Open Access Te Herenga Waka-Victoria University of Wellington
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Paleoenvironmental analysis of early Eocene marl and limestone alternations from Mead Stream, New Zealand

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posted on 2021-12-07, 15:03 authored by Peñafiel Bermudez, Sonja

This study integrates paleonotology and geochemistry to provide a paleoclimatic analysis of cyclic sedimentation in the Lower Marl at Mead Stream in Marlborough, Aotearoa/New Zealand. The alternating marl and limestone bedding in this outcrop coincide with the warmest period in the Paleogene, the Early Eocene Climatic Optimum (EECO).  An acetic acid leaching method was refined and used successfully to extract microfossils from the indurated limestones and marls from two intervals of the Lower Marl. The technique resulted in foraminiferal tests with improved surface ornament in comparison with samples that were processed using standard washing methodology.  The resulting paleontological assessment of leached foraminiferal and radiolarian assemblages coupled with XRF and stable isotope analysis revised the position and detailed the faunal response to the J hyperthermal at the initiation of the EECO. Microfossil assemblages and carbon isotopic data suggest that the J carbon isotopic excursion (CIE) may be a two-stage event. A new L-3 CIE and possible hyperthermal event was identified within the body of the EECO. Both the J and L-3 events contained acmes where Morozovella made up a quarter of the planktic foraminiferal specimens, suggesting the southern expansion of subtropical waters. Fluctuations of Acarinina and Subbotina foraminifera coinciding with the marl and limestone alternations may indicate climate cycles within these hyperthermals.


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Date of Award



Te Herenga Waka—Victoria University of Wellington

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Degree Grantor

Te Herenga Waka—Victoria University of Wellington

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Degree Name

Master of Science

ANZSRC Type Of Activity code

970104 Expanding Knowledge in the Earth Sciences

Victoria University of Wellington Item Type

Awarded Research Masters Thesis



Victoria University of Wellington School

School of Geography, Environment and Earth Sciences


Hannah, Michael; Hollis, Chris