How is relative dating used

It does seem like it's impossible to know unless you have additional information. My feeling that this is some kind of metamorphosed contact zone (or aureole), which transforms sedimentary rocks into their low pressure and high temperature metamorphic equivalents (shales to hornfels, limestone to marble, sandstone to quartzite, etc).It's hard to see, but I think I can see (when zooming in ) some of the white halo extending into the bottom of layer A.That would mean A was present when E intruded, because you can't metamorphose something that's not there.Otherwise, the metamorphic aureole would be cut by layer A.The problem is illustrated in the following picture: My question is about the intrusion (E).Obviously the intrusion must have occurred later than the deposits of layers B, C and D, but how can I tell if the intrusion occurred before or after the deposit of layer A?

The changes in this content help determine the relative age of these fossils.

Radiometric dating: This technique solely depends on the traces of radioactive isotopes found in fossils.

The rate of decay of these elements helps determine their age, and in turn the age of the rocks.

Cross dating: This method compares the age of remains or fossils found in a layer with the ones found in other layers.

The comparison helps establish the relative age of these remains.

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