March 24 @ 12:00 pm - 12:50 pm CDT
Departmental Research in Earth Science
Who: Chenliang Wu & Chenhao Yang
When: Noon, 3/24/17
Where: Room 100, KWGL
Wu: Backwater control on fluvial-deltaic stratigraphy, tested in the Western Irish Namurian Basin, County Clare, Ireland
The hydrodynamics of rivers approaching a basin are influenced by the onset of non-uniform ‘backwater’ conditions that give rise to decelerating flow velocity and decreasing boundary shear stress. These changes occur across a spatial gradient, in which decreasing sediment transport capacity triggers morphodynamic responses that include sediment deposition at the transition from uniform to non-uniform flow near the outlet. As a consequence, channel width-to-depth ratios and bed sediment grain size decrease downstream. While non-uniform flow and associated morphodynamic responses are well understood in modern fluvial-deltaic systems, the influences on the rock record remains a subject of active debate. This represents a signific ant, unresolved gap between morphodynamic concepts established in geomorphology and fluvial-deltaic stratigraphy. This proposal seeks to identify linkages between strata and morphodynamics by measuring variability in fluvial deposits across the backwater zone identified for the Tullig Cyclothem in the Western Irish Namurian Basin (WINB). The results of this analysis will bolster analytical models that seek to link observed stratigraphy with predicted sediment accumulation patterns. Furthermore, the proposed research provides a basis for a direct assessment of the diachronous nature of the fluvial-deltaic stratigraphy in the WINB by combining time-and-space variable changes in grain size and channel dimension with reconstructions of paleo-hydraulics. This research will produce quantitative metrics to evaluate the dimensions, connectivity, and grain size variation of channel bodies produced by ancient fluvial-deltaic systems, and thereby provide valuable geological insights into hyd rocarbon bearing rocks.
Yang: Seismic imaging of the lithospheric structure and deformation beneath China: what controls intraplate seismicity of the continental China?
Plate tectonic theory describes the Earth as made up of rigid plates whose relative motions are accommodated along narrow plate boundaries. However, it has difficulty in explaining large-scale intraplate deformation that can be spread out over several thousand kilometers instead of being concentrated in a narrow zone around a plate boundary, for example, continental China. As the major part of east Eurasia, the mainland of China is highly diverse in geology, consisting of various Eurasia, the mainland of China is highly diverse in geology, consisting of various modern tectonics of China is the result of a long and complicated evolution of collision, subduction, and amalgamation of microcontinents and fold belts with Precambrian nuclei. Whether and how the structure anomalies are associated with the observed large and heterogeneously distributed surface deformation is still not well understood. In my study, I applied receiver function analysis techniques to the China Earthquake Administration (CEA) array data to image the curst-mantle boundaries and measure the average crustal Vp/Vs ratio beneath Mainland China, and employ a common-reflection-point stacking scheme to estimate the LAB depth beneath China using ScS reverberation phases generated by large deep earthquakes occurring in the western Pacific. The primary goal is to find better relationship between the intraplate seismicity with the lithospheric structure and deformation beneath China.