Lake Tahoe References
Babcock, Heather, ????, Geology and Natural History of Lake Tahoe. http://ceres.ca.gov/tcsf/tahoe-local/geology.html
GeoMapApp. http://www.geomapapp.org
Lopez, Christopher T., Schweickert, Richard A., Lahren, Mary M., Howle, Jim, Kitts, Christopher, Ota, Jeffrey M., and Richards, Bob, 2004, Submarine Geology Within the Western Part of Lake Tahoe, California, GSA Bull.
Reisewitz, Annie, 2009, Scripps Studies Offer New Picture of Lake Tahoe’s Earthquake Potential: Scripps Institution of Oceanography/University of California, San Diego. http://ucsdnews.ucsd.edu/newsrel/science/04-09RenoQuake.asp
Schweickert, ????, R.A., Moore, J.G., Lahren, M.M., Lopez, C., Howle, J.F., Kitts, C., and Ota, J. Lake Tahoe Submarine Geology: Implications for Ancestral Lake, Landslides, and Faults. GSA Bull.
USGS. Selected Oblique Views of Lake Tahoe, CA-NV. http://walrus.wr.usgs.gov/pacmaps/lt-persp.html
Thursday, March 25, 2010
Figure 6: Boulder debris-flow and slope apron
View to west of western part of lake. Boulder-sized clasts in fan-shaped subaqueous debris flow in foreground, and subaqueous slope apron on steeper gradient in background. I would suspect that the debris flow deposits bypassed the apron. This is a quite large debris flow, possibly the result of tectonics or possibly glacial ice damming (see Schweickert, ???? for further discussion of debris flows in Lake Tahoe).
View to west of western part of lake. Boulder-sized clasts in fan-shaped subaqueous debris flow in foreground, and subaqueous slope apron on steeper gradient in background. I would suspect that the debris flow deposits bypassed the apron. This is a quite large debris flow, possibly the result of tectonics or possibly glacial ice damming (see Schweickert, ???? for further discussion of debris flows in Lake Tahoe).
Figure 5: Paleo-shoreline terrace with subaqueous debris flow.
NW corner of lake. 20 ft contour interval. Subaqueous shoreline terrace which may be the site of deltaic deposition as a shallow shelf. This is evidence of a previously lower lake level. A deep subaqueous debris flow occurs to the right, which may indicate a tectonic event, such as a pulse of uplift, earthquake, etc, or sudden influx of sediments/water by means of climatic increase in humidity.
NW corner of lake. 20 ft contour interval. Subaqueous shoreline terrace which may be the site of deltaic deposition as a shallow shelf. This is evidence of a previously lower lake level. A deep subaqueous debris flow occurs to the right, which may indicate a tectonic event, such as a pulse of uplift, earthquake, etc, or sudden influx of sediments/water by means of climatic increase in humidity.
Figures 1 - 4: Lake Tahoe, California-Nevada border, Western US
Shaded colors of satellite topography indicate elevation. 100 ft contour interval. The blue shaded region in Fig. 1 indicates lake surface. Fig. 2 is a bathymetric map of the lake. Drainage basin divides running roughly N-S are likely border faults. The eastern margin is much steeper than the western margin (Fig. 2-4). Abundant fluvial valleys exist on the western margin and on the southern (rift-axial) margin, and are not as abundant on eastern steep margin. Core and submersible data suggest that an extensive lacustrine system existed in the western part of the lake during Late Pliocene to Late Pleistocene, prior to the formation of the modern depocenter (Lopez, 2004). The northern margin is composed of andesitic intrusions following faults, which bisected and dammed a northern fluvial valley (Babcock). During glacial periods, the southern fluvial system was periodically dammed causing fluctuations of lake level of as much as 800 feet above modern lake level (Babcock). Ice-damming in several bays is attributed to be the cause for some boulder-sized debris flows (Babcock).
Shaded colors of satellite topography indicate elevation. 100 ft contour interval. The blue shaded region in Fig. 1 indicates lake surface. Fig. 2 is a bathymetric map of the lake. Drainage basin divides running roughly N-S are likely border faults. The eastern margin is much steeper than the western margin (Fig. 2-4). Abundant fluvial valleys exist on the western margin and on the southern (rift-axial) margin, and are not as abundant on eastern steep margin. Core and submersible data suggest that an extensive lacustrine system existed in the western part of the lake during Late Pliocene to Late Pleistocene, prior to the formation of the modern depocenter (Lopez, 2004). The northern margin is composed of andesitic intrusions following faults, which bisected and dammed a northern fluvial valley (Babcock). During glacial periods, the southern fluvial system was periodically dammed causing fluctuations of lake level of as much as 800 feet above modern lake level (Babcock). Ice-damming in several bays is attributed to be the cause for some boulder-sized debris flows (Babcock).
High-resolution bathymetric maps of Lake Tahoe provide a unique glimse at the subaerial and subaqueous nonmarine depositional systems in a half graben. This enables an examination of the relationships between gradient of a lake basin margin and depositional systems. Furthermore, many perched shorelines both subaerial and subaqueous preserve a record of lake-level fluctuation. Bathymetry of lakefloor is useful in that previous studies Lake Tahoe geology involved (subaerial) geologic mapping and core data.
Lake Tahoe lies within an asymmetrical half-graben, within the Basin-and-Range continental rift system of Western US. The lake basin has changed through time as a result of tectonic and climatic processes. Tectonic processes include rift-related faulting and magmatism. The region experiences magnitude 7.0 earthquakes (Reisewitz), which could produce debris flows. The lake responded to climatic forcing and glaciations by expanding and contracting.
Lake Tahoe lies within an asymmetrical half-graben, within the Basin-and-Range continental rift system of Western US. The lake basin has changed through time as a result of tectonic and climatic processes. Tectonic processes include rift-related faulting and magmatism. The region experiences magnitude 7.0 earthquakes (Reisewitz), which could produce debris flows. The lake responded to climatic forcing and glaciations by expanding and contracting.
Tuesday, February 23, 2010
The following link is a form for rock sample inventory of samples collected in NW China.
Rock Sample Form
Rock Sample Form
Wednesday, February 17, 2010
Additional References
Regional Geology
Allen, M B; Sengor, A M C; Natal'in, B A, 1995, Junggar, Turfan and Alakol basins as Late Permian to ?Early Triassic extensional structures in a sinistral shear zone in the Altaid orogenic collage, Central Asia: Journal of the Geological Society of London, vol.152, Part 2, pp.327-338.
Carroll, A.R., Graham, S.A., Hendrix, M.S., Ying, D., Zhou, D., 1995, Late Paleozoic tectonic amalgamation of northwestern China: Sedimentary record of the northern Tarim, northwestern Turpan, and southern Junggar Basins: GSA Bull., v. 107, p. 571-594.
Greene, T.J., Carroll, A.R., Wartes, M., Graham, S.A., Wooden, J.L., 2005, Integrated provenance analysis of a complex orogenic terrane: Mesozoic uplift of the Bogda Shan and inception of the Turpan-Hami Basin, NW China: Journal of Sedimentary Research, v. 75, p. 251-267.
Hendrix, M.S., 2000, Evolution of Mesozoic sandstone compositions, southern Junggar, northern Tarim, and western Turpan basins, northwest China: a detrital record of the ancestral Tian Shan: Journal of Sedimentary Research, v. 70, p. 520-532.
Sengor, A.M.C., and Natal’in, B.A., 1996, Paleotectonics of Asia: fragments of a synthesis, in Yin, A. and Harrison, T.M. (eds.), The tectonic evolution of Asia: Cambridge University Press, New York, p. 486-640.
Shao, L., Stattegger, K., and Garbe-Schoenberg, C-D., 2001, Sandstone petrology and geochemistry of the Turpan Basin (NW China): Implications for the tectonic evolution of a continental basin: Journal of Sedimentary Research, v. 71, p. 37-49.
Wartes, M.A. Carroll, A.R., Greene, T.J., 2002, Permian sedimentary record of the Turpan-Hami Basin and adjacent regions, Northwest China; constraints on postamalgamation tectonic evolution: Geological Society of America Bulletin, vol.114, p.131-152.
Yang, W., Liu, Y.Q., Feng, Q., Lin, J.Y., Zhou, D.W., and Wang, D., 2007, Sedimentary evidence on Early to Late Permian mid-high latitude continental climate variability, southern Bogda Mountains, NW China: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 252, p. 239-258.
Yin, A. and Nie, S., 1996, A Phanerozoic palinspastic reconstruction of China and its neighboring regions, in Yin, A. and Harrison, T.M. (eds.), The tectonic evolution of Asia: Cambridge University Press, New York, p. 485.
Lacustrine Depositional Environments
Alonso-Zarza, Ana M., 2002, Palaeoenvironmnetal significance of palustrine carbonates and calcretes in the geological record: Earth-Science Reviews, v. 60, p. 261-298.
Carroll, A.R., and Bohacs, K.M., 1999, Stratigraphic classification of ancient lakes—balancing tectonic and climatic controls: Geology, v. 27, p. 99-102.
Talbot, M.R., and Allen, P.A., 1996, Lakes, in Reading, H.G., ed., Sedimentary environments: processes, facies and stratigraphy: Blackwell Science, London, p. 83-124.
Rift basin structural-stratigraphic architecture
Lambiase, J.J., 1990, A model for tectonic control of lacustrine stratigraphic sequences in continental rift basins, in Katz, M.J., ed., Lacustrine Basin Exploration—Case Studies and Modern Analogs: American Association of Petroleum Geologists, Memoir 50, p. 265-276.
Olsen, 1990, Tectonic, Climatic, and Biotic Modulation of Lacustrine Ecosystems—Examples from Newark Supergroup of Eastern North America, in Katz, B., ed., Lacustrine Basin Exploration—Case Studies and Modern Analogs: American Association of Petroleum Geologists, Memoir 50, p. 209-224.
Withjack, Martha O., and Schlische, Roy W., and Olsen, Paul E., 2002, Rift-basin Structure and its Influence on Sedimentary Systems, SEPM Special Publication No. 73, Sedimentation in Continental Rifts, p. 57-81.
Analog basins - Newark Basin
Schlische, R.W., 1992, Structural and stratigraphic development of the Newark extensional basin, eastern North America—implications for the growth of the basin and its bounding structures: Geological Society of America, Bulletin, v.104, p. 1246-1263.
Schlische, R.W., 1993, Anatomy and Evolution of the Triassic-Jurassic Continental Rift System, Eastern North America, Tectonics, v. 12, no. 4, p.1026-1042.
Smoot, J.P., 1991. Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America. Palaeogeography, Palaeoclimatology, Palaeoecology, 84: p. 369-423.
Allen, M B; Sengor, A M C; Natal'in, B A, 1995, Junggar, Turfan and Alakol basins as Late Permian to ?Early Triassic extensional structures in a sinistral shear zone in the Altaid orogenic collage, Central Asia: Journal of the Geological Society of London, vol.152, Part 2, pp.327-338.
Carroll, A.R., Graham, S.A., Hendrix, M.S., Ying, D., Zhou, D., 1995, Late Paleozoic tectonic amalgamation of northwestern China: Sedimentary record of the northern Tarim, northwestern Turpan, and southern Junggar Basins: GSA Bull., v. 107, p. 571-594.
Greene, T.J., Carroll, A.R., Wartes, M., Graham, S.A., Wooden, J.L., 2005, Integrated provenance analysis of a complex orogenic terrane: Mesozoic uplift of the Bogda Shan and inception of the Turpan-Hami Basin, NW China: Journal of Sedimentary Research, v. 75, p. 251-267.
Hendrix, M.S., 2000, Evolution of Mesozoic sandstone compositions, southern Junggar, northern Tarim, and western Turpan basins, northwest China: a detrital record of the ancestral Tian Shan: Journal of Sedimentary Research, v. 70, p. 520-532.
Sengor, A.M.C., and Natal’in, B.A., 1996, Paleotectonics of Asia: fragments of a synthesis, in Yin, A. and Harrison, T.M. (eds.), The tectonic evolution of Asia: Cambridge University Press, New York, p. 486-640.
Shao, L., Stattegger, K., and Garbe-Schoenberg, C-D., 2001, Sandstone petrology and geochemistry of the Turpan Basin (NW China): Implications for the tectonic evolution of a continental basin: Journal of Sedimentary Research, v. 71, p. 37-49.
Wartes, M.A. Carroll, A.R., Greene, T.J., 2002, Permian sedimentary record of the Turpan-Hami Basin and adjacent regions, Northwest China; constraints on postamalgamation tectonic evolution: Geological Society of America Bulletin, vol.114, p.131-152.
Yang, W., Liu, Y.Q., Feng, Q., Lin, J.Y., Zhou, D.W., and Wang, D., 2007, Sedimentary evidence on Early to Late Permian mid-high latitude continental climate variability, southern Bogda Mountains, NW China: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 252, p. 239-258.
Yin, A. and Nie, S., 1996, A Phanerozoic palinspastic reconstruction of China and its neighboring regions, in Yin, A. and Harrison, T.M. (eds.), The tectonic evolution of Asia: Cambridge University Press, New York, p. 485.
Lacustrine Depositional Environments
Alonso-Zarza, Ana M., 2002, Palaeoenvironmnetal significance of palustrine carbonates and calcretes in the geological record: Earth-Science Reviews, v. 60, p. 261-298.
Carroll, A.R., and Bohacs, K.M., 1999, Stratigraphic classification of ancient lakes—balancing tectonic and climatic controls: Geology, v. 27, p. 99-102.
Talbot, M.R., and Allen, P.A., 1996, Lakes, in Reading, H.G., ed., Sedimentary environments: processes, facies and stratigraphy: Blackwell Science, London, p. 83-124.
Rift basin structural-stratigraphic architecture
Lambiase, J.J., 1990, A model for tectonic control of lacustrine stratigraphic sequences in continental rift basins, in Katz, M.J., ed., Lacustrine Basin Exploration—Case Studies and Modern Analogs: American Association of Petroleum Geologists, Memoir 50, p. 265-276.
Olsen, 1990, Tectonic, Climatic, and Biotic Modulation of Lacustrine Ecosystems—Examples from Newark Supergroup of Eastern North America, in Katz, B., ed., Lacustrine Basin Exploration—Case Studies and Modern Analogs: American Association of Petroleum Geologists, Memoir 50, p. 209-224.
Withjack, Martha O., and Schlische, Roy W., and Olsen, Paul E., 2002, Rift-basin Structure and its Influence on Sedimentary Systems, SEPM Special Publication No. 73, Sedimentation in Continental Rifts, p. 57-81.
Analog basins - Newark Basin
Schlische, R.W., 1992, Structural and stratigraphic development of the Newark extensional basin, eastern North America—implications for the growth of the basin and its bounding structures: Geological Society of America, Bulletin, v.104, p. 1246-1263.
Schlische, R.W., 1993, Anatomy and Evolution of the Triassic-Jurassic Continental Rift System, Eastern North America, Tectonics, v. 12, no. 4, p.1026-1042.
Smoot, J.P., 1991. Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America. Palaeogeography, Palaeoclimatology, Palaeoecology, 84: p. 369-423.
Selected References
1. Carroll, A.R., and Bohacs, K.M., 1999, Stratigraphic classification of ancient lakes—balancing tectonic and climatic controls: Geology, v. 27, p. 99-102.
Climatic and tectonic controlling processes affect the depositional facies and sequences of lake deposits, resulting in either under-, balance-, or over-filled lake basins. Each type of lake exhibits a distinct suite of lithofacies, stacking patterns, and depositional systems. The lake type is a result of the balance between relative climatic humidity, measured in net precipitation (or P/E), and the amount of basin subsidence. This may be useful in interpreting the climatic and tectonic processes controlling cycle/sequence development based on sedimentary evidence. Such interpretations will enable a more accurate process-response time-stratigraphic correlation.
2. Withjack, Martha O., and Schlische, Roy W., and Olsen, Paul E., 2002, Rift-basin Structure and its Influence on Sedimentary Systems, SEPM Special Publication No. 73, Sedimentation in Continental Rifts, p. 57-81.
Rift-related structural features impact basin topography throughout various stages of continental rift development, and sedimentary depositional systems are created in response. Thus, the tectonic history of a rift basin may be reconstructed based on sedimentary evidence. This may be useful in reconstructing tectonic history of a basin where rift-related structural features are either absent, unidentified, or overprinted—all of which apply to the study area I am working on. Lucaogou (LCG) and Hongyanchi (HYC) Fms. represent the dominantly-lacustrine deposits of the Permo-Triassic strata in the study area, indicating deposition during late rifting phase. Perhaps the enigmatic boundary between LCG and HYC represents a major episode or pulse of basin tectonism.
3. Allen, M B; Sengor, A M C; Natal'in, B A, 1995, Junggar, Turfan and Alakol basins as Late Permian to ?Early Triassic extensional structures in a sinistral shear zone in the Altaid orogenic collage, Central Asia: Journal of the Geological Society of London, vol.152, Part 2, pp.327-338.
The Turpan-Hami Basin was formed in a structurally complex area. During early Permian time, large, parallel, E-W trending strike-slip faults developed along older Altaid suture zone structures. This initiated the development of a broad (>1000 km) sinistral shear zone between two large cratons, within which NW-SE extension produced a series of half-grabens. The reason I list this reference is the following: does anyone know of a modern or ancient analog for this tectonic setting?
4. Talbot, M.R., and Allen, P.A., 1996, Lakes, in Reading, H.G., ed., Sedimentary environments: processes, facies and stratigraphy: Blackwell Science, London, p. 83-124.
Ancient lake deposits are as complex as their modern equivalents. A brief summary is presented of modern lacustrine depositional environments—useful for interpreting ancient lake deposits and their controlling climatic and tectonic processes. However, caution must be exercised when interpreting controlling processes due to the complexities of modern lakes. For example, the case of a rift valley in Utah where two lakes occur in the same climate zone but only one of those lakes is hypersaline.
5. Yang, W., Liu, Y.Q., Feng, Q., Lin, J.Y., Zhou, D.W., and Wang, D., 2007, Sedimentary evidence on Early to Late Permian mid-high latitude continental climate variability, southern Bogda Mountains, NW China: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 252, p. 239-258.
Preliminary results indicate LCG and HYC were deposited during a time of extreme climatic variability. This highlights the importance of differentiating between interpreted climatic and tectonic processes controlling the development of depositional systems and their stacking, and in differentiating those allogenic processes with autogenic sedimentary processes. This is critical for a more accurate process-response time-stratigraphic correlation, and in understanding whether the boundary separating LCG and HYC is dominantly a climatic cause, dominantly tectonic, or a combination of both.
Climatic and tectonic controlling processes affect the depositional facies and sequences of lake deposits, resulting in either under-, balance-, or over-filled lake basins. Each type of lake exhibits a distinct suite of lithofacies, stacking patterns, and depositional systems. The lake type is a result of the balance between relative climatic humidity, measured in net precipitation (or P/E), and the amount of basin subsidence. This may be useful in interpreting the climatic and tectonic processes controlling cycle/sequence development based on sedimentary evidence. Such interpretations will enable a more accurate process-response time-stratigraphic correlation.
2. Withjack, Martha O., and Schlische, Roy W., and Olsen, Paul E., 2002, Rift-basin Structure and its Influence on Sedimentary Systems, SEPM Special Publication No. 73, Sedimentation in Continental Rifts, p. 57-81.
Rift-related structural features impact basin topography throughout various stages of continental rift development, and sedimentary depositional systems are created in response. Thus, the tectonic history of a rift basin may be reconstructed based on sedimentary evidence. This may be useful in reconstructing tectonic history of a basin where rift-related structural features are either absent, unidentified, or overprinted—all of which apply to the study area I am working on. Lucaogou (LCG) and Hongyanchi (HYC) Fms. represent the dominantly-lacustrine deposits of the Permo-Triassic strata in the study area, indicating deposition during late rifting phase. Perhaps the enigmatic boundary between LCG and HYC represents a major episode or pulse of basin tectonism.
3. Allen, M B; Sengor, A M C; Natal'in, B A, 1995, Junggar, Turfan and Alakol basins as Late Permian to ?Early Triassic extensional structures in a sinistral shear zone in the Altaid orogenic collage, Central Asia: Journal of the Geological Society of London, vol.152, Part 2, pp.327-338.
The Turpan-Hami Basin was formed in a structurally complex area. During early Permian time, large, parallel, E-W trending strike-slip faults developed along older Altaid suture zone structures. This initiated the development of a broad (>1000 km) sinistral shear zone between two large cratons, within which NW-SE extension produced a series of half-grabens. The reason I list this reference is the following: does anyone know of a modern or ancient analog for this tectonic setting?
4. Talbot, M.R., and Allen, P.A., 1996, Lakes, in Reading, H.G., ed., Sedimentary environments: processes, facies and stratigraphy: Blackwell Science, London, p. 83-124.
Ancient lake deposits are as complex as their modern equivalents. A brief summary is presented of modern lacustrine depositional environments—useful for interpreting ancient lake deposits and their controlling climatic and tectonic processes. However, caution must be exercised when interpreting controlling processes due to the complexities of modern lakes. For example, the case of a rift valley in Utah where two lakes occur in the same climate zone but only one of those lakes is hypersaline.
5. Yang, W., Liu, Y.Q., Feng, Q., Lin, J.Y., Zhou, D.W., and Wang, D., 2007, Sedimentary evidence on Early to Late Permian mid-high latitude continental climate variability, southern Bogda Mountains, NW China: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 252, p. 239-258.
Preliminary results indicate LCG and HYC were deposited during a time of extreme climatic variability. This highlights the importance of differentiating between interpreted climatic and tectonic processes controlling the development of depositional systems and their stacking, and in differentiating those allogenic processes with autogenic sedimentary processes. This is critical for a more accurate process-response time-stratigraphic correlation, and in understanding whether the boundary separating LCG and HYC is dominantly a climatic cause, dominantly tectonic, or a combination of both.
Thursday, January 28, 2010
The Tarlong Valley Blog
Welcome to the Tarlong Valley Blog!
The theme of this blog pertains to my ongoing thesis research of cyclic Permian fluvial and lacustrine deposits of NW China. The focus of the research is reconstructing stratigraphic architecture and basin-fill history of nonmarine deposits in a half-graben. The location of study is in the beautiful and remote Tarlong Valley, in the southern foothills of the Bogda Mountains, Xinjiang, NW China.
I am currently focusing on the nature and origins of a nonmarine cycle boundary in a half-graben. A nonmarine stratigraphic boundary where major facies shifts occur indicates drastic changes in environmental conditions, but may have highly variable magnitude of facies shifts in different parts of a half-graben due to rapid lateral facies changes, common autogenic processes, and irregular topography. This hypothesis is tested using the boundary separating lower Permian Lucaogou and Hongyanchi low-order cycles in Tarlong-Taodonggou half graben, which covers 88 km2. Superbly exposed sections were measured in the summer of 2009 of the boundary. The boundary shows variable facies juxtapositions on 5 sections 0.2-5 km apart. Complex facies relationships in the NE signify the control by local fluvial valley topography. Understanding autogenic and allogenic processes and basin topography is critical to correlating stratigraphic boundaries in n onmarine time-stratigraphic analysis.
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