STRATIGRAPHIC MAPS Many varictics of stratigraphic maps have been developed, for partrayink diverse sorts of ecologic information. A thorough discussion of such maps may be found in Kumhein and SOAS - Simalucard and Sedimentation. We will limit ourselves lo ochly three map types: structure contour maps, 19opach maps, and facies inaps. The Curst Iwo are concerned with the external geometry of a 12 of rock, the third with its Quoposition. These three types of 112 pe are this mast commonly used in the cil and gas industry far mapping Turvoir systems Structure contour maps - these are rela lively slope in concepl, depicting the atulude of a single suitace top of a formation, for exailple) relative to a giver datul plante (company sea level Elevations of the surface are abtained from well lygs by knowing the well elevation and depth to the surface in question, one can calculate its elevation. The elevations are plaitted and contounod arithmetically, as an a topographic map. Structure contour maps are also read ike topographic maps - domes are closed elevations, basing are closed depressions, anticlines and Sundlines are linear elevations and depressions, faults involve superimposition of contour lines alcing a linear trend, and/or otsets a Corturs across the fault. Isapach Maps (isopachous contour maps) there are more complex because the contours record the thickness of a given unit at the point where it is mapped. Two clevations (top and base) are necessary to plof each point on the map. The thickness of the unit may be measured directly Love well data, or the thickness may be determined by using slucture contour 1912 put the top and base of the unit supach maps are useful in interpreting the behavior of arches and basins, especially the timing of textonic events relative to sedimentatian. TOT example, cratonic basins which subside during deposition commonly display ovate, concentric, isopach coulous, with grealest thickness in the basin center. Isopach maps are the most typical way of representing thickness variation of a reservoir or tlow urit. Reinerber is prach lines measure thicknGNIS, Tkit single surfaces Facies Maps - such maps are usually based on an isopach map of a given rock unil Conventional facies 112.ps are representations at the average composition of the unit at eact point platbed. That is at each point (usually a well, the total thicknesses of the various lithologies are recorded and expressed as a ratio cir percentage, which is then plotted. The most munur ratios ane sand shale and clastic nanclastic (normally carbonates, which can be combined in a lemmary diagramy, with sand, shale, and non-clastic normally carbonate) as the end-members The most common percentage Coloured in percent sandstorte (by thickness) as that is a coo l reservoir faces. Facies mape using these xunbined ratios are sometimes called rock inventory mapes: they depict the arcal distribution of all lithologies. Ratins are contoured, buat anturing must be done geometrically, that is, a ratio between any two components can vary from zero to infinity, while we usually plot three contours 8:1.1.1.1:8 lor 1:41: note then that a point on the 1:1 line should be equidistant from the 8:1 line on one side and the 1:8 line on the other. Once the Inlap is cxtured, it can be exskyred according tu tha subdivisions of the lithologic triangle: alo erprinting on the isopach bave map permits simultancnis inspection of both thickness and lithologic charge of the unit. Each stratigraphic column has been measured and the thicknesses of the sandsiones, Stiales, and linestunes as well as the tutal thickness have been recorded in the attached table. Table 1. The percent of cach lithogy in relation to the bestal thickness of the stratigraphic calumn Lic. 40 af sandstine in a 200' alumn is 20%) was also computed and recorded in the attached table. The clastic ratias (CR-thickness of clastics/thickness of non-clastics) and sand shale ralios (SSR-and-conglomerale/ sillslone shale) were delermined. I'rooddur: Plol your ratios and the lola thickness for each column on Figure 1. A convenient way of plotting ratios is to put then clown as CR/S-SR. In powerpoint contour the isonach Lasing a heavy black line and a 100 cuntiur interval. Also intour your clastic ratios with a blue line using values of 1/4, 1, and as your exintour interval; for your sand-shale ratic use a red line and values of 1, and II. Remember 1 is halfway in distance between 1/8 and when contouring. Refer to the lithologic triangle, Place the values of all contour intervals on the contour line (isopach and ratios). When you are doce, you will find contours of the ratios take tigether representa lithology. That is the intersection of the CR and S-SK tours block cut areas corresponding to areas in the lithologic triangle. Cesky your map in accordance with the triangle standard alar. and name the facies pret. Hints: Contour all your lines, ratios and isopachs as mechanically as possible; with so few citrul xirts it is best to draw the lines fairly straight. DONT ASSUME ANY CONTOURS ARE PARALLEL TO ANYTHING. In dealing with the ration, it is casiest to begin with the CR oxuntours and see if their areas are subdivided by the: 5 SR lines. Start with CR