There is of course a good question why exactly you'd like to create a new finite element library in 2015 when there are already excellent ones out there. Smith And Wesson Model 25 Serial Numbers : Free Programs more. There's also the question why you would want to use Fortran in 2015 when that's simply not any more what the community believes is the language to use for new projects.

List of finite element software. Open source multiphysical simulation software developed by Finnish Ministry of Education's CSC, written primarily in Fortran.

But if you believe that you have good reasons for both of these questions, then it may be worthwhile looking into PLTMG -- the grandfather of all modern finite element libraries, and written in Fortran. As others have pointed out, PETSc also provides interfaces for Fortran and has finite element support built in. No, every evidence over the last ten years shows that neither of the two languages is more efficient than the other. And it isn't, in all practice, the language of modern scientific computing: all widely used software libraries that were started over the past 15 years are in fact written in C or C++. This is true for basically all finite element libraries, as well as packages such as PETSc and Trilinos. Codes that are still written in Fortran are overwhelmingly legacy codes that have been around since at least the 1980s.