Geographical error in the Silmarillion?

Question

The following passage makes no sense:

for nigh and two years after the Dagor Bragollach the Noldor still defended the western pass about the sources of Sirion, for the power of Ulmo was in that water, and Minas Tirith withstood the orcs.

This makes no sense because Sirion is in the middle of Beleriand, and according to The Lord of the rings map, Minas Tirith is in the south-east, near Mordor. Were there two towers named Minas Tirith? Or is this passage legitimately referencing first the river, and then tower near Mordor?

Answer 1

Yes; according to The Silmarillion,

Between Dorthonion and the Shadowy Mountains there was a narrow vale, whose sheer walls were clad with pines; but the vale itself was green, for the River Sirion flowed through it, hastening towards Beleriand. Finrod held the Pass of Sirion, and upon the isle of Tol Sirion in the midst of the river he built a mighty watch-tower, Minas Tirith; but after Nargothrond was made he committed that fortress mostly to the keeping of Orodreth his brother.

(The Silmarillion, Chapter 14, "Of Beleriand And Its Realms")

Thus, this Minas Tirith was indeed "about the sources of Sirion".

Answer 2

Minas Tirith was a castle on the Isle of Tol Sirion built to defend the passes of Sirion by the Echoriath in the first age.

Minas Tirith was also another name for Minas Anor which we know from the Lord of the rings. Two Totally different fortresses albeit both attacked and assaulted by Sauron

http://lotr.wikia.com/wiki/Beleriand?file=Map_of_Beleriand.jpg

Look for Tol Sirion in the gap between Hithlum and Dorthonion at the other end of the pass to the Fen of Serech

The LOTR Minas Tirith was built in the late 2nd Age around 3 and a half thousand years after the Original was destroyed when Luthien and Huan defeated Sauron to rescue Beren

Answer 3

And now, eight years later, I will add that Minas Tirith simply translates through Westron into English as Tower of Guard. It's a name that easily could be repeated; and in Tolkien's self-characterized legendarium was, millennia apart.