Sentence:  The reason is that because strata are not unlimited in the horizontal direction and moreover are not horizontal, they may well come up against strata of a different age simply as a result of lateral displacement. The <WSD>'lateralists</WSD>' have frequently pointed this out in relation to the history of the San Andreas fault. 
Meaning of the word marked with <WSD> tags:  One who favors a lateral approach or explanation over one that involves a different direction.