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Studies on the crustal structure of the Turkana Rift Zone (TRZ) in northern Kenya and southern Ethiopia began in the early 1980s. Initially driven by hydrocarbon exploration, these studies revealed that the rift zone comprises multiple fault-bounded basins ranging in age from the Eocene to the present. They also showed that the area hosts the intersection zone of the N-S trending basins of the Cenozoic East African Rift System (EARS) and the NW-SE-trending Mesozoic-Paleogene Central African Rift System (CARS). However, early seismic reflection and borehole data were mostly concentrated in the southern TRZ, resulting in limited subsurface data for its northern counterpart. This data gap has led to an incomplete understanding of the rift zone's regional crustal structure and how earlier CARS-related rifting influenced the development of the present-day EARS. Here, we leverage newly collected onshore and offshore subsurface industry datasets in the TRZ, spanning a 300 x 150 km region, to characterize the TRZ's crustal structure. We map several key subsurface horizons using a dense grid of 363 2-D seismic reflection profiles, which we tie to surface geology and borehole datasets. Mapping the acoustic basement produced new structure contour maps that provide high-resolution constraints on the TRZ’s crustal structure. Additionally, our isopach maps of key horizons show that strain migrated toward the modern rift axis, located along the center of Lake Turkana, following the widespread eruption of the Gombe Group basalt around 4 million years ago. Together, these results indicate that the area of maximum subsidence is collocated with the area transected by the CARS. Thus, we propose that these earlier episodes of rifting may have influenced the development and evolution of the modern EARS in the northern TRZ. These results provide crucial information for understanding tectonics in the context of hominin evolution and offer new insights into forming a divergent plate boundary. 

Reconstructions of eastern African vegetation and climate are critical for understanding primate and large mammal evolution in the Neogene. Insight into past ecological conditions can be gleaned from lipid biomarkers preserved in sedimentary archives, providing evidence for the role of habitats (e.g. open vs. closed vegetation) on evolutionary trait selection. A common paleoecological proxy is the 𝛿¹³C of n-alkanes, which integrates the distinct isotopic signatures of C3 and C4 vegetation. In typical modern tropical ecosystems, “woody” vegetation uses C3 photosynthesis while “grassy” vegetation uses C4 photosynthesis. Under these conditions, mixing models can then estimate the fraction of woody cover of a landscape. While the use of photosynthetic pathways to infer plant functional type (PFT) is powerful, this paradigm does not hold prior to the rise of C4 grasses at 10 Ma, leaving a gap in understanding of ecosystem structure in the early-mid Miocene. To address this issue, we investigate whether n-alkane chain length distributions (rather than 𝛿¹³C) hold information about plant functional type independent of photosynthetic pathway. Here, we present n-alkane chain length data from over 800 modern plant samples, representing a variety of different photosynthetic pathways, growth forms, habitats, and locations. This dataset comprises a significant literature review component, as well as over 400 new distributions generated in this study. We build upon our previous work using PCA and turn to non-linear methods – including both supervised neural network classifiers and unsupervised dimensionality reduction – to determine the potential of n-alkane distributions for PFT identification. Successful differentiation between woody and grassy PFTs using modern plant n-alkane chain lengths will provide a foundation for applying this tool to the geologic record. Our method will compliment well-established isotopic measurement practices while offering the novel ability to reconstruct vegetation structure in pure C3 ecosystems. This represents a particularly powerful tool for understanding ecological history prior to the rise of C4 grasses.