Occidental-Shamrock Deal Off

Merger talks between Occidental Petroleum Corp. and Diamond Shamrock Corp. were terminated today, just hours after managements of the two big oil companies announced they had reached tentative agreement on a tax-free stock-swap deal valued at about $3 billion.

Boards of both companies met through the morning to consider the merger. It was not immediately clear which of the boards rejected the plan. “They have agreed to terminate the agreement in principle to merge,” Occidental spokesman Frank Ashley said in a terse statement.