What are those thin magenta lines on the Sectional / Terminal Area Chart near Death Valley?
Those lines denote areas of the MOA which have altitude exclusions different from what is listed on the chart's MOA table. In this case:


  MOA Excludes Airspace 3000' AGL &amp; Below


Notice the same style magenta lines are drawn in circles around airports in the MOA which also have the same style remark excluding a specific portion of the airspace.