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Abstract:
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The eastern side of the Guadalupe Mountains , located in New Mexico and west Texas , represents an erosional profile along the Capitan reef margin . A complete shelf -to -basin exposure of the Upper Permian Capitan shelf margin is found on the north wall of North McKittrick Canyon , which is nearly perpendicular to the Capitan reef margin . An excellent 2 -D sequence stratigraphic framework for upper Permian backreef facies has been developed by previous workers for North McKittrick Canyon (Tinker , 1998 ) and Slaughter Canyon (Osleger , 1998 ) , forming the basis for observations in this study .
The goal of this study is to describe the sequence stratigraphic architecture of the Yates Formation , focusing on the Y4 -Y6 high -frequency sequences (HFSs ) found in the middle to outer shelf depositional systems , and to illustrate the use of airborne lidar data to quantitatively map at the cycle -scale . Seven measured sections were taken in North McKittrick Canyon . From airborne lidar , 3 -D geometries of key sedimentary and structural features were mapped in Polyworks , in addition to the sequence boundaries delineating the Yates 4 -6 HFSs .
In general , major cycles exhibit asymmetry and shoal upward . Cycle boundaries are sometimes hard to delineate due to amalgamation , particularly in the shelf crest . High -frequency sequences are commonly asymmetric ; they deepen and thicken upward toward the maximum flooding surface , and the boundaries between HFSs are usually marked by thick siltstones . Major HFS boundaries can be mapped across the entire dataset , and some component cycles can be observed for minimum distances of one kilometer in an updip -downdip direction . Also , some facies tract dimensions can be estimated directly from the lidar data . Measured sections indicate that the shelf crest facies tract shifts seaward with each successive HFS , while the outer shelf facies tract steps landward .
Future work that could be done with the Y4 -Y6 HFSs includes 8 -10 more measured sections , collection of samples for thin sections , and tracing out of contacts between facies tracts . Extensive lidar data interpretation needs to be done so that digital outcrop models demonstrating facies distributions can be produced . This would enable the development of an outcrop analog model to mixed carbonate -siliciclastic reservoirs , which would be unprecedented in this area . |