Abundance of calcareous nannofossils in ODP Hole 121-752B (Table 1)
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| Format: | Dataset Open Access |
| Langue: | en |
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PANGAEA
1991
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| _version_ | 1867169021440294912 |
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| author | Pospichal, James J |
| author_facet | Pospichal, James J |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | 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. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_729024 |
| institution | PANGAEA |
| language | en |
| publishDate | 1991 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Abundance of calcareous nannofossils in ODP Hole 121-752B (Table 1) Pospichal, James J 121-752B; Acuturris scotus; Ahmuellerella octoradiata; Arkhangelskiella cymbiformis; Biantholithus sparsus; Bidiscus rotatorius; Biscutum castrorum; Biscutum constans; Biscutum notaculum; Braarudosphaera bigelowii; Chiastozygus amphipons; Chiastozygus sp.; Coccolithus cavus; Corollithion rhombicum; Cretarhabdus conicus; Cribrosphaerella daniae; Cribrosphaerella ehrenbergii; Cruciplacolithus primus; Cruciplacolithus tenuis; Cyclagelosphaera reinhardtii; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Eiffellithus sp.; Eiffellithus turriseiffelii; Epoch; Futyania petalosa; Gartnerago spp.; Joides Resolution; Kamptnerius magnificus; Lapidaecassis sp.; Leg121; Lithraphidites quadratus; Markalius apertus; Markalius inversus; Micula decussata; Nannofossils; Nannofossils, cretaceous; Nannofossils, survivor; Nannofossils, tertiary; Nannofossils indeterminata; Nannofossils preservation; Nannofossil zone; Neocrepidolithus cruciatus; Neocrepidolithus fossus; Neocrepidolithus neocrassus; Nephrolithus corystus; Nephrolithus frequens frequens; Nephrolithus frequens miniporus; Ocean Drilling Program; ODP; Phanulithus obscurus; Placoliths, small; Prediscosphaera cretacea; Prediscosphaera spinosa; Prediscosphaera stoveri; Prinsius tenuiculum; Reinhardtites levis; Sample code/label; Smear slide analysis; South Indian Ridge, South Indian Ocean; Thoracosphaera spp.; Tranolithus phacelosus; Watznaueria barnesae; Zygodiscus compactus; Zygodiscus diplogrammus; Zygodiscus sigmoides; Zygodiscus spiralis; Zygolithus crux; Zygolithus sp. 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. |
| title | Abundance of calcareous nannofossils in ODP Hole 121-752B (Table 1) |
| topic | 121-752B; Acuturris scotus; Ahmuellerella octoradiata; Arkhangelskiella cymbiformis; Biantholithus sparsus; Bidiscus rotatorius; Biscutum castrorum; Biscutum constans; Biscutum notaculum; Braarudosphaera bigelowii; Chiastozygus amphipons; Chiastozygus sp.; Coccolithus cavus; Corollithion rhombicum; Cretarhabdus conicus; Cribrosphaerella daniae; Cribrosphaerella ehrenbergii; Cruciplacolithus primus; Cruciplacolithus tenuis; Cyclagelosphaera reinhardtii; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Eiffellithus sp.; Eiffellithus turriseiffelii; Epoch; Futyania petalosa; Gartnerago spp.; Joides Resolution; Kamptnerius magnificus; Lapidaecassis sp.; Leg121; Lithraphidites quadratus; Markalius apertus; Markalius inversus; Micula decussata; Nannofossils; Nannofossils, cretaceous; Nannofossils, survivor; Nannofossils, tertiary; Nannofossils indeterminata; Nannofossils preservation; Nannofossil zone; Neocrepidolithus cruciatus; Neocrepidolithus fossus; Neocrepidolithus neocrassus; Nephrolithus corystus; Nephrolithus frequens frequens; Nephrolithus frequens miniporus; Ocean Drilling Program; ODP; Phanulithus obscurus; Placoliths, small; Prediscosphaera cretacea; Prediscosphaera spinosa; Prediscosphaera stoveri; Prinsius tenuiculum; Reinhardtites levis; Sample code/label; Smear slide analysis; South Indian Ridge, South Indian Ocean; Thoracosphaera spp.; Tranolithus phacelosus; Watznaueria barnesae; Zygodiscus compactus; Zygodiscus diplogrammus; Zygodiscus sigmoides; Zygodiscus spiralis; Zygolithus crux; Zygolithus sp. |
| url | https://doi.org/10.1594/PANGAEA.729024 |