AFAIK, Ethernet has no support for fragmentation; I've never seen, in the Ethernet standards I've read (though I might have missed it), a field saying "this is a fragment of a larger frame". There's fragmentation in the IP layer, but it needs: (a) that the frame contains an IP packet; (b) that the IP packet can be fragmented (no "don't fragment" on IPv4, or a special header on IPv6); (c) that the sending host knows the receiving host's MTU; (d) that it's not a broadcast or multicast packet (which have no singular "receiving host").
You can have working fragmentation if you have two separate Ethernet segments, one for 1500 and the other for 9000, connected by an IP router; the cost (assuming no broken firewalls blocking the necessary ICMP packets, which sadly is still too common) is that the initial transmission will be resent since most modern IP stacks set the "don't fragment" bit (or don't include the extra header for IPv6 fragmentation).
You can have working fragmentation if you have two separate Ethernet segments, one for 1500 and the other for 9000, connected by an IP router; the cost (assuming no broken firewalls blocking the necessary ICMP packets, which sadly is still too common) is that the initial transmission will be resent since most modern IP stacks set the "don't fragment" bit (or don't include the extra header for IPv6 fragmentation).