Earth and Life Processes Discovered from Subseafloor Environments

Donna Blackman's research focuses on oceanic spreading centers, investigating how tectonics, mantle flow, and melting along ridge-transform systems vary and what that tells us about the underlying processes. A variety of geophysical methods are used in this research including mapping of seafloor morphology and geology, modeling of gravity data, and measuring subseafloor physical properties using ocean bottom seismographs, towed hydrophone streamers, and scientific drilling, coring and borehole logging. Computer simulations with colleagues test ideas on how deformation of the mantle and crust might occur. Slowly-spreading oceanic rift zones have recently been recognized to undergo episodes where the balance between magmatic and faulting activity evolves over time. During these 1-2 million year periods, newly formed seafloor develops unusual domal highs that are unroofed via long-lived faulting. Study of these 'oceanic core complexes' provides insight into what controls the magma-faulting balance so a major current focus of my research is to document their structure and, thereby, the processes that are responsible for their formation. Another research focus is how minerals develop a preferred orientation during slow viscous deformation in the deep Earth. Seismic waves propagate at different speeds through aligned versus randomly oriented mineral assemblages, so seismic data can detect subsurface deformation patterns induced by flow beneath the rigid tectonic plates. Mineral deformation modes differ depending on in-situ physical conditions and experimental data are still sparse. Numerical models can test the impact of various possible parameters to illuminate the range of outcomes that could occur in Earth's mantle. An aspect currently under study with colleages at Cornell and Paris is whether mineral alignment could result in strong directional dependence of viscosity, that could feedback and alter the style of upper mantle flow.Donna started her geologic studies in California (Pasadena City College and University of California Santa Cruz). She worked at the USGS Pacific Marine Geology Branch then moved to the eastern US for graduate school (MIT and Brown University). Postdoctoral work was completed at University of Washington and Scripps Institution of Oceanography. Since 1992, she has been a Research Geophysicist at Scripps, with a 1-yr interlude at Leeds University, U.K., in the mid-'90s. In 2012, she began a 3-year rotation at the US National Science Foundation, serving as a Program Director in the Marine Geology and Geophysics program.

• Preface1. Major Scientific Achievements of IODP (2003-2013): Overview and Highlights, K. Becker 2. New Frontiers of Subseafloor Life and the Biosphere 2.1. Exploration of Subseafloor Life and the Deep Biosphere through IODP (2003-2013), F. Inagaki, V. Orphan2.2. Biomass, Diversity and Metabolic Functions of Subseafloor Life(a) Detection and Enumeration of Microbial Cells, Y. Morono, J. Kallmeyer(b) Genetic Evidence of Subseafloor Microbial Communities, A. Teske, J. F. Biddle, M. A. Lever2.3. The Underground Economy: Energetic Constraints of Subseafloor Life, S. D'Hondt, G. Wang, A. J. Spivack2.4. Life at Subseafloor Extremes, K. Takai, K. Nakamura, D. LaRowe, J. P. Amend2.5. Life in the Oceanic Crust: Lessons from Subseafloor Laboratories, B. N. Orcutt, K. J. Edwards2.6. Cultivation of Subseafloor Prokaryotic Life, B. Engelen, H. Imachi2.7. Biogeochemical Consequences of the Sedimentary Subseafloor Biosphere, L. M. Wehrmann, T. G. Ferdelman3. Environmental Change, Processes and Effects3.1 New Insights from IODP (2003-2013), R. Stein3.2 Cenozoic Arctic Ocean Climate History: Some Highlights from the IODP Arctic Coring Expedition (ACEX), R. Stein, P. Weller, J. Backman, H. Brinkuis, K. Moran, H. Pälike 3.3 The Southern Ocean and Cenozoic Climate history, C. Escutia Dotti, et al.3.4 The Pacific Equatorial Age Transect: Cenozoic Ocean and Climate History, H. Pälike, M.W. Lyle, I. Raffi, H. Nishi3.5 North Atlantic Paleoceanography and Abrupt Climate Change, J.E.T. Channell, D.A. Hodell3.6 Coral reefs and Sea-level Change, G. Camoin, J. Webster4. Solid Earth Cycles and Geodynamics 4.1 Introduction, D. Blackman 4.2 Formation and Evolution of Oceanic Lithosphere4.2.1. New Insights on Oceanic Crustal Structure and Igneous Geochemistry, B. Ildefonse, N. Abe, M. Godard, D. Teagle, S. Umino4.2.2. Hydrologic Properties, Processes and Alteration in the Igneous Ocean, A. Fisher, W. Bach, J. Alt4.3 Large-scale and Long-term Volcanism on Oceanic Plates, W. Sager, A. Koppers4.4 Subduction Zones and Seismogenic Processes 4.4.1. Structure and Deformation History, H. Tobin, P. Henry, P. Vannuchi, L. Screaton4.4.2. Seismogenic Processes Revealed through the Nankai Trough Seismogenic Zone Experiments Core-Log-Geophysics and Observatories, M. Kinoshita, G. Kimura, S. Sato4.4.3. Fluid Origins, Thermal Regimes, and Fluid and Solute Fluxes in the Forearc of Subduction Zones, M. Kastner, E. Solomon5. Appendix: Summaries of IODP Expeditions 301-347, J. Lezius, R.SteinSubject index