JMO, the oil got over heated and lost all viscosity and is burnt..
I would do an oil change , cost about $17.00 and see how it sounds then.
Is this a hydraulic lifer /6 ? and was it not knocking before this happened ?
Do you have an oil pressure gage or light ?
If you want/have to open it up and look at your bearings I would go threw it while it is out and have a new /6 in your car.. JMO..
But I would definitely do an oil change and see what it sounds like then.
