Time Travel And Causality

How would time travel affect causality? To be time travel, it would have to involve travel into the past which would mean an effect, arrival, preceding its cause, departure. This alone is enough to allow the first time travel paradox, circular causality, an earlier event both causing and caused by a later event. Anything else that happens depends on the nature of time.

In A Single Continuous Timeline

An effect precedes its cause, e.g., a time traveller arrives in the twenty-first century and will depart from the thirty-first century, although he experiences departure as preceding arrival.

In A Single Discontinuous Timeline

An effect prevents the event that would have been its cause, e.g., a time traveller with memories of having grown up in a thirty-first century civilization arrives in the twenty-first century but then prevents that remembered civilization from coming into existence. ("Memory" acquires a different or extended meaning.)

In Successive Timelines

An event in an earlier timeline causes an event in a later timeline, e.g., Neldorian time criminals from a timeline where Rome won the Second Punic War arrive in a timeline where they will help Carthage to win the Second Punic War. In this example, the words, "earlier" and "later," describe a temporal relationship between the two timelines, not a temporal relationship within either of the timelines.

I think that that covers most coherent options.