Science Questions/ aka Could the following be possible?

[The Rock Worm]

As it is Thanksgiving Day, I'm on a bit of a pause from my Dark Depths story. Trying to open doors in an area full of water just doesn't work, which made me re-think my puzzle/story for the better. As you know I love stories that have enough fact that it could be possible. That said, I do have a question about if the following is possible.

For those how haven't read Steve Alten's MEG: Hell's Aquarium, let me describe one aspect that is a central plot in the story. Better yet, let me put this excerpt from the book talking about it:

“The first clues that led Dr. Maren to discover the true nature of what lies beneath the Philippine Sea began
with a comprehensive study of the Shikoku and Parece Vela Basins back in 1979. Two geologists, Drs.
Mrozowski and Hayes, found irregular oceanic crust and magnetic anomalies along these eastern basins. More
recently, researchers at the University of Sydney reported anomalies in the basement sediment of the Parece
Vela Basin.”
“What sort of anomalies?” Jonas asks.
“Geological age discrepancies. Big ones. While the northern section of the east basin, the Shikoku, is less
than 30 million years old, the basalts dredged from the Parece Vela Basin reveal geochemical characteristics
that date back to the Early Cretaceous period, approximately 150 million years ago. We now believe the floor of
the Parece Vela is actually part of an ancient sea shelf that formed as far back as 275 million years when two
continental plates rifted apart, the magma creating a crust that eventually stretched east before colliding with the
Western Mariana Ridge, approximately 7,000 feet below the surface. This remains a working theory, mind you,
but it is supported by Dr. Maren’s overwhelming evidence. More important is what Maren discovered hidden
beneath the basin . . . a vast ancient sea that has remained isolated from the Pacific for hundreds of millions of
years!”

So, I have two questions concerning this concept.

Question 1: Are there Geological Age Anomalies in the Parece Vela Basin? I did find this link http://sciencelinks.jp/j-east/article/20...760625.php that indicates an anomaly in Topography in this area.

Question 2: Could a hidden sea realistically be beneath a basin 'floor'?

The ocean is still largely unexplored, so the possibility of new life being discovered is a fact, but a hidden sea beneath the basin intrigues me. Just curious if this concept is possible or not. Happy Thanksgiving everyone!!!