what type of material used for upper oil pan gasket

Hello, That could be the oil pan gasket, but if it leaks while it is parked, it really sounds like a rear main seal instead of the oil pan gasket. The oil pan gasket would need a large leak to drip onto the ground while parked and turned off, because the only oil that can come out of it is oil draining down the insides of the engine crank-case. The rear main seal can leak when the vehicle is off because there is oil draining out of the crankshaft, and onto the ground. If the pan gasket needs to be changed, the oil pan gasket is rubber and can be found at many parts stores. If the original gasket is silicone, use silicone. If the leak is coming from where the engine meets the transmission, probably rear main.