The American painter Mary Lovelace O’Neal, who was active in the Civil Rights movement of the 1960s before eventually winning acclaim for abstract works that defy categorization, died in Mérida, Mexico, on Sunday. She was 84. Her death was confirmed by her galleries, Jenkins Johnson and Marianne Boesky, on Wednesday.

In a career spanning more than 50 years, Lovelace O’Neal produced energetic, large-scale paintings whose subjects are blurred among layers of rolled and dripped paint. As a young artist living in New York in the 1960s, she forged a practice that was critiqued by both the Black Arts Movement and the city’s avant-garde.…