Viz Lab Summer Grant 2005

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Three-Dimensional Visualization of Late Triassic Landscape Evolution of South-Central Utah

Joseph Beer under Prof. Tim Demko, Geology

Research Synopsis

Field and well log data from central Utah identify three sequence bounding unconformities in the lower portion of the Chinle (Shinarump, Monitor Butte, Temple Mountain, and Moss Back Members) which function to divide these deposits into three periods of incision and subsequent valley fill. The initial period of degradation is marked by interfluve paleosols and truncation of the underlying Moenkopi Formation creating a paleovalley which constrains the deposition of these four members. The first paleovalley fill, represented by the Shinarump Member, is interpreted as a confined sandy low-sinuosity river system. A second period of incision is marked by truncation of the Shinarump and correlative paleosols and pedogenically modified strata. The Monitor Butte and correlative Temple Mountain Members overlie this unconformity and consist of mudstones and sandstones representing fluvio-lacustrine deposition and vertisols and interbedded mudstones and sandstones deposited in a high-sinuosity river system. A final cut and fill within the pre-Shinarump paleovalley is filled by the high- and low-sinuosity fluvial deposits of the Moss Back Member. Truncation of the Monitor Butte and Temple Mountain Members and the Moenkopi Fm. and interfluve pedogenesis mark the preceding surface of degradation. Erosional unconformities and correlative extensive pedogenesis within the Chinle in central Utah indicate a depositional history involving alternating periods of landscape degradation and aggradation. The tectonic setting of the Chinle basin within a dynamically subsiding back-arc basin may provide a mechanism for 1) uplift and erosion of Lower Triassic strata creating the master paleovalley surface, and 2) later subsidence of the Chinle depositional basin. The high frequency, low amplitude cut-and-fill nature of the lower portion of the Chinle is likely the result of changes in sediment flux and discharge as evidenced by detailed facies and pedogenic analysis, and paleoecological and paleoclimatic data. In addition, the nature of deposition within an incised valley network had a large affect on the accommodation, and the spatial distribution of facies preserved in the lower portion of the Chinle Formation.

Contributions Provided by the VDIL

As is likely evident after reading the above synopsis, the detailed nature of these findings necessitates the use of well thought-out diagrams and illustrations. The geologic history presented in this study includes interpretations of the sedimentology, paleopedology, paleoecology, paleoclimatology, paleolandscape evolution, and stratal architecture - all which vary through time. Clearly, in this case, a picture saying a thousand words ends up being utterly insufficient.

To solve this problem, an animation was created using Flash Mx during the summer and into the fall of 2005. This animation depicts the synchronous evolution of the paleolandscape and the deposition of the stratigraphy. The animation was well received by colleagues for several specific reasons:

1. Geologists, by nature, are deeply concerned with the time axis.

2. This project is specifically focused on time-based stratigraphic correlations. Unlike previous studies which correlate strata based upon similar depositional environments, this study recognizes the spatial diversity of the paleolandscape by correlating key surfaces which cut across a myriad of depositional and pedogenic environments.

3. The unique cut and fill nature of deposition of these strata is well suited for animated visualization because large amounts of strata were deposited and then subsequently removed prior to their preservation. As a result, a simple figure showing the resultant strata provides merely a subtle implication of those strata which were eroded prior to burial, whereas an animation can depict the deposition and distribution of all units regardless of their fate.

In conclusion I would like to thank the VDIL staff for helping teach me how to use both the hardware and software necessary to create an animation and I would like to encourage other researchers to take advantage of the opportunities provided by the VDIL to help visualize their findings.