Sounds like you have a mechanical gauge. Oil is supplied via that capillary tube directly to the gauge which measures and displays the pressure. Does the gauge drop to zero when the car is off? What does it show at normal operating temp at idle? Normal would be anywhere from 30-60 psi or so depending on how fresh the engine is.

100psi at highway speeds is on the high side, so it is possible that the gauge is not accurate.

If there is ANY oil showing on the dipstick, its got enough to supply the pump fine on level ground, not cornering.

I'd first be leaning at an electrical issue... probably the wire twixt the sending unit on the engine and the light is rubbing something.. the exhaust or the edge of the hole in the firewall through which it goes. Or getting pinched under the the valve cover. Them are the three locations I've seen the most.

Or your engine could be fried. We'll hope that's not the case, but if it is, it's really not a huge deal.
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-Matt I ♥ my ♂