Secret Tombs:
By solving the puzzle at each tomb you will get a treasure map.
If you complete all of them you get the "Intellectually Superior" achievement.

Tomb Of The Unworthy
Coordinates: 53N 712478, UTM 3416188
Reward: Mountain Village Relic Map
Once you have the Climbing Axe, travel to the Mountain Village and return to the Tomb of the Unworthy at the base of the waterfall.

Light the torch when you enter the tomb with either the pot or some flint. Burn the bodies on the mesh platform and push of the extra weight. Wait for the lift to rise and then climb to the treasure chest at the top. 

Halls Of Ascension Tomb
Coordinates: 53N 712501, UTM 3416206
Reward: Mountain Village GPS Cache Map
Once you have the Flint and Rope Arrows, travel to the Overlook camp in the Mountain village, where you looked for the rescue plane's smoke signal. Use the rope arrow to reach the upper route on the north ledge then use it again to reach the tomb.

There is an open window on the left and a suspended platform in the center. Use the crank to close the shutters on the left and then turn the center crank to raise the platform. When the second shutter opens a strong gust of wind will move the platform; get on the platform before it does. Jump to the wooden board and hang on to the ledge. Move along the ledges to reach the treasure chest. 

Well Of Tears
Coordinates: 53N 712580, UTM 3416067
Reward: Shantytown Relic Map
Once you have the Rope Arrows, travel to the Helicopter Hill camp in Shantytown.
In the town there is a building painted with white murals and armed with traps. Go through the floor and you will drop down on the path to the tomb.

Throw all the yellow canisters inside the tomb onto the hanging platform above. When it's down, stand on it and remove the canisters. Get off the platform and then use the upper ledge to jump to the raising platform. Quickly jump to the left ledge to reach the treasure chest. 

Chamber Of Judgement
Coordinates: 53N 712616, UTM 3416053
Reward: Shantytown GPS Cache Map
Once you have the Climbing Axe and Rope Arrows, travel to the Windmill camp in Shantytown.
Go to the southern part of town and find the caves to the east, below the gondola station. Slide down the surface to reach the ledges. Once you've climbed the ledges, follow the right passage and it leads to the tomb.

Throw all the yellow canisters inside the tomb onto the raised part of the seesaw. Jump to one, then use a rope arrow on the other. Jump to the rock wall by using the seesaw then climb to reach a ladder. The ladder leads up to the treasure chest. 

Stormguard Sanctum
Coordinates: 53N 712635, UTM 3416007
Reward: Summit Forest Relic Map
Once you have the Fire Arrows, travel to the Hunting Lodge camp in the Summit Forest.
Go north beyond the bridge and you will find the tomb entrance with a lamppost next to it.

Explode the gas with a fire arrow, cross it, then use another arrow to blow up the crates on the ledge. Climb up the rock wall to reach the treasure chest. 

Temple Of The Handmaidens
Coordinates: 53N 712485, UTM 3415986
Reward: Shipwreck Beach GPS Cache Map
Once you have the Rope Ascender and Climbing Axe, travel to the Survivor's camp at Shipwreck Beach.
Go the the zipline to the north and you'll reach a barricade. Use the rope ascender to break the barricade, then continue through the cave to reach the tomb.

Use the crank to raise a platform and release the buoy. Follow the buoy as it moves by climbing the left ledge. When the bouy releases a turning pole, use the pole to jump the gap and then use a rope arrow on the white beam below. Wait for the buoy to continue and then push the beam. Once it lines up, jump to the bar to reach the rock wall that leads to the treasure chest. 

The Flooded Vault
Coordinates: 53N 712521, UTM 3415962
Reward: Shipwreck Beach Relic Map
Once you have the Climbing Axe and Prying Axe, travel to the Cliffside Bunker at Shipwreck Beach.
The tomb entrance is in a narrow passage near the top of the climbing path that leads to the bunker. Press the button up the stairs first and then press the button beside the door to enter the tomb.

Inside you will see electricity in the water and a floating platform. Release the platform by lighting the anchor rope, then shoot the wooden barrier on the right with a gun. Shoot a rope arrow through the barrier and pull the platform towards the steps, then use another rope arrow to pull on the beam at the far end of the room to raise the generator. Moving the plaform underneath the generator will make the water safe so you can cross it and reach the treasure chest. 

Treasure map locations:
Search the 14 locations to find all the treasure maps, which reveal the locations of all relics, GPS caches and documents on your map. Buying the Tier III Survival skill "Cartography" will reveal all treasure map locations on your map. 

Costal Forest
Coordinates: 53N 712382, UTM 3416112 
1: On the eastern area of the map there is a broken bridge near a waterfall. To reach the waterfall, find the rock ledge with a wooden plank. Jump from there to the beam on the bridge and the treasure map will be on the crate at the next platform. 

Mountain Temple
Coordinates: 53N 712430, UTM 3416148 
2: After climbing the ladder you will face a large decayed building. Take the left path to reach the waterfall and then dive down into the water to find a secret cave, with the treasure map inside on top of a crate. 

Base Exterior
Coordinates: 53N 712390, UTM 3416289 
3: At the Radio Tower camp, use the zipline to the east to reach the building below. You will land near a burning trashcan; the treasure map is right behind it. 

Mountain Village 
4: Complete the Tomb of the Unworthy to unlock the corresponding treasure map. 
5: Complete the Halls of Ascension to unlock the corresponding treasure map. 

Shantytown 
6: Complete the Well of Tears to unlock the corresponding treasure map. 
7: Complete the Chamber of Judgement to unlock the corresponding treasure map. 

Shipwreck Beach 
8: Complete the Temple Of The Handmaiden to unlock the corresponding treasure map. 
9: Complete The Flooded Vault to unlock the corresponding treasure map. 

Geothermal Caverns
Coordinates: 53N 712708, UTM 3416013 
10: At the location is a tall wooden scaffolding, climb it to find the treasure map at the top. 

Cliffside Bunker
Coordinates: 53N 712561, UTM 3415929 
11: Use the rope ascender on the wall behind the big cannon to destroy the wall. The treasure map is inside on top of some sand bags. 

Summit Forest 
12: Complete the Stormguard Sanctum to unlock the corresponding treasure map. 

Research Base
Coordinates: 53N 712433, UTM 3416048 
13: On the top left corner of a big pile of boxes is a small opening big enough to crawl through. The treasure map is right behind the boxes. 

Chasm Shrine
Coordinates: 53N 712594, UTM 3416259 
14: The map is on the second floor, jump up and you can find it lying on a table. 

"Chatterbox" Achievement Hint:
There are seven moments during the story when you can talk to your friends. If you listen to everything they have to say you unlock the "Chatterbox" achievement, miss one word and you can't get it on that playthrough. 

1: Before you search for 50 pieces of salvage, talk to Whitman. 
2: After you've found 50 pieces of salvage, talk to Whitman again. 
3: After helping Roth against the wolves, talk to Roth. 
4: When you receive the rope arrows, talk to Roth before using the zipline. 
5: Upon reaching Shipwreck Beach, talk to your friends Sam, Reyes and Jonah. 
6: Before going to the Endurance to help Alex, talk to Whitman, Sam, Jonah and Reyes at the beach camp. 
7: After you've gone to the Endurance, talk to Whitman, Reyes and Jonah.