Basin Analysis

I. Intro A. Basin analysis= detailed integrated study of sed. rocks 1. must consider sedimentary basin as a whole 2. important for geologic history & economic considerations

II. What is a Basin A. Sedimentary basins = areas where Earth's crust dominated by subsidence B. Sediment in basin accumulates to > 10 km C. Deepest basin > 15km (Caspian & Gulf of Mexico Map © MBARI 2006

usgs Figure 1. Index map of the Los Angeles basin region. The red- dashed rectangle in the center of the map locates the Whittier fault and our northeastern Los Angeles basin study area. Lines A-A', B-B' and C-C' are the locations of cross sections in Figures 2, 3 and 4. The red stars are the epicenters of important recent earthquakes in the area. Figure 2. Miocene turbidite fan-channel sandstones are productive in the footwall block block of the Whittier fault on the steeply-dipping south flank of the Puente Hills anticline. Stratigraphically controlled oil accumulations in Pliocene rocks are present in the footwall syncline east and west of the cross section. Over 3 MMBO have been produced since 1880 from fractured Upper Miocene La Vida shale, Middle Miocene Topanga sandstone and Jurassic basement rocks on the crest of the Puente Hills anticline

III. Source and Direction of Transport A. Examine seds for provenance B. Examine sed structures for paleocurrent analysis

C. Incorporate provenance & paleocurrent data for reconstruction of drainage direction 1. conglomerates important 2. proportion of quartz, feldspar, lithic fragments important i. caution diagenesis may alter composition 3. heavy mineral suite also important i. kyanite, sillimanite, andalusite = ii. tourmaline, beryl, topaz = pegmatites 4. also use textures pangea.stanford.edu/research/noble/epdu/paper / pangea.stanford.edu/research/noble/epdu/paper /

D. Paleocurrent analysis requires 100's of measurements 1. currents vary in environment 2. must correct for dip FIGURE 3.—Distribution of the Copper Harbor Conglomerate and paleocurrent directions on the Northern Peninsula of Michigan: 1, average direction of current flow from crossbeds in conglomeratic sandstone. 2, average direction of current flow from cross-beds in "red facies" 3, direction of current flow indicated by imbrication of pebbles. Number of individual observations included in average is shown by each arrow, Modified from White and Wright (1960

IV. Stratigraphic diagrams A. 2D = stratigraphic cross-section 1. must be corrected for structure 2. shows lateral facies variations B. 3D = fence diagram 1. Data from wells/measured sections 2. can be complex, lose detail

V. Structure Contour Maps A. Similar to topographic map 1. surface contoured is surface of key unit 2. need many data points f

VI. Lithofacies Map A. Shows variation of some aspect of a stratigraphic unit B. Also have biofacies maps / Shell Oil