The journal starts with the minutiae of daily life. Geologist skips ahead, find reference to a cave discovered across a mountain range. Strange artifacts and even stranger lifeforms found frozen in cave. Team takes back an artifact to study. As days progress, eerie things happen and people grow fearful.
Some people die in gruesome manner.
Communication to the outside is cut off. The captain valiantly keeps writing, until death is immediately at hand. You can then optionally place the people in the present, who have just finished reading the journal, in the same peril. Writers write about what they know, which is why so many characters are writers. Naturally the characters tend to have an extreme dedication to recording what happens, even as the seven-eyed, tentacled, pincered creature is about to fly in the bay window and devour them.