I added another article on the Bronze Age, where how characters were presented changed dramatically, to the wiki.
Our library says the Bronze Age started in 1971. Others put it as early as 1968 and as late as 1973.
Below are the important dates for that time period. Notice that Denny is crucial for many of them.
Denny’s background was as a reporter, sensitive to social issues and trained to meet deadlines. He did not come from fandom. Also he had a wife and baby and thus could not reject any work.
1968 Writers Otto Binder, Bill Finger, John Broome, Arnold Drake, and Gardner Fox asked DC management for more financial benefits, including reprint payments, higher page rates and health insurance. Most were no longer given any more work.
Justice League of America 65
Justice League of America 66
Denny O Neil
Some say these writers leaving DC was the true end of the Silver Age.
1968 Wonder Woman surrendered her powers Denny O’Neil and editor/plotter/artist Mike Sekowsky
1970 Green Lantern Green Arrow 76 O’Neill Adams
1970 Marvel Conan the Barbarian Roy Thomas
1971 Superman 233. First Superman under editor Julius Schwartz By O’Neil, Swan Anderson
1971 Batman 232 “Daughter of the Demon” writer Denny O’ Neil and atist Neal Adams redefined the Batman
1971 New Gods Kirby comes to DC
1971 Marvel Kree–Skrull War Roy Thomas,Sal Buscema, Neal Adams, and John Buscema.
1971 Comic Code Authority standards revised. Code now permited the depiction of “narcotics or drug addiction” if presented “as a vicious habit”.
Also, newly allowed were "vampires, ghouls and werewolves
1971 Marvel Savage Tales 1 First appearance of Man Thing, By Thomas Conway. Later THE Writer of Man Thing was Steve Gerber
1972 Swamp Thing Wein Wrightson
1972 Marvel Tomb of Dracula Wolfman Colan
1973 Marvel The Amazing Spider-Man 121-122 The Night Gwen Stacy Died, by Conway, Kane.