Calcareous plankton stratigraphy around the Pliocene “Eltanin” asteroid impact area (SE Pacific): documentation and application for geological and paleoceanographic reconstruction
Section snippets
Introduction and objectives
Microfossil analysis of marine sediments related to extraterrestrial impacts is a common tool for biostratigraphic and paleoenvironmental reconstruction. Undoubtedly, the Cretaceous/Tertiary boundary impact is the most significant event in which planktic microfossil biostratigraphy and paleoecology have been used for general reconstruction (e.g., Sidgurdsson et al., 1997). The Eocene is another interval where impact-related structures or material (e.g., microtektites) have been studied, dated
Study area and sediment cores
The studied region is located on the Pacific-Aluk portion of the Antarctic plate, in the Bellingshausen Sea (Fig. 1). In the abyssal portions of this area high-resolution seismic survey with Parasound echosounding has revealed an acoustically well-stratified sequence, underlain by a seismically transparent sediments with a thickness between 20 and 60 m, named the “Eltanin-Polarstern Transparent Zone” (EPTZ) and interpreted as being impact-related (Gersonde et al., 1997). In the area of highest
Autochthonous undisturbed basal sediments—sedimentary unit V
This sedimentary unit (SU V) is well documented in core PS2708-1 (1275–1450 cm) (Fig. 2). The abundance of calcareous nannofossils in this interval is very high, with a moderate degree of preservation. A 20-cm interval analysis of this interval revealed a uniform nannofossil assemblage (Table 2). The presence of common Reticulofenestra umbilicus, whose first occurrence (FO) is situated in the standard Martini (1971) Zone NP 16, as well as the absence of other frequent species in the overlying
Mixture evaluation and sedimentary reconstruction
Displaced sediments ranging in age from Eocene to Pliocene characterized the impact-related sediment interval, consisting of sedimentary units IV to II. The age and lithologies of clasts deposited in SU IV are similar to those of the sediments identified in SU V (Middle Eocene in PS2708-1) plus others including typical Oligocene and Neogene calcareous planktic microfossils. Samples from SU III in core PS2704-1 contain abundant, well-preserved Paleogene and Pliocene foraminifers (Fig. 3),
Acknowledgements
The authors thank S. W. Wise, P. R. Bown, K. von Salis and U. Zielinski for their critical and valuable comments. We also acknowledge the revision of the English version of the manuscript accomplished by N.S.D. Skinner and editorial help by A. Deutsch. Research grants CICYT ANT97-1909-E, CLI-1002-CO2-02 and the Spanish-German Integrated Actions supported this study.
References (38)
- et al.
Southern Ocean Pleistocene calcareous nannofossil eventscalibration with isotope and geomagnetic stratigraphies
Marine Microapleontology
(2000) Biochronology and paleoclimatic implications of middle Eocene to Oligocene planktic foraminiferal faunas
Marine Micropaleontology
(1983)Stepwise mass extinctions and impact eventslate eocene to early oligocene
Marine Micropaleontology
(1986)- et al.
Unmelted meteoritic debris in the Late Pliocene Ir anomalyevidence for the impact of a nonchondritic asteroid
Geochimica et Cosmochimica Acta
(1985) - et al.
A planktic foraminiferal transfer function for the southern South Atlantic Ocean
Marine Micropaleontology
(1998) How many impact-generated microspherule layers in the Upper Eocene?
Palaeogeography, Palaeoclimatology, Palaeoecology
(1995)- et al.
The late early Eocene Montagnais bolideno impact on biotic diversity
Micropaleontology
(1990) - et al.
Pliocene Discoaster abundance variations. Deep Sea Drilling Project Site 606biochronology and paleoenvironmental implications
Initial Reports of DSDP
(1987) Neogene planktic foraminifer magnetostratigraphy of the southern Kerguelen Plateau (Sites 747, 748 and 751)
Proceedings of ODP Scientific Results
(1992)- Berggren, W.A., Kent, D.V., Swisher, C.C., Aubry, M.P., 1995. A revised Cenozoic geochronology and chronostratigraphy....
Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic
Geophysical Research
Upper Pliocene Discoaster abundance from the Atlantic, Pacific, and Indian oceansthe significance of productivity pressure at low latitudes
Memoirs Science Geology
Evolution of the calcareous nannofossil assemblage as a response to the paleoceanographic changes in the Eastern Equatorial Pacific Ocean from 4 to 2 Ma (Leg 138, Sites 849 and 852)
Proceedings of ODP, Scientific Results
Preliminary results from Hole 704AArctic-Antarctic correlation through nannofossil biochronology
Proceedings of ODP, Scientific Results
Neogene calcareous nannofossil biostratigraphy, Leg 116 (Central Indian Ocean)
Proceedings of ODP, Scientific Results
Geological record and reconstruction of the late Pliocene impact of the Eltanin asteroid in the Southern Ocean
Nature
Leg 177 summarysouthern ocean paleoceanography
Proceedings of ODP, Initial Reports
Pliocene closing of the Isthmus of Panama, based on biostratigraphic evidence from nearby Pacific and Caribbean Sea cores
Geology
Cited by (5)
Coccolith dissolution versus productivity changes during the Plio-Pleistocene (3.14–1.80 MA) in the South Atlantic (ODP site 1090)
2022, Palaeogeography, Palaeoclimatology, PalaeoecologyCitation Excerpt :The impact may have caused megatsunamis along the Pacific and the Southern ocean shores and could have affected the climate by ejecting large amounts of salt water into the atmosphere (Gersonde et al., 1997). A sediment core study of the Bellinghausen Sea obtained during the ANT-XII/4 expedition of the R.V. ‘Polarstern’, did not reveal major changes in the calcareous plankton association for the interval immediately after the impact (Flores et al., 2002). However, it documented a reduction in the sedimentation rates and the appearance of extensive bioturbation after the impact that could be a reflection of paleoenvironmental changes immediately after the impact.
Asteroid impact tsunamis
2005, Comptes Rendus PhysiqueOceanic impacts - A growing field of fundamental geoscience
2002, Deep-Sea Research Part II: Topical Studies in OceanographyCatastrophes versus events in the geologic past: How does the scale matter?
2013, Cadernos do Laboratorio Xeoloxico de Laxe