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Tectonic processes in Papua New Guinea and past productivity in the eastern equatorial Pacific Ocean

Article Abstract:

An investigation of the iron (Fe) perturbations needed to stimulate diatom production requires an assessment of the lowest Fe concentration whereby uptake still allows maximum cellular growth rates and of what Fe flux to surface waters is then required to sustain high diatom productivity once the concentration threshold is exceeded. Research in this area has concluded that climate forcing has definitely had an impact on productivity in the eastern equatorial Pacific. Furthermore, equatorial sediment records give an insight into these impacts. However, some element of this cycling may have been fuelled by localized tectonic processes in the Papua New Guinea island-arc area.

Growth, Isotopes, Iron, Iron (Metal), Diatoms

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Lower Cretaceous deposits trapped near the equatorial Mid-Atlantic Ridge

Article Abstract:

A 140 million year old Maiolica-type pelagic deposit has been recovered from the center of the basin adjacent to the intersection of the Mid-Atlantic Ridge and the Romanche transform fault in a tectonically deformed and uplifted Romanche Sedimentary Sequence (RSS). St. Peter Paul Island may have another such deposit. The RSS is more than 4 km thick and more than 200 km long, including continent-derived quartzitic siltstones of Palaeocene and Eocene age. The deposit raises questions about the equatorial Atlantic's evolution, requiring at least added complexities to the simple, rifting and drifting plate-tectonic scheme.

Paleogeography, Sediments (Geology), Mid-Atlantic Ridge

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Vast Neogene laminated diatom mat deposits from the eastern equatorial Pacific Ocean

Article Abstract:

Several sediment cores in the eastern equatorial Pacific Ocean point to the occurence of repeated episodes of increased equatorial primary production between 15 and 4.4 million years ago. Thalassiothrix diatom mat deposits appeared as successive laminations covering distances of more than 2,000 km. Their deposition may have overwhelmed the benthos so that their laminations were preserved by physical means.

Geology, Stratigraphic, Stratigraphy, Neogene period, Diatomaceous earth

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