Structural symbols such as fold, faults and strike and dip also appear in the legend. Oregon Geologic Map Examine your Oregon state geologic map and then answer the following questions. Locate the formation labeled Tcg in the north central part of the map. Map symbol Rock type Geologic age Relative age with respect to the large fold ad ad Complete the following maps by adding geologic contacts where appropriate. Next, add fold axes and identify the type of fold present.
Rock layers dip in the direction of the V made by the contacts when crossing a valley.
The strike of rock units generally parallels geologic contacts. Steep dipping rock layers will show a more narrow map outcrop than shallow dipping layers.