geosciencebigpicture

Who knows from what depths the well of ideas flows? For me it is often during the liberation of rote manual work that frees some bandwidth while still requiring a minimal level of focus and blood flow to the brain. Yet another aspect to what I call Manual Prayer.

Anyway, I’ve been puzzling over some very strange features in the arcane world of seafloor isochrons. These have been addressed in posts Charybdis and the Oldest Ocean Floor on Earth and Great Mysteries of Nature Nobody Seems to be Thinking About.

I call that circular feature in the Ionian Sea Charybdis. The isochrons increase in age towards the center in an omega pattern along a transform fault until the very center where there is a completely circular 270 million year old isochron.

We have this very nice notion of plate tectonics where magma emerges at linear spreading centers and spreads outward in both directions leaving us stripes of magnet alignment as the poles have reversed through time. These stripes march dutifully across the ocean basins where the oldest descend into trenches at continental margins or island arcs to be recycled into the mantle.

How then do we account for closed geometric features whose stripes become older toward the center? It is tempting to think of some sort of fragmentary spreading center or hot spot emerging and spreading out, but nothing we see today seems to behave that way with the possible exception of the Ring Around Antarctica on an enormous scale. We see evidence of hotspots and seamounts all over the ocean basins, including Hawaii, but none of them shows any tendency to spread out into a closed pattern.

So what about impacts? Charybdis sure looks like one all right, but why would circular magnetic stripes and isochrons emerge? Well, the wild idea is that it is not really surprising. Magma emerges at weaknesses and any hole punched in the oceanic crust will be a weakness. Magma might solidify first in the center and spread out to effectively “patch” the hole.

The center of Charybdis is the oldest ocean floor on earth we know of and it has a friend of similar age over by Lebanon. If these are impact signatures, the isochrons date them before the Permian Extinction.

Note how both features are adjacent to important transform fault systems. Let’s head for Club Med and an impact we are pretty sure of.

The purple isochrons north of the impact are a hundred million years older than the impact wat done in de dinos, but they constrain the damage and show some deformation. Note the relationship to the transform system. It is also not surprising that an impact might cause a crack, but the seafloor “patch” in the crack, including the circular feature follows the normal pattern, opposite of Charybdis and the Pacific Triangle, with the youngest very recent ocean floor in the center and older floor approaching the age of the impact left and right.

And then the Pacific Triangle.

Now THATS a patch! The center of the triangle would place the impact at about 175 million years ago, a time in the Jurassic so unremarkable that it is difficult to even find a continental reconstruction for the period. The dinosaurs seemingly could not have cared less and thrived in great weather for the next 110 million years. It was generally the time that Pangaea began breaking up and there was a bit of glaciation…

Just goes to show how little we really know. Back to prayer and future wild ideas.