ICDP workshop on the Lake Victoria Drilling Project (LVDP):Scientific Drilling of the World’s Largest Tropical Lake

Lake Victoria, which is bordered by Uganda, Tanzania, Kenya and has a catchment that extends to Rwanda and Burundi, is home to the largest human population surrounding any lake in the world and provides critical resources across eastern Africa. Lake Victoria is also the world’s largest tropical lake by surface area, but it is relatively shallow and without a major inlet, making it very sensitive to changes in climate, and especially hydroclimate. Furthermore, its size creates abundant habitats for aquatic fauna, including the iconic hyper-diverse cichlids, and serves as a major geographic barrier to terrestrial fauna across equatorial Africa. Given Lake Victoria’s importance to the eastern African region, its sensitivity to climate, and its influences on terrestrial and aquatic faunal evolution and dispersal, it is vital to understand the connection between the lake, regional climate, and how the lake size, shape, and depth has changed through its depositional history. This information can only be ascertained by collecting a complete archive of Lake Victoria’s sedimentary record. To evaluate Lake Victoria basin as a potential drilling target, ~50 scientists from 10 countries met in Dar es Salaam, Tanzania in July 2022 for the International Continental Scientific Drilling Program (ICDP) sponsored Lake Victoria Drilling Project (LVDP) workshop. Discussions of the main scientific objectives for a future drilling project included: 1) recovering the Pleistocene and Holocene sedimentary records of Lake Victoria that document the dynamic nature of the lake, including multiple lacustrine and paleosol sequences; 2) establishing the chronology of recovered sediments, including using extensive tephra fingerprinting and other techniques from deposits in the region; 3) reconstructing past climate, environment, lacustrine conditions, and aquatic fauna, using an integrated multi-proxy approach, combined with climate and hydrologic modeling; and 4) connecting new records with existing sedimentary snapshots and fossils exposed in deposits around the lake, tying archeological, paleontological, sedimentological, tectonic, and volcanic findings to new drilling results. The LVDP provides an innovative way to address critical geological, paleontological, climatological, and evolutionary biological questions about Quaternary to modern landscapes and ecosystems in eastern Africa. Importantly, this project affords an excellent opportunity to help develop conservation and management strategies for regional responses to current and future changes in climate, land use, fisheries, and resiliency of at-risk communities in equatorial Africa

Remnants of an ancient forest provide ecological context for Early Miocene fossil apes

The lineage of apes and humans (Hominoidea) evolved and radiated across Afro-Arabia in the early Neogene during a time of global climatic changes and ongoing tectonic processes that formed the East African Rift. These changes probably created highly variable environments and introduced selective pressures influencing the diversification of early apes. However, interpreting the connection between environmental dynamics and adaptive evolution is hampered by difficulties in locating taxa within specific ecological contexts: time-averaged or reworked deposits may not faithfully represent individual palaeohabitats. Here we present multiproxy evidence from Early Miocene deposits on Rusinga Island, Kenya, which directly ties the early ape Proconsul to a widespread, dense, multistoried, closed-canopy tropical seasonal forest set in a warm and relatively wet, local climate. These results underscore the importance of forested environments in the evolution of early apes

Megafloral change in the early and middle Paleocene in the Williston

This paper presents a quantitative analysis of megafloral changes in composition and diversity using collections of early and middle Paleocene floras (65.51 to~58 Ma) in the Williston Basin of North Dakota, USA. Based on the floral composition and stratigraphic ranges of taxa, the Williston Basin floral record can be subdivided into three megafloral zones (WBI, WBII, and WBIII), each representing ≥ 1 myr. The floral record of the basin implies that local and regional paleoenvironmental and climatic changes contributed to transitions in the early and middle Paleocene plant communities. The Williston Basin floral record documents a decrease in species richness that mirrors a decrease in mean annual temperatures from the latest Cretaceous to middle Paleocene. These results, combined with previous work from the Hanna and Bighorn Basins, suggest that climate may have played an important role in patterns of floral diversity and plant community composition. Further, these data indicate that it took Paleocene plant communities in the Northern Great Plains millions of years to reach diversity levels common in the Cretaceous

Appendix 1 - Morphotype Catalog

Ojo Alamo Sandstone Morphotype Catalog Morphological descriptions, botanical affinities, photographs, and line drawings of all identified Ojo Alamo Sandstone megafloral morphotypes. All dicotyledonous angiosperm leaf morphotypes were described using the Manual of Leaf Architecture (Ellis et al. 2009). Each dicotyledonous angiosperm leaf morphotype description contains leaf architecture description, margin classification, and Raunkiaer-Webb (Webb 1959) size classification. All other groups (i.e. dicotyledonous angiosperm reproductive structures, pteridophytes, monocotyledonous angiosperms, and conifers) were described based on their gross morphology. Botanical affinities of morphotypes were determined after comparison with previously published taxonomy. Each morphotype also has a specimen number which corresponds with the morphotype exemplar. See Supplementary Table 1 for detailed systematic morphotype list and Supplementary Table 2 for morphotype abundance by fossil locality

Supplementary Figure 2 - Digital Leaf Physiognomy Examples

Examples of the 4 different types of leaves prepared for digital leaf physiognomy (DiLP) following the protocol of Peppe et al. 2011. All digital preparation was done using Adobe Photoshop

Supplementary Tables 1-8

Supplementary Tables 1-8 which includes (1) systematic list of megafloral morphotypes from the San Juan Basin, (2) stratigraphic position, depositional facies, location, and morphotype tallies for all floral sites, (3) megafloral census data, (4) megafloral presence-absence data, (5) total Ojo Alamo Sandstone and facies mean physiognomic variables using the DiLP paleoclimate calculation, (6) measured leaf physiognomy values for all measureable specimens/morphotypes, (7) regional diversity comparison, and (8) - calculated p-values for Margalef Index, Pielou's Evenness, and Berger-Parker Index for all San Juan Basin, Denver Basin, and Williston Basin diversity indice comparison

Supplementary Figure 1 - Facies and Formation Photos Small

Generalized latest Cretaceous and earliest Paleocene stratigraphic units and Ojo Alamo Sandstone lithofacies. A: contact between the Maastrichtian Naashoibito Member of the Kirtland/Fruitland Formation and the overlying earliest Paleocene Ojo Alamo Sandstone. B: the contact between the earliest Paleocene Ojo Alamo Sandstone and overlying early Paleocene Nacimiento Formation. C: representative overbank leaf Locality AF1409D in the Ojo Alamo Sandstone. D: closeup of the overbank flora deposits which are interbedded siltstone and medium to coarse grained sandstone and have been interpreted to represent downstream accretionary bars. E: is a coarse grained cross-bedded sandstone with occasional gravel lag deposits which account for the majority of the Ojo Alamo Sandstone. F: representative pond/swamp floral locality AF1407 and the contact between earliest Paleocene Ojo Alamo Sandstone and early Paleocene Nacimiento Formation. G: close up of pond/swamp leaf locality AF1407 showing fine grained carbonaceous shales typical of pond/swamp floral facies