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Pospichal, James J (1991): Abundance of calcareous nannofossils in ODP Hole 121-752B (Table 1). PANGAEA,, Supplement to: Pospichal, JJ (1991): Calcareous nannofossils across Cretaceous/Tertiary boundary at Site 752, eastern Indian Ocean. In: Weissel, J; Peirce, J; Taylor, E; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 121, 395-413,

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A biostratigraphically complete Cretaceous/Tertiary boundary was recovered during Ocean Drilling Program Leg 121. The boundary, cored in ODP Hole 752B on Broken Ridge, is the most expanded deep-sea section yet recovered by ODP/DSDP. The initial Danian subzone, CP la, spans nearly 5 m and the underlying uppermost Maestrichtian Nephrolithus frequens Zone extends 50 m below the boundary. The paleolatitude of Broken Ridge at Cretaceous/Tertiary time is estimated at 50°-55°S which includes this site among the latest in a series of complete or near complete high southern latitude Cretaceous/Tertiary boundary sections recovered by ODP (Leg 113 Site 690 and Leg 119 Site 738).
The boundary at Site 752 lies at the base of a thick (6-6.5 m) volcanic ash unit composed of multiple ash layers which overlies indurated Maestrichtian chalks. Magnetostratigraphy indicates that the boundary lies within Subchron 29R, which is the case for all other known complete sections for which the polarity has been determined. Anomalous abundances of the trace element iridium are present at the boundary. A second iridium peak, 80 cm above the boundary, corresponds to an increase in redeposited Cretaceous nannofossils.
The nannofossil succession is similar to that found at previously studied austral high-latitude ODP drill sites with few differences due to the more northerly location of this site. Individual nannofossil species were counted and placed into three categories. A plot of the percent abundance of Cretaceous, Tertiary, and 'survivor' groups illustrates the rapid replacement of the Cretaceous nannoflora by 'survivor' forms beginning at the boundary and the dominance of this latter group through the initial Danian biozone. This 'survivor' or opportunistic assemblage is then rapidly replaced by newly evolved Tertiary taxa. The assemblage of the uppermost Maestrichtian is biased toward dissolution-resistant forms such as Micula decussata. In those few intervals where preservation is good, the dissolution susceptible species, Prediscosphaera stoveri, is more prevalent and overall diversity of the assemblage is higher. The 'survivor' assemblage is dominated by Zygodiscus sigmoides and Thoracosphaera. The Tertiary assemblage consists of rare Biantholithus sparsus, the first of this group to appear. It is followed several meters upsection by Cruciplacolithus primus. Cruciplacolithus tenuis and small Prinsius spp. dominate the assemblage beginning at about 5 m above the boundary.
Latitude: -30.891000 * Longitude: 93.577500
Date/Time Start: 1988-05-18T09:00:00 * Date/Time End: 1988-05-22T12:30:00
Minimum DEPTH, sediment/rock: 349.02 m * Maximum DEPTH, sediment/rock: 373.05 m
121-752B * Latitude: -30.891000 * Longitude: 93.577500 * Date/Time Start: 1988-05-18T09:00:00 * Date/Time End: 1988-05-22T12:30:00 * Elevation: -1097.0 m * Penetration: 435.6 m * Recovery: 112.34 m * Location: South Indian Ridge, South Indian Ocean * Campaign: Leg121 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 17 cores; 158 m cored; 0 m drilled; 71.1 % recovery
<1 = present but not within 500 count
#NameShort NameUnitPrincipal InvestigatorMethodComment
1EpochEpochPospichal, James J
2Nannofossil zoneNannos zonePospichal, James J
3Sample code/labelSample labelPospichal, James JODP sample designation
4DEPTH, sediment/rockDepthmGeocode
5Nannofossils preservationNannos preservPospichal, James JSmear slide analysisG = good, M = moderate, P = poor
6Nannofossils indeterminataNannos indetPospichal, James JSmear slide analysisV = very abundant (>10 specimens per field of view at 1560 X), A = abundant (6-10 specimens per field), C = common (1-5 specimen per field), F = few (one specimen per 2-10 fields), R = rare (one specimen per >10 fields of view)
7Nannofossils, tertiaryNannos tertiary#Pospichal, James JSmear slide analysis
8Nannofossils, cretaceousNannos cretaceous#Pospichal, James JSmear slide analysis
9Nannofossils, survivorNannos survivor#Pospichal, James JSmear slide analysis
10NannofossilsNannos#Pospichal, James JSmear slide analysistotal
11Acuturris scotusA. scotus#Pospichal, James JSmear slide analysis
12Ahmuellerella octoradiataA. octoradiata#Pospichal, James JSmear slide analysis
13Arkhangelskiella cymbiformisA. cymbiformis#Pospichal, James JSmear slide analysis
14Bidiscus rotatoriusB. rotatorius#Pospichal, James JSmear slide analysis
15Biscutum constansB. constans#Pospichal, James JSmear slide analysis
16Chiastozygus amphiponsC. amphipons#Pospichal, James JSmear slide analysis
17Chiastozygus sp.Chiastozygus sp.#Pospichal, James JSmear slide analysis
18Corollithion rhombicumC. rhombicum#Pospichal, James JSmear slide analysis
19Cretarhabdus conicusC. conicus#Pospichal, James JSmear slide analysis
20Cribrosphaerella daniaeC. daniae#Pospichal, James JSmear slide analysis
21Cribrosphaerella ehrenbergiiC. ehrenbergii#Pospichal, James JSmear slide analysis
22Eiffellithus turriseiffeliiE. turriseiffelii#Pospichal, James JSmear slide analysis
23Eiffellithus sp.Eiffellithus sp.#Pospichal, James JSmear slide analysis
24Gartnerago spp.Gartnerago spp.#Pospichal, James JSmear slide analysis
25Kamptnerius magnificusK. magnificus#Pospichal, James JSmear slide analysis
26Lithraphidites quadratusL. quadratus#Pospichal, James JSmear slide analysis
27Micula decussataM. decussata#Pospichal, James JSmear slide analysis
28Nephrolithus frequens frequensN. frequens frequens#Pospichal, James JSmear slide analysis
29Nephrolithus frequens miniporusN. frequens miniporus#Pospichal, James JSmear slide analysis
30Prediscosphaera cretaceaP. cretacea#Pospichal, James JSmear slide analysis
31Prediscosphaera spinosaP. spinosa#Pospichal, James JSmear slide analysis
32Prediscosphaera stoveriP. stoveri#Pospichal, James JSmear slide analysis
33Watznaueria barnesaeW. barnesae#Pospichal, James JSmear slide analysis
34Zygodiscus spiralisZ. spiralis#Pospichal, James JSmear slide analysis
35Biscutum notaculumB. notaculum#Pospichal, James JSmear slide analysisreworked
36Nephrolithus corystusN. corystus#Pospichal, James JSmear slide analysisreworked
37Phanulithus obscurusP. obscurus#Pospichal, James JSmear slide analysisreworked
38Reinhardtites levisR. levis#Pospichal, James JSmear slide analysisreworked
39Tranolithus phacelosusT. phacelosus#Pospichal, James JSmear slide analysisreworked
40Zygodiscus compactusZ. compactus#Pospichal, James JSmear slide analysisreworked
41Zygodiscus diplogrammusZ. diplogrammus#Pospichal, James JSmear slide analysisreworked
42Biscutum castrorumB. castrorum#Pospichal, James JSmear slide analysis
43Braarudosphaera bigelowiiB. bigelowii#Pospichal, James JSmear slide analysis
44Cyclagelosphaera reinhardtiiC. reinhardtii#Pospichal, James JSmear slide analysisC. reinhardtii/ C. alta
45Lapidaecassis sp.Lapidaecassis sp.#Pospichal, James JSmear slide analysis
46Markalius apertusM. apertus#Pospichal, James JSmear slide analysis
47Markalius inversusM. inversus#Pospichal, James JSmear slide analysis
48Neocrepidolithus cruciatusN. cruciatus#Pospichal, James JSmear slide analysis
49Neocrepidolithus fossusN. fossus#Pospichal, James JSmear slide analysis
50Neocrepidolithus neocrassusN. neocrassus#Pospichal, James JSmear slide analysis
51Thoracosphaera spp.Thoracosphaera spp.#Pospichal, James JSmear slide analysis
52Zygodiscus sigmoidesZ. sigmoides#Pospichal, James JSmear slide analysis
53Zygolithus cruxZ. crux#Pospichal, James JSmear slide analysis
54Zygolithus sp.Zygolithus sp.#Pospichal, James JSmear slide analysisrotated cross
55Biantholithus sparsusB. sparsus#Pospichal, James JSmear slide analysis
56Coccolithus cavusC. cavus#Pospichal, James JSmear slide analysisC. cavus / C. pelagicus
57Cruciplacolithus primusC. primus#Pospichal, James JSmear slide analysis<5 µm
58Cruciplacolithus primusC. primus#Pospichal, James JSmear slide analysis>5 µm
59Cruciplacolithus tenuisC. tenuis#Pospichal, James JSmear slide analysis>7 µm
60Prinsius tenuiculumP. tenuiculum#Pospichal, James JSmear slide analysisP. tenuiculum / P. dimorphosus
61Futyania petalosaF. petalosa#Pospichal, James JSmear slide analysis
62Placoliths, smallPlacoliths small#Pospichal, James JSmear slide analysisMiscellaneous small oval placoliths
4087 data points

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