building a south facing wall

I am sure I will need to post this in the construction area as well, but I need to build a new/improved fence around my garden - the deer and elk have ravaged it. It is steep and has four vegetable garden terraces excavated out (not retaining walls, just cut into the hillside.) Based on various local recommendations, I'm thinking of harvesting douglas fir poles around the property for the fence posts - to have a minimum 9 ft fence height. (the fence circumference will end up about 640 ft.)

Along the north fenceline though, which is conveniently the uphill side of the beautifully southfacing slope, I might need to actually figure out how to make the fence 12ft high - to account for the slope (the deer can jump straight and probably clear a 6 ft fence.) Given all that I've read about the ability to grow certain fruits against warm southfacing walls, I am considering buiding possibly a 30-40 ft section of that as wall, instead of fence. The property is within 5 miles of the Pacific Ocean (though nearly 1800 ft elevation) and it is in the banana belt of Oregon, which means I've seen citrus growing in protected locations in yards along the coast. I would love to be able to build a south-facing wall and try some citrus. (I have olives up in the orchard area - and have since learned that deer and elk LOVE young olive trees; those will probably not recover well and will need to be replaced. The animals have left the figs alone though; and I came across a 30ft fig tree in a neighbor's cow pasture a few weeks ago!)

So - any experience building a purpose built garden wall? I was thinking of using earthbag construction to build the wall to keep costs down. Will it absorb and retain the heat well? I'm sure building a 12ft wall will pose construction problems, but am looking for experience from the production/garden side of things before committing to a wall. Other suggested construction that I should consider? Cost and effort are considerations; but I want to install something that works and will be there for the long haul.

Thanks!

You mention poles, do you also have logs? Because the classic log palisade used by frontier forts sounds like it would be suitable. 15-foot logs on end in a 3' trench, spiked together at the top. If you've got a way to mechanize the digging it could even be fairly fast and easy.