Daniel Gebregiorgis

Daniel Gebregiorgis
Georgia State University | GSU · Department of Geosciences

PhD

About

26
Publications
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246
Citations
Introduction
Skills and Expertise

Publications

Publications (26)
Article
Full-text available
The tropical Pacific influences climate patterns across the globe, yet robust constraints on decadal to centennial‐scale climate variations are difficult to extract from sparse instrumental observations in this region. Oxygen isotope (δ¹⁸O) records from long‐lived corals enable the quantitative reconstruction of tropical Pacific climate variability...
Article
Lake Magadi is an internally drained, saline and alkaline terminal sump in the southern Kenya Rift. Geochemistry of samples from an ~200 m core representing the past ~1 m.y. of the lake’s history shows some of the highest concentrations of transition metals and metalloids ever reported from lacustrine sediment, including redox-sensitive elements mo...
Article
Full-text available
The late Miocene was a period of declining CO2 levels and extensive environmental changes, which likely had a large impact on monsoon strength as well as on the weathering and erosion intensity in the South Asian Monsoon domain. To improve our understanding of these feedback systems, detrital clays from the southern Bay of Bengal (International Oce...
Article
Full-text available
We present new mineralogical and geochemical data from modern sediments in the Chew Bahir basin and catchment, Ethiopia. Our goal is to better understand the role of modern sedimentary processes in chemical proxy formation in the Chew Bahir paleolake, a newly investigated paleoclimatic archive, to provide environmental context for human evolution a...
Article
Full-text available
Tectonics and regional monsoon strength control weathering and erosion regimes of the watersheds feeding into the Bay of Bengal, which are important contributors to global climate evolution via carbon cycle feedbacks. The detailed mechanisms controlling the input of terrigenous clay to the Bay of Bengal on tectonic to orbital timescales are, howeve...
Article
Full-text available
Fungi are highly sensitive to environmental and climatic changes. Palaeoecological reconstructions utilising tropical African fungal spores, however, are rare and patchy. Here, we show that fossil fungal spores preserved in core KAP‐01 from the Cherangani Hills in Kenya tracks critical environmental changes in the African tropics since the Last Gla...
Article
Full-text available
Plain Language Summary Lake sediments contain a rich archive of information about past climate change. Clay minerals in such sediments, in particular, can potentially provide important insight into changes in humidity and aridity in the terrestrial environment by recording changes in precipitation as reflected in lake salinity. Until now, the clima...
Article
We report on indium nitride growth on sapphire substrates by migration-enhanced plasma-assisted metal organic chemical vapor deposition (MEPA-MOCVD). The growth is studied in the temperature range from 700 °C to 957 °C, well above the decomposition temperature of indium nitride in conventional MOCVD. Raman spectroscopy, atomic force microscopy, and...
Article
Full-text available
We report on the influence of various plasma species on the growth and structural properties of indium nitride in plasma-assisted metalorganic chemical vapor deposition. Atomic emission spectroscopy was used to quantify the molecular, neutral, and ionized nitrogen species concentrations above the growth surface. Reflectance and Raman spectroscopy a...
Article
There is paucity in the proxy records available for the reconstruction of vegetation and climate histories of tropical eastern Africa, especially north of the equator. Here, we present a new paleoenvironmental record based on a 3.5-m sediment core from the Kapkanyar mire, Cherangani Hills, Kenya. Using analyses of pollen, microscopic charcoal, and...
Article
Full-text available
The dominant large-scale interannual modes in the tropical Pacific and Indian Oceans—El Niño southern oscillation (ENSO) and the Indian Ocean Dipole (IOD)—dominate seasonal rainfall patterns in Ethiopia. However, there is a clear interaction between ENSO and the IOD, and it is unclear whether the IOD has an independent influence on seasonal monsoon...
Conference Paper
The Olduvai Gorge of northern Tanzania contains an important record of early hominin fossils and artifacts dating from the Plio-Pleistocene. Situated on the western edge of the East African Rift, the Olduvai Gorge is carved into the Serengeti Plain of East Africa where late Cenozoic environmental fluctuations in East Africa are thought to influence...
Article
Full-text available
The orbital-scale timing of South Asian monsoon (SAM) precipitation is poorly understood. Here we present new SST and seawater δ¹⁸O (δ¹⁸Osw) records from the Bay of Bengal, the core convective region of the South Asian monsoon, over the past 1 million years. Our records reveal that SAM precipitation peaked in the precession band ~9 kyrs after North...
Article
The past variability of the South Asian Monsoon is mostly known from records of wind strength over the Arabian Sea while high-resolution paleorecords from regions of strong monsoon precipitation are still lacking. Here, we present records of past monsoon variability obtained from sediment core SK 168/GC-1, which was collected at the Alcock Seamount...
Data
The past variability of the South Asian Monsoon is mostly known from records of wind strength over the Arabian Sea while high-resolution paleorecords from regions of strong monsoon precipitation are still lacking. Here, we present records of past monsoon variability obtained from sediment core SK 168/GC-1, which was collected at the Alcock Seamount...
Article
The Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with glacial-interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments draining into the Andaman Sea remains poorly constrained. Here, we use radiogenic Sr, Nd, and Pb isotope compositions of the detrital clay-size fra...

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Projects

Projects (3)
Project
To come up with a comprehensive climate and environmental history of East African landscapes and note the major changes that have occurred in the Holocene period. To know the effect of human interaction with their immediate environment and how it has affected the climate over the stated period.
Project
Mainly working on reconstructing the physical properties (e.g. SST, SSS) of the the South Asian monsoon and assessing the link between Earth's orbital cycles (Eccentricity, Obliquity, Precession cycles or the so called Milankovitch cycles) and the monsoon climate.