Asphalt Lakes - (Mini-biome)

Asphalt Lakes would be a mini biome inside Savanna. They would have as the name suggests Asphalt Lakes of varying sizes. Thats not all tho:
The ground around them would be dry and cracked. There would be bones scattered around as well as inside the lakes. There would at random, spawn items that you could get from mobs in savanna, inside the Asphalt.
(You may be able to find fossils here, they would be a really good decoration if collected. Just an idea)

After being broken those bones would give you just a regular bone(with small chance of getting decorative one). Getting Liquid Asphalt
would allow you to craft asphalt cement after you combine it with gravel and(the half-cement) put in furnance.

The liquid asphalt would work like that:
As long as you move the asphalt would seems to be solid. If you stop tho, you will start sinking, the more you sink, the harder and longer it is to get out, if you are inside 50% of your body(or maybe even below it) its impossible to get out withouth external help. You will soon start suffecating(if you go there from side the same applies, asphalt will slowly push you inside) . The rest is basically like normal water but slower.
Larger lakes would spawn drowned. They would behave like it was just a regular ocean.

NOTE: external help includes tnt, creepers or any explosives.

EDIT: If as some other post(s) suggest you would add Hyenas they could mostly spawn around or in this mini-biome