Question
Trees are on each side of a gravel driveway.  Fresh gravel was put on the driveway and filled also around the two trees, I am guessing maybe around 4-5" of new gravel.
We noticed a couple of weeks later the leaves on the oak trees were curling up turning brown.
We dug out the gravel fill around the tree bark. thinking this was the reason for the dying leaves.
Now what should be do to treat these two trees to get them back to normal.  

Answer
Fill dirt is frequently added around existing mature trees so that a level or more visually desirable lawn can be established. Fill dirt changes the ratio of oxygen to carbon dioxide around tree roots and the roots may die. Only a couple of inches of soil will cause damage but 4-5 inches of gravel will kill most of the root system. The roots extend out about 1  1/2 times the spread of the foliage and any fill over this area will kill roots. I would move any of the fill you can from around the tree--the gravel on the drive side may not be able to be moved. I would then water the tree with 1 inch of water every third day-place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop. At the very least you can expect some dieback of limbs. But the deep watering may help the roots.