Vegetation dynamics, climate and sea-level changes at the New Jersey Atlantic margin during the Eocene, Oligocene, and Miocene; Abbreviation: DYNJOM
Zusammenfassung der Projektergebnisse
In the framework of project, Oligocene and Miocene ecosytem- and climate development at the coast of New Jersey, USA, could be reconstructed for certain intervals reflected in sediments two sites (M0027 and M0029) from the New Jersey Shallow Shelf, which have been drilled in the framework of IODP Expedition 313 in 2008. The palynofacies within each sequence reflects sea-level change through variation in terrigenous vs. authigenic flux. Very high ratios of terrigenous vs. marine palynomorphs are probably associated with seismic sequence boundaries. Comparison of palynomorphs-based ‘distance from shoreline’ estimates with paleodepth estimates derived from foraminiferal data allows relative sea level to be reconstructed at Sites M0027 and M0029. Milankovitch-scale periodicity is suggested for parasequences visible in thick sequences deposited in relatively deep water where substantial accommodation existed, such as during Miocene climatic optimum at Site M0029. The palynomorphs-based results from Site M0027 imply that conifer forests were restricted to mountainous areas during the very late Eocene/very early Oligocene. Mean annual temperatures were relatively high compared to the following part of the early Oligocene, implying a cooling of ~3 °C. From the ea rly Oligocene to the middle Miocene, the hinterland vegetation of the New Jersey shelf was characterized by oak-hickory forests in the lowlands and conifer-dominated vegetation in the highlands. Cooling events during the Oligocene were paired with expansions of conifer forest. Temperature data reconstructed via C the next-living-relative method imply an increase in annual temperatures from ~12 °C to more than 15 °C during the Oligocene. The Mi-1 cooling event at the onset of the Miocene (~23 million years before present) is reflected by an expansion of conifers and an annual temperature decrease from ~15 °C to ~12.5 °C. A second cooling event known from the Miocene, the Mi-1aa event, was also marked by a decrease in annual temperature. Generally, the Miocene ecosystem and climate conditions were very similar to those of the Oligocene in the hinterland of the New Jersey shelf. There is no evidence for the development of grasslands on the Atlantic coastal plain during the Oligocene and Miocene. One of the most surprising findings is that the ecosystem and climate data for the hinterland of the New Jersey shelf do not show extraordinary changes during the Miocene climatic optimum at ~15 million years before present, except for a minor increase in deciduous-evergreen mixed forest taxa and a decrease in swamp forest taxa. Furthermore, the carbon-isotope record (based on phytoclasts) from Site M0029 from the New Jersey shallow shelf lacks a positive excursion (as revealed in records from other regions) during this interval. An explanation could be that vegetation and regional climate in the hinterland of the New Jersey shelf did not react as sensitively to Oligocene and Miocene climate changes as other regions in North America or Europe, as implied by climate models. An additional explanation for the relatively low regional temperatures reconstructed for the Mid-Miocene climatic optimum, compared to other climate records, could be an uplift of the Appalachian Mountains during the Miocene. A Pleistocene pollen assemblage analyzed in the framework of the project derives from the Marine Isotope Chron 7 or 5e and shows vegetation and climate conditions similar to the present-day conditions in the region.
Projektbezogene Publikationen (Auswahl)
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(2010): Foraminifer- and palynology-based reconstructions of site-shoreline distance, sea-level and ecosystems: new data from the New Jersey Shallow Shelf (IODP Exp. 313). International symposium on foraminifera (“FORAMS”) 2010, Bonn
Kotthoff, U., Katz, M.E., Williams, R., McCarthy, F.M.G., and the IODP Exp. 313 Scientific Party
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(2011): Palynological results from the New Jersey shallow shelf: vegetation development on the Atlantic Coastal Plain and implications for sea-level reconstruction. European Geoscience Union annual meeting 2011, Vienna
Kotthoff, U., McCarthy, F.M.G., Katz, M.E., and the IODP Exp. 313 Scientific Party
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(2012): Environmental and climate change at the Miocene coast of New Jersey: palynology- and sedimentology-based reconstructions. Annual meeting of the Geologische Vereinigung 2012, Hamburg
Kotthoff, U., McCarthy, F.M.G., Fang, L., Hesselbo, S.P., and the IODP Expedition 313 Scientific Party
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(2013): Carbon-isotope stratigraphy from terrestrial organic matter through the Monterey Event, Miocene, New Jersey margin (IODP Expedition 313). Geosphere, 9, 1303-1318
Fang, L., Bjerrum, C., Hesselbo, S.P., Kotthoff, U., McCarthy, M.F.G., Huang, B., Ditchfield, P.W.
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(2013): Eustatic control of New Jersey margin architecture: palynological evidence from IODP Expedition 313, Geosphere, 9
McCarthy, F.M.G., Katz, M., Kotthoff, U., Browning, J., Miller, K., Zanatta, R., Williams, R., Drljepan, M., Hesselbo, S.P., Bjerrum, C., Mountain, G.
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(2013): Oligocene and Miocene vegetation and climate development on the Atlantic Coastal Plain (IODP Expedition 313). European Geoscience Union annual meeting 2013, Vienna
Kotthoff, U., Greenwood, D.R., McCarthy, F.M.G., Müller-Navarra, K., Hesselbo, S.P.
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(2013): Vegetation and climate development on the North American Atlantic Coastal Plain from 33 to 13 million years ago (IODP Expedition 313). Climate of the Past Discussions, 9, 6551-6603
Kotthoff, U., Greenwood, D.R., McCarthy, F.M.G., Müller-Navarra, K., Hesselbo, S.P.
