Mebrahtu Fisseha Weldeghebriel

Mebrahtu Fisseha Weldeghebriel
Princeton University | PU · Department of Geosciences

PhD

About

18
Publications
3,530
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61
Citations
Introduction
I am broadly interested in ancient-ocean chemistry, paleoclimatology, and low-temperature geochemistry of chemical sediments, particularly evaporites. My research focuses on (1) documenting the chemical composition of ancient seawater using direct measurements of “fluid inclusions” in marine halite, (2) understanding what controls the long-term chemical evolution of Earth's oceans, (3) linking changes in the chemistry of ancient seawater to climate, pCO2, and marine biological evolution.
Additional affiliations
August 2016 - present
Binghamton University
Position
  • Graduate teaching assistant
Description
  • Teaching labs and teaching-related duties to assist professors with grading.
September 2011 - June 2015
Eritrea Institute of Technology
Position
  • Graduate Assistant
Description
  • *Performing teaching for undergraduate courses such as General Geology, Introduction to Rock-Forming Minerals, Introduction to Geophysics, and Geological Map Interpretation. *Teaching-related duties to assist faculty members and tutoring classes. *Supervising and coordinating geological field trips and lab works. * Advise undergraduate students, grade exams, and prepare grade summary sheets.
Education
September 2006 - June 2011
Eritrea Institute of Technology
Field of study
  • Geology

Publications

Publications (18)
Article
The Berrechid sub-basin of Morocco consists of Late Triassic–Early Jurassic evaporites and red beds that are part of the syn-rift Atlantic series. Although some of the Berrechid sub-basin has been extensively studied, the depositional environment of the Upper Salt-Mudstone Formation has long been debated, with some early studies proposing a marine...
Article
Reconstructing the lithium isotope composition (δ7Li) of ancient seawater and lacustrine environment is crucial for tracing silicate weathering processes that regulate Earth's carbon cycle and climate. This study examines the reliability of evaporite minerals in preserving the Li isotope signature of the original brines from which they precipitate....
Article
Full-text available
The surficial cycling of Mg is coupled with the global carbon cycle, a predominant control of Earth’s climate. However, how Earth’s surficial Mg cycle evolved with time has been elusive. Magnesium isotope signatures of seawater (δ ²⁶ Mg sw ) track the surficial Mg cycle, which could provide crucial information on the carbon cycle in Earth’s history...
Article
Full-text available
Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales are well documented, but the causes of these changes are debated. Fluid inclusions in marine halite indicate that the Li concentration in seawater [Li+]SW declined sevenfold over the past 150 million years (Ma) from ~184 μmol/kg H2O a...
Article
Chemical analyses of 1371 fluid inclusions in 131 halite samples with marine 87Sr/86Sr values were used to reconstruct the strontium concentrations [Sr]SW of Phanerozoic and Neoproterozoic seawater. [Sr]SW varied seven-fold and oscillated twice between high- and low-Sr concentrations over the past 550 million years (Myr), in rhythm with Ca-rich and...
Preprint
Full-text available
The surficial cycling of Mg is directly coupled with the global carbon cycle, a predominant control of Earth’s climate. However, how Earth’s surficial Mg cycle evolved with time had been elusive. Magnesium isotope signatures of seawater (δ ²⁶ Mg sw ) track the surficial Mg cycle, which could provide crucial information on the carbon cycle in Earth’...
Article
Chemical analyses of 2,618 (1,640 new and 978 published) fluid inclusions in marine halite were used to define paleoseawater [Ca²⁺] and [SO2−4] over the past 550 million years (Myr). Three types of fluid inclusion brine chemistries were recognized based on measured [Ca²⁺] and [SO2−4]: (1) SO4-rich with [SO2−4] ≫ [Ca²⁺]; (2) Ca-rich with [Ca²⁺] ≫ [S...
Article
Previous studies have confirmed that primary fluid inclusions in halite record and preserve information concerning the major ion chemistry of seawater. Here, we determine ratios of redox sensitive trace metals (Fe, Mn, V, Mo, U) in paleo-seawater trapped as primary fluid inclusions in halite from two boreholes (Przyborów IG3, Gorzów Wielkopolski IG...
Article
Sedimentological studies of modern halites have focused on shallow water to subaerially- exposed saline pans, where in-place crystal growth, dissolution, and cementation textures dominate. Clastic halite transported and deposited by waves and unidirectional currents as bedload is poorly known. This paper (1) describes and interprets the diagnostic...
Article
Full-text available
Quantitative multi-element analyses of single fluid inclusions in halite and other sedimentary minerals can provide information on the origin and chemical evolution of ancient surface waters on Earth. Integrated laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and cryogenic-scanning electron microscopy-energy dispersive spect...
Conference Paper
The concentrations of the major ions [Mg2+], [Ca2+], and [SO42-] in seawater have varied systematically in the Phanerozoic. Such changes influenced the mineralogy of marine skeletal organisms and inorganic carbonates because the Mg/Ca ratio of seawater controls which carbonate, calcite or aragonite, is favored to precipitate (Stanley et al. 2005)....
Conference Paper
The major-ion chemistry of seawater (Na+, Mg2+, Ca2+, K+, Cl-, SO42-, HCO3-) has varied in the Phanerozoic. Such changes are reflected in the mineralogy of marine nonskeletal limestones, evaporites, and shell-building organisms. Preliminary Laser ablation ICP-MS results show that conservative minor and trace element concentrations in primary fluid...

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