Paleocene and Eocene Calcareous Nannofossils from Deep Sea Drilling Project Legs 25 and 40, South and East of Africa

Mackenzie, Debora; S.W., Jr.

doi:10.2973/dsdp.proc.71.147.1983

Cited by 12 publications

(3 citation statements)

References 20 publications

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“…Accordingly, Ramsay (1972Ramsay ( , 1977, and Ramsay et al (1973) suggested that the percentage of discoasterids in a given sample is an indicator of the intensity of the dissolution that the sample has undergone. Similarly, MacKenzie and Wise (1983) used the ratio of discoasterids to placoliths as a measure of dissolution.…”

Section: Taxonomic Methodsmentioning

confidence: 99%

“…The problems inherent to dissolution and overgrowth in calcareous nannofossils are numerous and complex (MacKenzie and Wise, 1983), and the potential quality of their preservational state for monitoring the chemical state of bottom water awaits comparison with other dissolution-susceptible parameters. However, in this study, we have paid special attention to preservation features to contribute to a general topic of Leg 115. Three methods are currently used to evaluate the preservation state of calcareous nannofossils: (1) a qualitative preservation scale; (2) the visual preservation scale proposed by Roth and Thierstein (1972), in which the degree of etching and overgrowth is evaluated; and (3) the taxonomic features of the assemblage, like species diversity and ratios among taxa with different preservation potential.…”

Section: Preservationmentioning

confidence: 99%

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Late Oligocene through Early Pleistocene Calcareous Nannofossils from Western Equatorial Indian Ocean (Leg 115)

Rio¹,

Fornaciari²,

Raffi³

1990

Proceedings of the Ocean Drilling Program

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The chronostratigraphy, the calcareous nannofossil biochronology, and the biostratigraphy of the Miocene and Pliocene sediments retrieved during Leg 115 in the equatorial western Indian Ocean are presented and discussed. Most of the zonal boundaries of the standard 1971 zonation of Martini and the 1973 zonation of Bukry are easily recognized in these low-latitude sediments. We also comment on the secondary events that are proposed in the literature to improve the biostratigraphic resolution provided by the standard zonations.The study of calcareous nannofossil biostratigraphy and taphonomy of sequences from the Northern Mascarene Plateau area, which was drilled to investigate the Neogene history of carbonate flux and dissolution, indicate that the accumulation of carbonates in this area results from a complex interplay among carbonate bioproductivity, carbonate removal by chemical dissolution and mechanical erosion, and carbonate addition by mass and current transport. In spite of these drawbacks, major changes and trends in carbonate accumulation can be recognized, most of which, if not all, correlate with major steps in the evolution of the Neogene climatic system.

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Section: Taxonomic Methodsmentioning

confidence: 99%

Section: Preservationmentioning

confidence: 99%

Late Oligocene through Early Pleistocene Calcareous Nannofossils from Western Equatorial Indian Ocean (Leg 115)

Rio¹,

Fornaciari²,

Raffi³

1990

Proceedings of the Ocean Drilling Program

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“…This datum coin cides with the highest occurrence of C. solitus in DSDP Site 386 (Okada and Theirstein, 1979), Hole 548A (Muller, 1985), and Hole 400A (Muller, 1979). In addition, the lowest occurrence of R. bisecta falls within the R. umbilica Zone (NP16-NP17) in DSDP Holes 362A and 363 (Proto- Decima et al, 1978) and in Hole 360 (MacKenzie and Wise, 1983), and it occurs in two samples (about 2 m) below the highest occurrence of C. solitus in Site 538A (Lang and Watkins, 1984). In Islas Orcados (IO) Core 16-43, R. bisecta co-occurs with C. solitus over an interval of 60 cm, but in IO Core 16-44, no R. bisecta was reported in conjunction with C. solitus in the Discoaster bifax Subzone (Wise and Mostajo, 1983).…”

Section: Eocenementioning

confidence: 81%

Eocene and Oligocene Calcareous Nannofossils from the Labrador Sea, ODP Leg 105

Firth¹

1989

Proceedings of the Ocean Drilling Program

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During Ocean Drilling Program (ODP) Leg 105, a thick sequence of lower Eocene to lower Oligocene sediments was recovered from Hole 647A in the southern Labrador Sea. These sediments contain diverse, well-preserved, high-latitude calcareous nannofossil flora. The nannofossil biostratigraphy of the hole indicates the presence of a minor hiatus be tween Zones NP 16 and NP 17 in the upper middle Eocene and a barren interval separating Zones NP 13 and NP 15. Spe cies abundance is highest within the lower to middle Eocene and starts to decline near the base of the upper Eocene. No major change in the nannoflora was observed across the Eocene/Oligocene boundary, although a slight decrease in spe cies abundance was recorded. The Paleogene calcareous nannofossils of nearby DSDP Site 112 were reexamined and compared with those of Site 647. Several cores were reassigned to different nannofossil zones. The calcareous nanno flora are dominated by high-latitude indicative species and also exhibit a high diversity, which suggests the influence of more temperate water masses in this region during Eocene and Oligocene time. One new subspecies from the middle Eo cene, Sphenolithus furcatolithoides labradorensis, is described.

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Environmental perturbations at the early Eocene ETM2, H2, and I1 events as inferred by Tethyan calcareous plankton (Terche section, northeastern Italy)

et al. 2016

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Several early Eocene hyperthermals have been recently investigated and characterized in terms of temperature anomalies and oceanographic changes. The effects of these climatic perturbations on biotic communities are much less constrained. Here we present new records from the Terche section (northeastern Italy) that, for the first time, integrates data on planktic foraminifera and calcareous nannofossils across three post‐Paleocene‐Eocene Thermal Maximum negative carbon isotope excursions (CIEs). The biomagnetostratigraphic framework generated at Terche allows us to confidently relate such CIEs to the Eocene Thermal Maximum 2 (ETM2), H2, and I1 events. Each of these events coincides with lithological anomalies characterized by significantly lower calcium carbonate content (marly units, MUs). We interpret these MUs as mainly linked to an effect of increased terrigenous dilution, as dissolution proxies do not display significant variations. Calcareous plankton assemblages change significantly across these events and radiolarians increase. Observed changes suggest that transient warming and environmental perturbations, though more intense during ETM2, occurred during each of the three investigated perturbations. Variations among calcareous plankton suggest increase in surface‐water eutrophication with respect to the pre‐event conditions, coupled with a weakening of the upper water‐column thermal stratification. Higher nutrient discharge was related to intensification of the hydrological cycle as a consequence of the warmer climate. These conditions persisted during the early CIE recovery, implying slower recovery rates for the environment and biota than for the carbon cycle.

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Paleocene and Eocene Calcareous Nannofossils from Deep Sea Drilling Project Legs 25 and 40, South and East of Africa

Cited by 12 publications

References 20 publications

Late Oligocene through Early Pleistocene Calcareous Nannofossils from Western Equatorial Indian Ocean (Leg 115)

Late Oligocene through Early Pleistocene Calcareous Nannofossils from Western Equatorial Indian Ocean (Leg 115)

Eocene and Oligocene Calcareous Nannofossils from the Labrador Sea, ODP Leg 105

Environmental perturbations at the early Eocene ETM2, H2, and I1 events as inferred by Tethyan calcareous plankton (Terche section, northeastern Italy)

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