Fjordur has many caves and areas with Aberration creatures and resources. Below are a few of the best ones. The video shows these areas and how to get to them in detail.
Aberration Cave 56.8 84.7
What I call the Aberration cave you will find a lot of good things there from element shards to nameless venom, as well as many tameable Aberration shoulder pets. The terminal for the megapithecus is also there.
Moria/Dvergheim 86.2 5.2 other entrance 83.3 21.2
This is one of the coolest looking places on the map. Follow the path in the cave and you will come to bridge with one of the Aberration areas below. There is a hidden path that will take you to a more resource-rich area. It is a little difficult to find, but go to 2:31 of the video and it will become clear.
Space Cave Parking - 85.0 96.9, Cave 86.3 98.0
The Space Cave is really cool to visit, but it really doesn't have much there that you can't find at other aberration areas. However, this is the only place I have seen bulbdogs.
Green Gems 71.4 1.4
The only place to find green gems. It has an undewater entrance, but it is a terrestrial cave. I recommend that you bring a desmodus, because of the vertical nature of the cave.
Rock Drakes (Asgard Realm) 41.9 49.3
This is the entrance to the Rock Drake cave, and the only cave to have radiation. Outside the cave you can collect mushrooms.