10. CRETACEOUS AND EARLY TERTIARY FORAMINIFERS FROM DEEP SEA DRILLING PROJECT LEG 62 SITES IN THE CENTRAL PACIFIC1 Anne Boersma, Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York INTRODUCTION Table 1. Geographic position of DSDP Leg 62 sites in the central Pacific today. During DSDP Leg 62, foraminifers were recovered from four holes in the central North Pacific. At Site Water Depth 463, in the Mid-Pacific Mountains (21°21'N, 174° Leg Site Latitude Longitude (m) 40'E; water depth 2525 m), the Cretaceous section in- cluded Aptian-Albian to Maastrichtian sediments. Pa- 6 47 32°26'N 157°42'E 2689 leogene faunas occurred in a mixed zone in three cores 6 45 25°15'N 198°30'E 4508 6 44 19°18'N 169°00'E 1478 from strata unconformably overlying the Cretaceous. 32 305 32°13'N 157°51'E 2903 Recovery was very poor at Site 464 (39°51'N, 173° 32 310 36°52'N 176°54'E 3516 53'E; water depth 4637 m), on the northern flank of 32 313 20°10'N 170°57'E 3484 Hess Rise. Twenty-four cores of Cretaceous material 17 171 19°07'N 169°27'E 2295 encompassed the Cenomanian-Albian. Site 465 (Hole 20 200 12°50'N 156°46'E 1879 20 202 12°48'N 156°57'E 1515 465A) on southern Hess Rise (33°49'N, 178°55'E) was 30 288 5°58'N 161°49'E 3000 drilled at a depth of 2161 meters. The Cretaceous sec- 30 289 0°29'N 158°30'E 2206 tion includes upper Albian to uppermost Maastrichtian. 6 51 33°28'N 153°24'E 5981 The Cretaceous/Tertiary boundary was recovered in 17 167 7°04'N 176°49'E 3176 20 199 13°30'N 156°10'E 6100 Hole 465A, and the combined Paleocene sections from 62 463 21°21'N 174°40'E 2525 both sites spanned all zones of the Paleocene. A mixed 62 464 39°51'N 173°53'E 4637 zone of Paleogene sediments overlies the Paleocene at 62 465 33°49'N 178°55'E 2161 Site 465. Because of the abundance of chert, only core 62 466 34°11'N 179°15'E 2665 catchers were recovered in many instances. Poor recov- ery characterized the Cretaceous section also at Site 466, on southern Hess Rise (34°H'N, 179° 15'E; water BIOSTRATIGRAPHY depth of 2665 m). The Cretaceous section includes 24 cores, of which half contain only core catchers; only the Site 463 Campanian was successfully cored. Four overlying Site 463 was continuously cored, and sediments were cores contain mixed Paleogene and Cretaceous mate- recovered from the Aptian-Albian to the Maastrichtian. rials, thus representing the commonly occurring Paleo- Significant hiatuses include the Coniacian-Campanian, gene "mixed zone" of the central Pacific (Table 1; Figs. and the latest Maastrichtian. 1 and 2). Both planktonic and benthic foraminifers were pres- Preservation ent in nearly every sample younger than Aptian. Pres- No foraminifers were found in samples below Core ervation varied from generally poor in most Albian 66, presumably because of the very poor preservation of samples at each site to very good in most of the Campa- the material. Late Aptian-Albian faunas were only oc- nian-Maastrichtian section. Paleogene sequences were casionally preserved; foraminifers are uncommon in the generally well preserved, except in the mixed zone, radiolarian oozes. Recognizable foraminifers are tiny where dissolution and recrystallization were common. and recrystallized. Middle to late Albian (Cores 55-48) faunas are slightly better preserved, but still recrystal- METHODS lized, and apertures are often obscured. Preservation Cretaceous planktonic foraminifers were zoned according to the improves in the Cenomanian (Cores 46-40), although zonation and time scale of van Hinte (1976). Faunas were surveyed, intense dissolution is present in Core 43. Preservation is selected species were identified, and relative abundances of those species are tabulated in Figures 3 and 4. Because the author is not a better in the Turonian, although foraminifers are very specialist in Cretaceous planktonics, not all species could be iden- rare in some intervals (Cores 36 and 37). Moderate tified; faunal lists, therefore, are not inclusive. preservation characterizes most of the upper Turonian Paleogene planktonic foraminifers were zoned according to the and Coniacian, until in Core 30 foraminifers are entirely zonation and time scale of Hardenbol and Berggren (1978). Relative recrystallized and cemented together. Campanian sedi- abundances of Paleocene species are tabulated in Figure 5. ments are generally well-preserved, except for intervals of moderate to intense dissolution accompanied by Initial Reports of the Deep Sea Drilling Project, Volume 62. chert in Cores 24, 23, 22, and one section of 21. In some 377 A. BOERSMA 10° 170° 180° 170° 160° Figure 1. Locations of sites drilled on DSDP Leg 62 in the central Pacific. faunas, most of the large specimens have been removed Slightly more-diverse faunas allow recognition of the by dissolution. Good preservation characterizes the Rotalipora ticinensis-Planomalina buxtorfi Zone (52 to Maastrichtian, except where dissolution has altered 50,CC) by the overlap of the nominate taxa. Ticinella faunas in sections of Cores 18,17, 16, 12, 11, and 9. Re- species become larger and more diverse in this zone, and crystallization of foraminifers occur in two isolated in- Planomalina buxtorfi is large and abundant at one level. stances in Core 10 and in one section of Core 13. The first appearance of Rotalipora apenninica, ac- companied by Rotalipora evoluta, before the appear- Foraminifer Faunas ance of Rotalipora gandolfi, despite the absence of P. Aptian-Albian faunas (66-2 to 53,CC) have only buxtorfi, suggests that Cores 49,CC to 48-2 belong to been roughly zoned, since the poor preservation and in- the latest Albian P. buxtorfi-R. apenninica Zone. Ro- frequent faunas make zonal assignation difficult. The talipora apenninica and Praeglobotruncana stephani are co-occurrence of Ticinella bejaouaensis and Hedber- common along with H. planispira and Hedbergella del- gella planispira in Cores 64 and 65 suggests that the rioensis, but Ticinella spp. are less frequent. Clavihed- samples are located in the uppermost T. bejaouaensis bergella was not seen; Shackoina occurs only in 48,CC. Zone and may be Albian. The presence of Ticinella The first appearance of Rotalipora gandolfi (48-1) primula in 56,CC and Ticinella breggiensis in 53,CC marks the base of the Rotalipora gandolfi-Rotalipora suggests subdivision of this interval into two middle Al- greenhornensis Zone (48-1 to 44,CC). Rotaliporids, P. bian zones, but faunas are not well enough preserved. stephani and the hedbergellids occur commonly. The 378 SERIES PLANKTONIC PERIOD STAGE ZONE SITE 463 SITE 464 SITE 465* SITE 466 SERIES ZONE 465 465A 50- 55H 2-3 P5 P5 (3-1) 3-1 3-1 top P4 1-1 (3-2 to 5-1) 1-1 P4 P3 (5-2 to 7.CC) 60- P2 r/jrsr/sz 5-1 1-1 80 cm P1 5-1 1-1 120 cm G. eugubina× Ga. mayaroensis 3-3 to 3.CC 6-5 1.CC 8-2 to 13-1 G. contusa 4 to 8,CC P3 G. stuarti 13-2 to 15-2 G. gansseri 9-3 to 12,CC G. scutilla 15-3 to 21-1 70- ?. ca I carat a 15-1 to 20-2 1 60- Hi G. subspinosa P2 G. stuartiformis 7.CC 12.CC G. elevata 29-3 to 26-1 8.CC 3-2 15 cm 3-2 35 cm .£80- G• concavata— 20,CCto25,CC 16-3to21,CC P1 elevata G. sigali—concavata 26-2 to 26-5 ill 24,CC to 3-3 G. renzi—G. sigali 27.CC to 30,CC 28.CC ill 3-3 40 cm "G" helvetica 33-1 to 34-3 3-3 138 cm 90- 65 H. lehmani 34,CCto39,CC 1 R. cushmani 40,CC to 43-5 > σ R. gandolfi—reicheli m R. gandolfi — > greenhornensis 44,CC to 48-1 26-1 to 27.CC r 100- P. bu×torfi—R. apenn. 48-2 to 49.CC 13,CCto27,CC 28-1 to 40-1 R. ticinensis- P. bu×t. 50,CCto52,CC T. breggiensis 53,CC T. praeticinensis T. bejao. - T. primula T. bejaouaensis — G/• gyr. 67,CC Gl. ferr. — T. bejao. Aptian 110- * Holes 465 (parenthesis) and 465A Figure 2. Biostratigraphic summary of Leg 62 sites according to planktonic foraminifers. Planktonic-foraminifer zonation and time scale for the Cretaceous by van Hinte (1976); Paleogene time scale, by Hardenbol and Berggren (1978). Core levels within a zone shown beside the appropriate zone; hiatuses are hachured. A. BOERSMA INTER- VAL ZONE :: Gtr. confuse Gtr. stuarti - Gtr. gansseri ETCHED ETCHED Gtr '• • t: scutilla Gtr. calcarata - to Gtr. subspinosa HERT Gtr. e leva to G. cone a vat a Z< -G sigali o o o < G. renzi- G. sigali TUR F F I C C F R Figure 3. Relative abundances of selected planktonic foraminifer species at Site 463 in the Mid-Pacific Mountains. Recrystallization is indicated by darker banding; levels of significant dissolution by the lighter bands. Levels with chert, etched foraminifers, anomalously small samples, or samples containing only juveniles are indicated. Symbols: A, abundant; C, common; F, frequent; I, infrequent; R, rare. Time scale follows van Hinte (1976). appearance of R. cushmani in 43-5 marks the beginning gella lehmani Zone (39 to 34,CC). Heterohelix globu- of that Zone (43-5 to 40,CC). Rotaliporids are common losa, Dicarinella spp., and Praeglobotruncana praehel- through this interval, but only three or four species oc- vetica first occur in these faunas, which are dominated cur in any sample.