Sentential Clauses :

Some relative clauses will refer to more than a single word in the preceding text; they can modify an entire clause or even a series of clauses.

• Charlie didn't get the job in administration, which really surprised his friends.
  
  
  
• Charlie didn't get the job in administration, and he didn't even apply for the Dean's position, which really surprised his friends.

A relative clause that refers to or modifies entire clauses in this manner is called a sentential clause. Sometimes the "which" of a sentential clause will get tucked into the clause as the determiner of a noun:

Charlie might very well take a job as headmaster, in which case the school might as well close down.