Are we as landowners at the mercy of the "Oil Companies" determining what formations are present or under our land? We only find out when they are hyping the "Company"
As to your first question, the answer is "yes" if you mean "in general", or "yes" if you mean where in the sedimentary column you would find it. But "no" still applies as to exact dimensions and full extent, and certainly "no" applies to the productive extent of the HS.
The Austin Chalk is a totally different strata. It is found above the Tuscaloosa (Woodbine) sand, which in NW LA is pretty shallow. Same answers above apply to this zone as well,except that the Austin Chalk was targeted fairly extensively during a ten-year period beginning in the early 1990s, with peak drilling occurring between '95 and '98.
When compared to the anticipated productive area of the HS, the productive area in the Austin Chalk play is located in a band across western and central Louisiana (you could more or less draw a crescent-shaped arc across the central part of the state right around the "neck" of Louisiana) which lies south of the current HS fairway.
Geologically, you are looking at strata lying thousands of feet apart in terms of depth, and millions of years apart in deposition. Any further discussion I would cede to a geologist.