I ran 69 min for a 1/2 and this was definitely at a pace above my LT, which was ~5:30 pace. Marathon pace is generally just slightly faster than LT pace. One has to remember that the pace at LT doesn't result in any net increase in lactate. It is the intensity above the LT wherein lactate becomes an issue.
The thing I find interesting in the discussion of the LT is that a lot of individuals give the impression that that this is an "absolute" concept and that the LT is easy to measure and determine. I just do a LT test, take the data, and then go put it to use. Nothing can be further from the truth. What criteria are you using to determine the LT? 2mM rise from baseline, 4 mM, breakpoint...??? 10 scientists will give you 10 different answers.
Unless you are one of the Galen Rupps or Eliud Kipchoges of the world, just go run! Too many people are splitting-hairs over whether their LT is 5:16 or 5:21 pace and then discussing this while eating a bowl of chocolate-frosted-sugar-bombs. Until you are doing most EVERYTHING else right, there is no need to be concerned with whether or not the LT is 5:16 or 5:21 pace.