Deborah Tangunan

University College London | UCL · Department of Earth Sciences

The isolation of specific grain size classes of lithogenic samples and biogenic carbonate from the <63 µm fraction (i.e. clay and silt) of marine sediment is often a prerequisite to further pre-treatments and/or analytical measurements for palaeoceanographic studies. Established techniques employed have included sieving, settling and micro-filtrati...

The late Miocene‐early Pliocene (7.4‐4.5 Ma) is a key interval in Earth's history where intense reorganization of atmospheric and ocean circulation occurred within a global cooling scenario. The Southern African monsoon (SAFM) potentially played an important role in climate systems variability during this interval. However, the dynamics of this imp...

The Pliocene Epoch (∼5.3–2.6 million years ago, Ma) was characterized by a warmer than present climate with smaller Northern Hemisphere ice sheets, and offers an example of a climate system in long‐term equilibrium with current or predicted near‐future atmospheric CO2 concentrations (pCO2). A long‐term trend of ice‐sheet expansion led to more prono...

Prior to ~1 million years ago (Ma), variations in global ice volume were dominated by changes in obliquity; however, the role of precession remains unresolved. Using a record of North Atlantic ice rafting spanning the past 1.7 million years, we find that the onset of ice rafting within a given glacial cycle (reflecting ice sheet expansion) consiste...

In the southern Indian Ocean, the position of the subtropical front-the boundary between colder, fresher waters to the south and warmer, saltier waters to the north-has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the s...

We present a 500-kyr productivity reconstruction of the southwest Indian Ocean (MD96–2077; Natal Valley) and the eastern South Atlantic (Sites 1266; Walvis Ridge) from coccolithophore assemblages and coccolith geochemistry. The study sites are situated in two different hydrographic regimes: one located in the upper boundary of the Agulhas Current (...

In late 2016, the IODP Expedition 366 drilled 21 holes on summits and flanks of three serpentinite mud volcanoes (SMVs) of the Mariana Forearc: Yinazao (Blue Moon), Fantangisña (Celestial), and Asùt Tesoru (Big Blue). The drilling reached the forearc sediments underneath the SMVs only at Site U1498 where, according to data from this study, the bios...

“Once Upon a Time… a Scientific Fairy Tale” is an award-winning project that aims to communicate science and promote the dialogue between scientists and the public. At the heart of this project, there is a set of short stories (tales) with scientific content in a clear language, illustrated by professional and amateur artists. The stories cover dif...

A detailed paleoenvironment reconstruction from the Mozambique Channel, western Indian Ocean, based on the calcareous nannoplankton assemblages was conducted for the interval between 2.85 and 1.85 Myr. This study covers the period during which the successive extinction of the last five species of discoasters occurred. New productivity data obtained...

We present a new calcareous nannofossil paleoproductivity reconstruction of the southeastern margin of the Sulu Sea to understand how marine productivity varied through time in one of the major fishing grounds of the Philippine archipelago. The study is based on two sediment cores obtained from two different hydrographic locations in the western eq...

Allen Phonolite is the proposed name for a newly discovered alkaline igneous rock complex in Allen, Northern Samar composed of phonolites and phonolite porphyries. Phenocrysts are made up of large crystals of analcime and diopside. The fine-grained groundmass is composed of K-feldspar, analcime, diopside, magnetite with magnetite and apatite as acc...

We present a new coccolithophore productivity reconstruction spanning the last 300 ka in core GeoB12613-1 retrieved from the western tropical Indian Ocean (IO), an area that mainly derives its warm and oligotrophic surface waters from the eastern IO. Application of a calibrated assemblage-based productivity index indicates a reduction in estimated...

This study investigates the calcareous nannofossil assemblage and composition of 62 field samples collected from a calcareous sedimentary sequence exposed in Mamburao, Occidental Mindoro, Philippines. The sequence consisting of foraminifera-rich, alternating beds of mudstones and fine- to medium-grained sandstones was subjected to stratigraphic log...

The Catbalogan Formation is a sequence of alternating beds of mudstones, sandstones and pebble conglomerates extensively distributed along the road from Rosario to Mondragon, and Catarman to Calbayog in Northern Samar. Most of the mudstones contain calcareous nannofossils while sandstones have benthic foraminifera, coal stringers and fragments of m...

The occurrence of Cretaceous calcareous nannofossils is reported from the limestone units of Codon Formation in Codon Point, San Andres, Catanduanes. The nannofossil assemblage consists of long ranging taxa like Watznaueria spp. (W. barnesiae, W. fossacincta and W. manivitiae) and Late Cretaceous forms including Micula prinsii, Micula praemurus, Mi...

The paper presents the results of a calcareous nannofossil biostratigraphic study of 3 cores obtained from Indahag Limestone within the Laguindingan-Gitagum area in western Misamis Oriental, northern Mindanao. Based on the calcareous nannofossil assemblages and the occurrence of index markers like Discoaster pentaradiatus, Discoaster quadramus, Dis...

Biri Island off Northern Samar is known for its impressive rock formations made up of sedimentary rocks, as well as volcanic flow deposits and agglomerates. Analysis of 55 mudstone to fine-grained sandstone samples collected from five localities around the island revealed poorly-to moderately-preserved calcareous nannofossils. Despite the lack of d...