60th Annual Report on Research 2015

Statement of the problem

The timing of sediment erosion from source regions has a direct implication in the petroleum field in deciphering the timing of major reservoir rock formation in the depositional sink areas. However, the timing of major erosional pulse/s is often associated with uncertainties and controversies. The Blue Nile River network on the Ethiopian Plateau in East African Rift System has incised a 1.6 km deep canyon and supplying ~96% of the Nile sediment load. This sediment load is being deposited to the alluvial fans of Sudan, the Nile Delta and the Nile deep-sea Fan in the Mediterranean. This study is motivated by the necessity of constraining incision history of the Blue Nile that has gained considerable momentum over the past years, where some argues for old and others suggesting a young incision of the plateau. The objective of the proposed study is to initiate this robust research using state-of-the art techniques of integrating apatite (U-Th)/He and ⁴He/³He thermochronometry. This study will provide crucial data for understanding and constraining incision history of the Ethiopian Plateau as the timing of erosion is critical in understanding temporal probability of reservoir vs. organic-rich source rocks development in the Nile petroleum plays, particularly in the Mediterranean Sea. Moreover, this study holds enormous potential for constraining tectonic models of the northeastern East African Rift, including the formative mechanisms and dynamics of rift faults likely linked to paleotopographic evolution of the Ethiopian Plateau.

Research Effort

This ACS-PRF funding allowed the PI to successfully initiate a large-scale research at the early stage of her academic career in a tenure-track faculty position at a reputed primarily undergraduate institution. The PI is developing a collaborative effort with Dr. Mathijs van Soest at Arizona State University as part of this study. Three geology undergraduate students Helen Flynn, Cody Meservy and Christopher William are actively pursuing their undergraduate research experience directly linked to this project. Another geology student Brittiny Moore has completed some of the preliminary works related to this project as part of her undergraduate research work. Graduate student Nathaniel Blackburn is also working in his MS thesis directly linked to the project supported by Western Kentucky University (WKU) internal seed grants. During summer of 2014, and spring and fall of 2015, the PI and the graduate and undergraduate students accomplished the following project-related tasks:

1) Significant literature survey on the research problem, 2) geological and 3D DEM map generation in ArcGIS showing major structural, tectonic, and morpho-tectonic features of the study area and sample locations, 3) initial labwork for understanding and implimenting the technical aspects of rock sample preparation, thin sections, heavy liquid separation and mineral picking. 4) Nine rock samples have been prepared, heavy and light minerals were isolated, 5) 55 euhedral apatite grains were picked, 6) (U-Th)/He dating of these grains are now ongoing at Arizona State University (ASU) Group 18 laboratory as part of the PI’s collaborative effort with ASU.

In last year, the PI and both graduate and undergraduate students presented their initial research findings at multiple annual national and regional conferences including Geological Society of America at Vancouver, Canada, American Association of Petroleum Geologists at Houston, Kentucky Academy of Science and Western Kentucky University annual Student Research Conference. One paper was published in peer-reviewed journal this year and one is in press to be published towards the end of this year.

Initial findings:

The PI collected samples from both basement and sedimentary rocks exposed at the Blue Nile canyon wall in a vertical transect. Following are some of the initial results of the project:

1) 55 apatite grains were extracted from basement and sedimentary rocks. Preliminary data of apatite He dates ranges from 58.9 to 460 Ma. These cooling ages are older than expected as compared to some previous works. Wide ranges of the apatite He dates obtained from this PRF-supported project exhibit significant data dispersion that cannot be explained simply by age and elevation relationship. These data dispersion can therefore be explained by radiation damage, grain size and effective uranium concentration eU. 2) These cooling ages positively correlate with effective uranium (eU) concentration. Thus the Radiation Damage Accumulation and Annealing thermal model was demonstrated to be appropriate for regions such as the Ethiopian Plateau with a complex thermal history.

Securing additional funds:

Securing additional funds was only possible because of this PRF support for the initial work of this project. Nathaniel Blackburn has obtained additional funding from 3 different sources to help support and disseminate his research results and continue his MS thesis. In summer 2014, he was awarded $3500 summer stipend from WKU internal grant RCAP to carry out lab works related to sample preparation, mineral separation and picking. He was also awarded $550 travel scholarship from Geological Society of America (GSA) On To The Future program to present his research at the GSA annual meeting in Vancouver, Canada. He also received several funding including graduate and travel stipends and scholarships from Western Kentucky University Geography and Geology Department, Graduate School and Veteran Affair to support and continue his MS research. Undergraduate students Helen Flynn and Brittiny Moore secured WKU Faculty-Undergraduate Student Engagement internal grant of $6500 for additional support to continue their undergraduate research, which was made possible because of the PI’s ACS-PRF grant that initiated their undergraduate research.