Sunday I was flying for about 35 minutes when I heard a loud "thunk". At first I thought I had hit a large bird, but the deaffening silence told me I had no power. I had just checked guages a minute or so before, oil temp and pressure good. I was 1200 ft AGL cruising about 4000 rpm 4 miles west of my home airprort CZL thinking about turning in for a 45 to downwind on runway 35. Out the left side was a large ag field so I went throught my emergency procedures shutting everything down (don't remember doing half of it!) made a normal downwind, base and final. I did some agressive slipping to get down to the field but wasn't necessary in the end. Normal smooth landing and rolled out about 250 feet. At that point I crossed a shallow depression and it turned me left and rolled another 20 feet. Absolutly no damage to the pilot or aircraft. Upon getting out of the AC, found no oil underneath. The prop now free wheels. After about fifteen minutes oil started dripping out. Upon removing top cowling oil was coming from a broken fitting at the block. The fitting was still attached but oil coming out around the fitting. Don't know if it broke when the engine stopped immediately. I did have both cowls off two weeks again and check all fittings and wires, etc and this was my next flight. The engine is locked up. Someone speculated something broke in the gear box. It is a 912ULS with no cluth. Engine has 76 hours on it. By the time I got it back to the hanger it was too dark to see much so next weekend I'll go do further investigation.