Heat Shield Rock
Another possibility that occurred to me, for the origin of Heat Shield Rock;
When an impactor strikes Meridiani, it throws rocks all over the surrounding landscape. The rocks native to the area quickly weather away to dust and blueberries. Non native rocks would last longer, and iron-nickel meteors would last a long time.
Perhaps Heat Shield Rock originally created a crater and over time became buried under sediments and sedimentary rocks. Later, another impactor blast the rock, along with native rock, onto the surrounding plane. The native sedimentary rock weathers leaving the meteor.