It is possible to build a pond 14' deep when you have bedrock at 8',
IF you have enough elevation change to the springs that are your source of water.

What is the elevation of your springs relative to the elevation of the bedrock at the location of your proposed pond?

If the spring is greater than 14' higher, you can still accomplish your pond design goal. You need to either build a spring box to capture the water at each spring and then pipe it into your pond, or drive a horizontal sand point line back into the spring for the same purpose. (It depends upon your local geology.)

If that is achievable, then you need to dig down to the bedrock for essentially all of the projected pond bottom. Clear any boulders (you can use them for landscaping). If the base is solid bedrock, then you might get by with a 1' thick clay seal at the base of your pond. If the rock is fractured or has fissures, then you probably need a clay seal of at least 2' to seal a water depth of 14'.

You then need to move all of your excavation spoils to build a berm around the pond. Save the best clay to seal the sides of your pond as you finalize construction.

This WILL NOT be a beautiful pond that follows the lay of your land. If you have 14' of water depth at the deepest point, then the top of the berm will be 8' above the surrounding land (2' of clay + 14' of water - 8' excavated to bedrock). If you are standing on flat ground outside of the construction zone, then you will see a berm or dike to a point above your eye level.

I think that could still be very scenic if your cabin is 40' above the pond! Also, if you enjoy landscaping, then a sloped berm is an excellent blank canvas for your designs!

If you have good clay on site to seal the bottom and sides of your pond, plus a sufficient elevation differential between the springs and the pond, you can still get what you want.

If you do not have exactly all of the right features in place, then you need to decide what trade-offs you must make to achieve the pond that is closest to your dream pond, but is still technically and financially achievable. (PLUS can be permitted as others have pointed out.)

Good luck on your new pond project!