BIOSTRATIGRAPHY

At Site 1220, we recovered a 202-m-thick sequence of lower Miocene-uppermost Paleocene radiolarian oozes, chert, and nannofossil ooze. A nearly complete sequence of lower Miocene-lower Eocene radiolarian zones was identified and was interrupted only by a poorly recovered chert sequence in the uppermost lower Eocene and the lowermost middle Eocene. Calcareous fossils are generally poorly preserved or absent through much of the sequence. Calcareous nannofossils are sufficiently well preserved in the lowermost Miocene and Oligocene to provide a basic zonation. Planktonic foraminifers are almost entirely absent above the lower Eocene, but dissolution-resistant species allow the upper/lower Oligocene boundary to be approximated. Both planktonic foraminifers and calcareous nannofossils provide a detailed zonation of a condensed sequence of lower Eocene nannofossil oozes and chert in the basal 10 m of Site 1220. The extinction of Paleocene benthic foraminifers, the appearance of the nannofossil genus Rhomboaster, the extinction of the nannofossil genus Fasciculithus, and the presence of excursion fauna of planktonic foraminifers provide a detailed biostratigraphy of the P/E boundary in Core 199-1220B-20X. The nannofossil events occur 0.8-1.4 m above the extinction of Paleocene benthic foraminifers. The excursion fauna of planktonic foraminifers is present in sediments below the level of the benthic foraminifer extinction and immediately overlying basalt. Thus, none of these events are precisely synchronous with the benthic foraminifer extinction at this site.

Calcareous Nannofossils

Samples from Holes 1220A and 1220B were analyzed for the biostratigraphic subdivision of the sedimentary succession. Depth positions and age estimates of biostratigraphic marker events are shown in Table T2.

Cores 199-1220A-1H and 2H are barren of calcareous nannofossils (Fig. F6). Poorly preserved lowermost Miocene nannofossils are observed in samples from Core 199-1220A-3H, in which assemblages are made up by solution-resistant taxa such as discoasters (Discoaster calculosus and Discoaster deflandrei gr.), abundant specimens of Triquetrorhabdulus spp. (Triquetrorhabdulus carinatus and Triquetrorhabdulus milowii), and Sphenolithus moriformis. Placoliths are mostly dissolved. Assemblages with similar preservation features are present also in Core 199-1220A-4H. In Sample 199-1220A-4H-CC, abundant Ciclycargolithus abisectus was recorded. The first downhole occurrence of a moderately preserved nannofossil assemblage is observed in Core 199-1220A-5H, which contains Oligocene nannofossils. The base of Sphenolithus ciperoensis was recorded in Sample 199-1220A-5H-1, 60 cm, defining the boundary between Subzone CP19a and Zone CP18 (NP24/NP23). The interval corresponding to Zone CP18 (upper part of NP23) is characterized by a diversified assemblage of small Oligocene sphenoliths including Sphenolithus distentus, Sphenolithus predistentus, Sphenolithus tribulosus, and Sphenolithus celsus. In the lower part of Core 199-1220A-5H, the upper range of Sphenolithus pseudoradians is recorded, and its disappearance was located in Sample 199-1220A-5H-5, 45 cm. The boundary between Zones CP18 and CP17 is placed between Samples 199-1220A-6H-3, 100 cm, and 6H-4, 80 cm (in Hole 1220B between Samples 199-1220B-3H-1, 60 cm, and 3H-1, 90 cm) and corresponds to the appearance of S. distentus, which occurs just above an interval with abundant S. moriformis. In the interval from Core 199-1220A-7H to the upper part of Core 8H (Core 4H in Hole 1220B), nannofossil assemblages show variable states of preservation from moderate to poor, representing Subzones CP16c (NP22) and CP16a+b (NP21).

A barren interval begins within Subzone CP16a+b (NP21) in the lowermost Oligocene between Samples 199-1220A-8H-2, 126 cm, and 8H-2, 135 cm. The next downhole occurrence of nannofossils is observed in Sample 199-1220B-18X-1, 20 cm, containing a lower Eocene CP9b/NP11 assemblage, including abundant Tribrachiatus orthostylus, common Discoaster diastypus, and few to rare Discoaster falcatus and Discoaster multiradiatus.

The base of Subzone CP9a (NP10) falls in the gap between Cores 199-1220B-19X and 20X (Fig. F6). Sample 199-1220B-20X-1, 5 cm, represents chalk scraped from a piece of chert, containing a poorly preserved lowermost Eocene assemblage belonging to Subzone CP8b (upper NP9), although similar in composition to the next lower sample (Sample 199-1220B-20X-1, 20 cm) taken from the chalk sequence lying immediately below the chert layer. The uppermost chalk in Core 199-1220B-20X contains Chiasmolithus bidens, Chiasmolithus consuetus, D. multiradiatus, Ellipsolithus distichus, Toweius ?crassus, Toweius eminens, Toweius pertusus, and Rhomboaster spp.

The genus Fasciculithus shows a distinct extinction occurring over a 25-cm interval between Samples 199-220B-20X-1, 90 cm, and 20X-1, 115 cm. The genus Rhomboaster, which is normally poorly preserved because of calcite recrystallization, shows a similarly distinct first occurrence over a 26-cm interval between Samples 199-1220B-20X-1, 125 cm, and 20X-2, 1 cm. The crossover in abundance between these two genera appears to be an event that is easier to recognize than the first or last occurrence of members of these genera, respectively, and occurs between Samples 199-1220B-20X-1, 105 cm, and 20X-1, 115 cm. The fasciculiths are abundant (10-15 specimens per field of view at 1000x magnification) just below their extinction level and includes species such as Fasciculithus alanii, Fasciculithus bobii, Fasciculithus involutus, Fasciculithus richardii, Fasciculithus schaubii, and Fasciculithus tympaniformis. In contrast to the diversity among the fasciculiths, rhomboasters are characterized by a low diversity in the lower part of their range, probably only consisting of a single species, Rhomboaster cuspis. Subsequently, specimens with extended corners (long armed) appear. The evolution and problematic taxonomic status of the Rhomboaster/Tribrachiatus lineage was discussed at length by Romein (1979) and more recently by Bybell and Self-Trail (1995, 1997) and Aubry (1996).

The Rhomboaster/Fasciculithus first/last occurrence events occur 0.77-1.38 m above the base of a multicolored interval in Section 199-1220B-20X-2 (see "Unit V" in "Lithostratigraphy"). The base of this interval holds the P/E boundary Benthic Extinction Event (BEE). The Rhomboaster/Fasciculithus events are present above the P/E boundary but exactly when they occurred in the earliest Eocene remains uncertain.

Calcareous nannofossils were studied in each color band above the BEE (in interval 199-1220B-20X-2, 0-78.5 cm). Sample levels and total abundance are listed below: all centimeter levels refer to depth in Section 199-1220B-20X-2. For a detailed description of color and lithology, see "Unit V" in "Lithostratigraphy."

1 cm = light yellow-brown calcareous silt: abundant nannofossils, with a marked improvement in preservation compared to the underlying sediments. The taxonomic composition is similar to the 85-cm level, including complete specimens of Thoracosphaera spp. This group of calcareous dinoflagellates flourished for a short time interval in low and middle latitudes immediately following the demise of oceanic micro- and nannoplankton at the Cretaceous/Tertiary boundary (e.g., Romein, 1977; Thierstein and Okada, 1979; Perch-Nielsen, 1981; Monechi, 1985). The abundance of Thoracosphaera spp., in a short interval immediately overlying the P/E boundary sediments from Hole 1220B, probably reflects a change of critical boundary condition(s) in surface waters, allowing this opportunistic group to rapidly expand and thrive for a brief period of time.
46 cm = light yellow-brown calcareous silt: few nannofossils and poor preservation. The taxonomic composition is similar to the 85-cm level.
55 cm = brown clay: barren of calcareous nannofossils.
62 cm = black manganese-rich layer: rare nannofossils and poor preservation. The taxonomic composition is similar to the 85-cm level and includes Heliolithus ?floris.
65 cm = yellowish red (upper "pink" layer): barren of calcareous nannofossils.
66.5 cm = light yellowish brown clay between the upper and lower "pink" layers: barren of calcareous nannofossils.
68 cm = light yellowish red (lower "pink" layer): rare but diverse nannofossil assemblage, the taxonomic composition is similar to the 85-cm level, plus Zygodiscus spp.
75 cm = brownish yellow structureless clay: barren of calcareous nannofossils.
85 cm= very pale brown nannofossil chalk, abundant nannofossils showing poor preservation: C. bidens, Coccolithus pelagicus, Discoaster mohleri, D. multiradiatus, Discoaster nobilis, F. involutus, F. richardii, F. schaubii, F. tympaniformis, Prinsius bisulcus, Sphenolithus primus, Thoracosphaera spp., T. eminens, T. pertusus, and abundant fragments of shield rims including those from Campylosphaera and Ericsonia. Sample 199-1220B-20X-CC holds a virtually identical assemblage. The entire Core 199-1220B-20X belongs to Zone CP8 (NP9).

Planktonic Foraminifers

The Eocene-Oligocene radiolarian-rich sediments, which comprise much of the sequence recovered at Site 1220, are largely barren of planktonic foraminifers. However, diverse and moderately well-preserved assemblages of planktonic foraminifers are present in the condensed (~10 m) P/E boundary carbonate sequence overlying basement in Hole 1220B. These assemblages include the distinctive P/E "excursion taxa," which can be used to approximate the P/E boundary (Kelly et al., 1996, 1998). The presence of upper Paleocene-lower Eocene species is recorded in Table T3.

The red clay and radiolarian ooze of Cores 199-1220A-1H through 4H (Units I and II) is barren of planktonic foraminifers, apart from the occasional appearance of thick-walled dissolution-resistant forms. Cores 199-1220A-5H and 6H, which also have a nannofossil ooze component, contain rare and poorly preserved specimens of Subbotina euapertura and Subbotina utilisindex, in addition to Paragloborotalia opima opima and Paragloborotalia opima nana. P. opima opima is present in Samples 199-1220A-5H-3, 60-65 cm, to 6H-4, 40-44 cm, and indicates the presence of Oligocene strata between 30.6 and 27.1 Ma (upper Zone P19 to P21). Cores 199-1220A-7H through 12H are barren of planktonic foraminifers. Core 199-1220B-9H is approximately depth-correlative with Core 199-1220A-12H. The interval between Cores 199-1220B-9H through 17X is composed mainly of radiolarian ooze and is barren of planktonic foraminifers. Visual observations of Cores 199-1220B-9H to 17H indicated an absence of carbonate sediment; therefore, we confined our sampling to core catchers in this interval.

The carbonate content increases dramatically in lithostratigraphic Unit III, and planktonic foraminifers are present from Core 199-1220B-18X to the base of the hole. Preservation is poor near the top of the chalk but improves downhole. Core 18X contains rare and poorly preserved specimens of Acarinina coalingensis and Acarinina soldadoensis, which broadly indicate a late Paleocene-early Eocene age. Sample 199-1220B-19X-1, 77-79 cm, contains Morozovella marginodentata, Morozovella aequa, Acarinina quetra, Subbotina triangularis, and Globanomalina psueodoimitata as well as A. coalingensis and A. soldadoensis. Sample 199-1220B-19X-CC shows slightly better preservation and, in addition to the species listed above, contains Morozovella subbotinae, Subbotina patagonica, Acarinina berggreni, and Igorina lodoensis. We assign these samples to Zone P6 based on the absence of the Zone P5 marker, Morozovella velascoensis, and the Zone P7 marker, Morozovella aragonensis.

The last occurrence of Morozovella acuta occurs between Samples 199-1220B-20X-1, 59-66 cm, and 20X-2, 0-4 cm (198.90-198.45 mbsf; 216.70-217.61 mcd), and is used to approximate the P5/P6 zonal boundary. The numerical age estimate for this datum is listed as 54.7 Ma by Berggren et al. (1995). However, Berggren et al. (1995) also say that this event occurs "midway between the -17 (54.4 Ma) and +19 (54.0 Ma) ash beds in Hole 550" (see table 8 in Berggren et al., 1995), which implies that the disappearance of M. acuta occurs at 54.2 Ma.

A set of small-volume (~0.5-1.0 cm3) samples was examined from the P/E boundary interval in order to document the presence of planktonic foraminifers without resorting to destructive sampling. These samples were derived from surface scrapings through Sections 199-1220B-20X-1 and 20X-2, and each spans an interval of 7.5 cm. Samples from Section 199-1220B-20X-1 contain mainly undifferentiated and poorly preserved planktonic foraminiferal assemblages, including the species M. subbotinae, A. coalingensis, A. soldadoensis, Acarinina nitida, S. patagonica, and occasional Morozovella apanthesma. We assign these samples to Zones P5 and P6.

The P/E boundary is approximated in Core 199-1220B-20X by the presence of excursion taxa, which are present above and below the interval of dramatic color change (interval 199-1220B-20X-2, 48-78 cm). The excursion species include rare to abundant Acarinina africana, few to trace numbers of Acarinina sibaiyaensis, and occasional specimens of Morozovella allisonensis. Specimens of A. africana frequently display very lobate peripheries and approach a clavate chamber shape. Extreme morphotypes of A. sibaiyaensis with more than six chambers in the last whorl are rare, but examples with five or six loosely coiled chambers that display the low rate of chamber enlargement typical of this species are relatively common. Likewise, extreme forms of M. allisonensis with biconvex shells are very rare, but specimens with strongly recurved sutures and weakly developed keels similar to specimens figured by Kelly et al. (1996, 1998) are typical of examples found at Site 1220. In addition to the excursion taxa, we found a number of unusual morozovellids with only three chambers in the last whorl and the tendency to develop nontrochospiral shells. These specimens may represent aberrant forms of M. acuta or Morozovella parva. Also present in samples from adjacent to the P/E boundary are the species Globanomalina planoconica and Globanomalina ovalis, along with an unidentified compressed variety of Chiloguembelina and a very low trochosprial form that we refer to as Pseudohastigerina sp.

Benthic foraminifers suggest that the P/E boundary should be placed at the base of the series of multicolored yellow, pink, black, and brown beds, near 78 cm in Section 199-1220B-20X-2. The presence of excursion fauna such as M. allisonensis, A. africana, and A. sibaiyaensis below this level in Section 199-1220B-20X-2 suggests that these species evolved prior to the P/E boundary and only became abundant at other localities in the Pacific (Ocean Drilling Program [ODP] Site 865; Kelly et al., 1996), Atlantic (ODP Site 1051; Norris and Röhl, 1999), and Tethys (Egypt and Spain) (Kelly et al., 1998) during the episode of global warming associated with the P/E boundary. Unfortunately, the oldest Hole 1220B sediments that immediately overlie basalt contain all three species in the excursion fauna; therefore, we are unable to determine the evolutionary first appearance of these species using this site.

A persistent but rare member of P/E boundary planktonic foraminifer assemblages is a clavate species that we identify as Parasubbotina paleocenica. These specimens are mostly small (<250 µm) and have three to five fingerlike chambers that are flattened slightly when seen in edge view. The aperture is a subsymmetrical equatorial high-arched slit bordered by a distinctive lip. Whole specimens are present between Samples 199-1220B-20X-CC and 20X-2, 13-20 cm. Prior to Leg 199, P. paleocenica, originally described as Clavatorella paleocenica (see Coxall et al., in press, for discussion), has been reported only from its Paleocene type locality in Senegal, West Africa (e.g. De Klasz and De Klasz, 1986, 1988).

Benthic Foraminifers

Benthic foraminiferal assemblages fall into two categories at this site, with clearly differentiated stratigraphic ranges. Calcareous assemblages occurred in lower Miocene, Oligocene, and lower Eocene-uppermost Paleocene sediment. The benthic foraminiferal assemblages from the Miocene and Eocene intervals consist of agglutinated foraminifers (Samples 199-1220A-2H-CC and 8H-CC and 199-1220B-4H-CC and 9H-CC through 13H-CC). Calcareous foraminifers are moderately well preserved in Samples 199-1220A-3H-CC and 4H-CC. The preservation of Oligocene calcareous foraminifers is good. However, upper Eocene and lower Paleocene foraminifers are poorly preserved, and many specimens show signs of calcite overgrowth on the test surface. Agglutinated assemblages are also poorly preserved and show low species diversity. All tube-shaped forms, such as Rhizammina and Martinottiella, are fragmented. Samples 199-1220A-1H-CC, 9H-CC, and 10H-CC and 199-1220B-5H-CC, 6H-CC, 8H-CC, 16X-CC, and 17X-CC are barren. The distribution of benthic foraminifers is reported in Table T4.

Lower Miocene and Oligocene foraminiferal assemblages are characterized by diversified species of the genera Globocassidulina, Cibicidoides, Gyroidinoides, and stilostomellids. Large tests of foraminiferal species such as Cibicidoides mundulus, Cibicidoides grimsdalei, Cibicidoides praemundulus, Cibicidoides havanensis, Oridorsalis umbonatus, and Siphonodosaria abyssorum are consistently present in Sections 199-1220A-3H-CC through 7H-CC. Calcareous assemblages in Sections 3H-CC through 7H-CC co-occur with deep-sea agglutinated species such as Rhizammina sp., Thalmannammina sp., Martinottiella communis, Ammovertellina sp., Cribrostomoides spp., Recurvoides sp., and Ammodiscus sp. These agglutinated taxa, together with the calcareous taxa such as C. mundulus, C. havanensis, and C. grimsdalei, suggest lower bathyal and lower abyssal paleodepths.

Middle-upper Eocene benthic foraminiferal assemblages are poorly preserved and include only the elongate tests of Rhizammina sp. These depauperate agglutinated assemblages appear to indicate lower bathyal paleodepths.

Lower Eocene foraminiferal assemblages are recognized in Samples 199-1220B-18X-CC; 19X-1, 77-79 cm; 19X-CC; and 20X-2, 1.5-3.5 cm. The most common benthic foraminifers are Abyssamina quadrata, A. poagi, Anomalinoides praeacuta, Aragonina aragonensis, Nonion havanensis, O. umbonatus, and Nuttallides truempyi. Of these species, the three species, A. quadrata, A. poagi, and N. truempyi, are extremely abundant and their total relative abundances account for 41% of Sample 199-1220B-18X-CC; 51% of Sample 199-1220B-19X-1, 77-79 cm; 33% of Sample 199-1220B-19X-CC; and 48% of Sample 199-1220B-20X-2, 1.5-3.5 cm. Other lower Eocene species are characterized by specimens that are unusually small for these taxa.

Sample 199-1220B-20X-CC contains some of the Velasco-type benthic assemblages, such as Gavelinella beccariiformis, Lenticulina whitei, Neoflabellina semireticulata, Aragonina velascoensis, Pullenia coryelli, Gyroidinoides globosus, Gyroidinoides quadratus, and Neoeponides hillebrandti. However, preservation of these species is poor, and the tests are overgrown with calcite crystals.

P/E Boundary

Using glass microscope slides, 12 samples were scraped from the surface of Section 199-1220B-20X-2 and analyzed to constrain the P/E boundary. Benthic foraminifers showed dramatic changes throughout these samples. Benthic foraminifers are extremely rare in Samples 199-1220B-20X-2, 13-20 cm; 20X-2, 28-35 cm; and 20X-2, 35-43 cm, where taxa such as N. truempyi, O. umbonatus, and Praebulimina sp. are characterized by their small size. The foraminifers are also very thin walled. In contrast, planktonic foraminifers are very abundant and constitute a planktonic foraminiferal ooze (Fig. F7). Based on qualitative estimations, the ratio of planktonic to benthic foraminifers in these samples is ~100 to 1. Both benthic and planktonic foraminifers decrease in abundance downcore, and fragmented planktonic foraminiferal tests increase adjacent to the multicolored beds near the P/E boundary. N. truempyi, O. umbonatus, and Praebulimina sp. are very poorly preserved and show secondary calcite overgrowths on test surfaces in Sample 199-1220B-20X-2, 42-50 cm. Both benthic and planktonic foraminifers are absent from Samples 199-1220B-20X-2, 50-57 cm; 20X-2, 57-64.5 cm; and 20X-2, 65-72 cm. These intervals show the most marked color changes in this core and are associated with well-developed dolomite crystals. Sample 199-1220B-20X-2, 74-78 cm, includes poorly preserved N. truempyi, O. umbonatus, Bulimina tuxpamensis, Gaudryina pyramidata, and Praebulimina sp., all of which are heavily recrystallized. Planktonic foraminifers are rare in this sample. Members of the Velasco-type assemblage such as G. beccariiformis, Neoflabellina semicribrata, and L. whitei are found in Samples 199-1220B-20X-2, 77.5-85 cm, and 20X-2, 88-95 cm. These samples contain abundant small (~160-190 µm) crystals of dolomite (Fig. F7), whose growth may account for the poor preservation of these species. Planktonic foraminifers are very rare in these samples. The stratigraphic distribution of benthic foraminifers in Section 199-1220B-20X-2 is shown in Figure F8.

Based on the last occurrence of the taxa of the Velasco-type assemblage in Sample 199-1220B-20X-2, 77.5-85 cm, the P/E boundary is identified at a depth of 199.68 mbsf in this hole.

Radiolarians

Abundant and well-preserved radiolarians are present in all recovered material except for the first two cores of Hole 1220A, which contained only trace amounts of poorly preserved nonage diagnostic forms. Radiolarian datum levels are reported in Table T5.

Samples 199-1220A-3H-2, 45-47 cm, and 3H-4, 45-47 cm, contain common but moderately well preserved species indicative of the lowermost Miocene Zone RN1. The boundary between Zones RN1 and RP22, as defined by the first appearance of Cyrtocapsella tetrapera, lies between Samples 199-1220A-3H-4, 45-47 cm, and 3H-5, 45-47 cm. As was the case at Sites 1218 and 1219, this is underlain by a relatively short upper Oligocene sequence (Zone RP22), an expanded upper Oligocene sequence (Zone RP21), and the single lower Oligocene Zone RP20. The boundary between Zones RP22 and RP21 lies between Samples 199-1220A-4H-2, 45-47 cm, and 4H-3, 45-47 cm. The boundary between Zones RP21 and RP20 lies between Samples 199-1220A-5H-CC and 6H-1, 45-47 cm. This boundary was also documented in Hole 1220B between Samples 199-1220B-2H-4, 38-40 cm, and 2H-CC.

Material examined from Samples 199-1220A-4H-6, 45-47 cm, and 4H-CC (lower Zone RP21 and upper Zone RP20) shows considerable reworking of middle Eocene forms (e.g., Dictyoprora mongolfieri, Calocyclas hispida, Podocyrtis [Lampterium] chalara, Podocyrtis [Lampterium] goetheana, and Thyrsocyrtis triacantha) as does Samples 5H-CC and 6H-6, 45-47 cm. The lower part of Zone RP20 and uppermost Zone RP19 contain few to abundant diatoms in the >63-µm fraction of Samples 199-1220A-7H-2, 45-47 cm, to 8H-4, 46-48 cm. The competitive influence of an expanded diatom flora, and probably cooler water temperatures, in this part of the stratigraphic column may account for the generally less diverse radiolarian fauna and hence a less detailed lower Oligocene biozonation. Similar influxes of diatoms were also noted at Sites 1218 and 1219 at about the same stratigraphic horizon. Zones RP21 and RP20 also include a rich orosphaerid population.

Zone RP19 crosses the E/O boundary with the division between Zones RP20 and RP19 lying between Samples 199-1220A-8H-2, 20-22 cm, and 8H-3, 46-48 cm, and Samples 199-1220B-3H-CC and 4H-CC. The boundary between the upper Eocene Zones RP19 and RP18 lies between Samples 199-1220A-8H-6, 46-48 cm, and 8H-7, 46-48 cm, and between Samples 199-1220B-4H-CC and 5H-CC. Zone RP17 was not sampled in Hole 1220B, but it must lie within Core 199-1220B-5H; in Hole 1220A, the boundary between Zones RP18 and RP17 lies between Samples 199-1220A-9H-6, 45-47 cm, and 9H-7, 45-47 cm.

The underlying middle Eocene sequence is uniformly rich in radiolarians, and all the middle Eocene radiolarian zones except RP10 can be recognized. The boundary between Zones RP17 and RP16, marked by the first occurrence of Cryptocarpium azyx, lies between Samples 199-1220A-10H-4, 45-47 cm, and 10H-5, 45-47 cm. Although P. (L.) goetheana, which marks the lower limit of Zone RP16, is scarce, the boundary between Zones RP16 and RP15 can be placed between Samples 199-1220A-11H-7, 45-47 cm, and 11H-CC and Samples 199-1220B-7H-CC and 8-CC. Zone RP14 is the lowermost Hole 1220A radiolarian zone, and its boundary with the overlying Zone RP15 is between Samples 199-1220A-12H-4, 45-47 cm, and 12H-5, 45-47 cm. In Hole 1220B, the boundary between Zones RP15 and RP14 lies between Samples 199-1220B-9H-1, 45-47 cm, and 9H-2, 45-47 cm. In Hole 1220B the boundary between Zones RP15 and RP14 lies between Samples 199-1220B-9H-1, 45-47 cm, and 9H-2, 45-47 cm.

Abundant and well-preserved radiolarians persist downhole in Hole 1220B to Zone RP11. The boundary between Zones RP14 and RP13 lies between Samples 199-1220B-10H-3, 45-47 cm, and 10H-4, 45-47 cm. The boundary between Zones RP13 and RP12 lies between Samples 199-1220B-11H-1, 45-47 cm, and 11H-2, 45-47 cm, and the boundary between Zones RP12 and RP11 lies between Samples 199-112B-12H-CC and 13H-1, 45-47 cm. The material recovered in Core 199-1220B-13H below Section 13H-3 showed characteristics of flow-in. Cores 199-1220B, 14X and 15X consist of chert fragments. Abundant and well-preserved radiolarians could again be recognized in Sample 199-1220B-16X-1, 100-102 cm, and can be placed in Zone RP8. This zone continues down to its boundary with Zone RP7 between Samples 199-1220B-17X-CC and 18X-2, 10-12 cm. No zonal assignment was possible for Sample 199-1220B-18X-CC or for subsequent cores, which are barren of radiolarians.

A similar sequence was found in the lower part of Hole 1220C. Sample 199-1220C-11H-3, 10-12 cm, belongs to either Zone RP11 or RP12, whereas Sample 199-1220C-11H-4, 10-12 cm, can definitely be placed in Zone RP11. Once more, only chert was recovered in Cores 199-1220C-12X and 13X. However, abundant and well-preserved radiolarians could again be identified in Samples 199-1220C-14X-3, 60-62 cm, and 14X-6, 60-62 cm, as belonging to Zone RP8. No radiolarians were found in subsequent cores.

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