A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Semicolon
Spelling
Part III. Style 20 spelling

A semicolon marks a greater break in the continuity of a sentence than does a comma. Use a semicolon in a compound sentence to separate independent clauses that are not connected by a coordinating conjunction (and, but, or, nor, yet, for, so).

One hundred communities are in various stages of completion; more are on the drawing board.

You can also use a semicolon with a coordinating conjunction if the clauses are long and have commas or other punctuation within them. In such cases, you probably should replace the semicolon with a period.

Although productivity per capita in U.S. industry is much more than that in China, China has an increasingly well educated young labor force; but the crucial point is that knowledge—which is transferable between peoples—has become the most important world economic resource.

Use a semicolon before the words then, however, thus, hence, indeed, accordingly, besides, and therefore when those words are used transitionally between two independent clauses.

Some think freedom always comes with democracy; however, many voters in many countries have voted for governments that they know will restrict their rights.

When items in a series have internal punctuation, separate them with semicolons (see also 21.2.2).

Green indicates vegetation that remained stable; red, vegetation that disappeared; yellow, new vegetation.