On the way to work I came across this stretch of sidewalk, and I stopped in my tracks.

The ghostly stains were the traces of fallen maple leaves.

As I learned later from researching the phenomenon on Google, it sometimes happens, in Fall, when conditions are just right, that a natural dye in a dying leaf leaches out to mark its temporary resting place on a concrete bed.  When winds come and blow away the leaves, what's left behind are tannic acid-generated "leaf prints."  

These possess the spookiness of fossil imprints in shale.

Understanding this natural process brought to mind somber lines from Shakespeare's Sonnet LXXIII.  Consider the sidewalk, cradling the leaf,

As the death-bed, whereon it must expire,

Consumed with that which it was nourish'd by. 

_______________________________________________________________________________

Notes:

1.  Two other bloggers have written about this phenomenon, here and here.  

2.  Shakespeare's Sonnet LXIII (73) is available on the "Shakespeare's Sonnets" website, here.