Lesli J. Wood

Lecture LW1: Deltas on Mars: A Martian History of Standing Water and Moving Sediments

New satellite imagery from Mars is revolutionizing our knowledge of the geomorphology of this planet. Although Rovers Opportunity and Spirit provide “ground truth” on the planet’s surface, much can be learned from quantitative analysis of the spectacular images pouring from the satellites, Global Surveyor and the Mars Express that orbit the planet. Geomorphic elements associated with flowing water are everywhere on Mars. These elements include debris flows, gullies, debris aprons, all manner of drainage networks, erosional shadows, deltas and deltaic distributaries. One such delta, the Eberswalde Delta is examined in detail in this talk. The delta is composed of six separate phases of lobe development and appears to have prograded some 17 km from the apex. Cross-cutting distributary relationships and compensated deposition of lobes are clearly visible. Sinuosity, radius of channel curvature, meander bend width, and channel width parameters are examined for several lobe systems. Channel sinuosities vary between 1.2 – 1.8, defined by Schumm (1968) as low to moderate sinuosity systems typical of those transporting bed or mixed loads. There appears to be some convergence between age and sinuosity, however some of the younger systems show specific reaches of increased sinuosity associated with abutment against resistant beds of older lobes. This affect of older deposits on the morphology of the channels suggests that these older lobes were fairly well indurated prior to the deposition of the youngest progradational lobes. 86% of distributaries in the Eberswalde Delta are 100-240 meters wide. This number compares with 62% and 44% in the Atchafalya and Wax Lake Deltas of Louisiana, respectively, although the martian delta nearly 14X larger than these two deltas. Such small distributaries may indicate lower average and shorter duration flows in the Mars distributaries than those typical of the wetter Gulf Coast deltas. However, the volume of the material in the Mars deltas suggests long periods of activity and sediment transport. It is probable that this delta formed under rather ephemeral flow conditions, with distributaries that were intermittently active transporting a bed-to-mixed load of relatively coarse-grained sediments. The lobes prograded well out into a standing body of water, possibly in response to fluctuations or regressing water level. Further work should better quantify the flow conditions and history of this delta and numerous other deltaic and alluvial features that have been identified on the martian surface.

Lecture LW2: Quantitative Seismic Geomorphology: Visualizing the future of paleo-landscape research

Seismic geomorphology; the technique of extracting of geomorphic insights using predominantly 3D seismic data, is a rapidly evolving discipline that facilitates the study of the subsurface, using plan view images. A variety of analytical techniques are employed to image and visualize depositional elements and other geologically significant features. Likewise over a century of study of modern geomorphic systems and processes enable empirical relationships to be derived from study of reservoir morphologies in seismic data. This technique offers the geoscientist new data to add to their interpretation and renders a detail of spatial understanding unafforded through the study of outcrops, wells and core. We will look at several case studies in Indonesia, Morocco and Eastern Mexico, in both deep water and shallow water systems and examine the manner in which these insights can be applied to better understand those issues which will affect the exploration and development success of similar deposits. Fluvial deltaic deposits in Indonesia and the Gulf of Mexico show strong correlation between morphology and lithology, as well as the influence of regional tectonics on reservoir orientations. Deep water mass failure deposits are understudy in areas around the world to better understand the processes that control sediment movement from shelf edge to slope to basin floor, as well as the hazards associated with exploration in these boundary zones between shallow and deep water. In addition, seismic analysis of paleo-drainage systems and their deposits offers opportunity to impact proxies of climate change. Current work underway in Indonesia is being used to assess South Asian paleo-monsoonal magnitudes and frequencies. .

Wood, L. J., 2007, Quantitative seismic geomorphology of Pliocene and Miocene fluvial systems in the northern Gulf of Mexico, U.S.A.: Journal of Sedimentary Research, v. 77, p. 713–730.

Wood, L. J., 2006, Quantitative geomorphology of the Mars Eberswalde Delta: Geological Society of America Bulletin, v. 118, no. 5/6, p. 557–566.

Wood, L. J., 2004, Chapter 3. Predicting tidal sand reservoir architecture using data from modern and ancient depositional systems, in Grammer, G. M., Harris, P. M., and Eberli, G. P., eds., Integration of outcrop and modern analogs in reservoir modeling: American Association of Petroleum Geologists, AAPG Memoir 80, p. 45–66.