatic change: Science, v. 158, p. 1 0 0 1 - 1 0 1 1 . Hays, J. D., Saito, T., O p d y k e , N. D., and Burckle, L. H., 1 9 6 9 , Pliocene-Pleistocene sediments of the equatorial Pacific—Their paleomagnetic, biostratigraphic, and climatic r e c o r d : Geol. Soc. America Bull., v. 80, p. 1 4 8 1 - 1 5 1 4 . Hays, J. D., Imbire, J., and S h a c k l e t o n , N. J., 1976, Variations of the Earth's orbit: Pacemaker of the ice ages: Science (in press). J o h n s o n , D. A., and Knoll, A. H., 1974, Absolute ages of Q u a t e r n a r y radiolarian d a t u m levels in the equatorial Pacific: Q u a t e r n a r y Research, v. 5, p. 9 9 - 1 1 0 . Jouse, A. P., 1971, D i a t o m s in Pleistocene sedim e n t s f r o m the n o r t h e r n Pacific ocean, in Funnell, B. M., and Riedel, W. R., eds., The micropaleontology of oceans: Cambridge, Cambridge Univ. Press, p. 4 0 7 - 4 2 1 . Kent, D., O p d y k e , N., and Ewing, M., 1 9 7 1 , Climatic change in t h e N o r t h Pacific using ice-rafted detritus as a climatic indicator: Geol. Soc. America Bull., v. 82, p. 2 7 4 1 - 2 7 5 4 . M o l f i n o , B., Thierstein, H., Geitzenauer, K., and Shackleton, N. J., 1976, The e x t i n c t i o n of P. lacunora and t h e first a p p e a r a n c e of E. huxleyi: S y n c h r o n o u s coccolith Quaternary d a t u m based u p o n oxygen isotope analysis: Geol. Soc. America Abs. with Programs, v. 8, p. 101 5. Moore, T. C., 1973, Method of r a n d o m l y distributing grains for microscopic e x a m i n a t i o n : Jour. Sed. Petrology, v. 4 3 , p. 9 0 4 - 9 0 6 . Nigrini, C. A., 1967, Radiolaria in pelagic sedim e n t s f r o m the Indian and Atlantic Oceans: California Univ. La Jolla Bull. 510, v. 11, p. 125. Ninkovich, D., and S h a c k l e t o n , N., 1 9 7 5 , Distribution, stratigraphic position and age of ash layer " L " in t h e Panama Basin region: E a r t h and Planetary Sci. Letters, v. 27, p. 2 0 - 3 4 . O p d y k e , N., and Foster, J., 1970, Paleomagnetism of cores f r o m t h e N o r t h Pacific, in Hays, J. D., ed., Geological investigation of the N o r t h Pacific: Geol. Soc. America Mem. 126, p. 8 3 - 1 1 9 . S h a c k l e t o n , N., and O p d y k e , N., 1 9 7 3 , O x y g e n isotope and paleomagnetic stratigraphy of equatorial Pacific core V 2 8 - 2 3 9 : Oxygen isotope t e m p e r a t u r e s and ice volumes on a 1 0 s and 10 year scale: Q u a t e r n a r y Research, v. 3, p. 3 9 - 5 5 . 1976, Oxygen isotope and paleomagnetic stratigraphy of Pacific core V 2 8 - 2 3 9 , late Pliocene and latest Pleistocene, in Cline, R. M., and Hays, J. D., eds., Investigation of late Q u a t e r n a r y paleoceanography and paleoclimatology: Geol. Soc. America Mem. 145, p. 4 4 9 - 4 6 4 . T h o m p s o n , P., 1976, Planktonic f o r a m i n i f e r a l distribution and progress t o w a r d s a Pleistocene equatorial Pacific transfer f u n c t i o n : J o u r . Foram. Research, v. 6, p. 2 0 8 - 2 2 7 . T h o m p s o n , P., and Saito, T., 1 9 7 4 , Pacific Pleistocene sediments: Planktonic foraminifera dissolution cycles and g e o c h r o n o l o g y : Geology, v. 2, p. 3 3 3 - 3 3 5 .
P R I N T E D IN U . S . A .
ACKNOWLEDGMENTS Reviewed by W. A. Berggren, L. Burckle, and T. Saito. Supported by National Environment Research Council Grant G R 3 / 1 7 6 2 to Nicholas Shackleton at Cambridge University, Cambridge, England, and National Science Foundation Grants G A 3 5 4 6 3 X and DES 0 1 5 7 1 to LamontDoherty Geological Observatory. Coring supported by National Science Foundation Grants DES 7 2 - 0 1 5 6 8 A 0 4 and IDO 1 9 6 2 7 , and Office of Naval Research Grant N00014-75-C-0210. We thank Alice Pesanell, w h o made counts of Stylatractus universus. Shackleton gratefully acknowledges receipt of the Lamont-Doherty Geological Observatory Senior Visiting Research Fellowship 1 9 7 4 - 1 9 7 5 . MANUSCRIPT RECEIVED AUG. 20, 1976 MANUSCRIPT ACCEPTED AUG. 26, 1 9 7 6 NOVEMBER 1 9 7 6