NORMAN, Okla.--Nicole Rivera and Melissa Chmielewski each hit solo home runs as North Dakota State completed a surprising sweep through NCAA softball regional play with a 4-1 win Sunday against Tulsa.

NDSU now moves on to the 16-team Super Regional level, where they will meet defending national champion Arizona State University (44-17), which defeated Louisiana State University 5-0 Sunday night, in a three-game series.

Should NDSU win that series next weekend, the team would move on to the eight-team Women's College World Series in Oklahoma City.

Andi Padilla (26-10) threw a two-hitter for the fourth-seeded Bison and didn't allow a hit after the third inning. Padilla pitched all 25 innings for NDSU and recorded a 0.84 earned run average. She allowed 11 hits and only three runs with 11 walks and 11 strikeouts.

Rivera led off the game with her first home run of the season before Tulsa (40-17) answered in the bottom of the first on Kailey Yarmer's sacrifice fly. It was Rivera's second career home run. Rivera hit .462 during the three-game set and has hit over .380 over the past 26 games.

North Dakota State (38-18) went back ahead with two runs in the third, including Chmielewski's home run to left to left off starter Jackie Lawrence (21-6). It was Chmielewski's team-leading 10th home run of the season. She also hit .462 during the three-game regional.

Taylor Lynn added an RBI single in the sixth inning to extend the Bison lead to 4-1.  

Padilla took advantage of a stingy North Dakota State defense, particularly from second baseman Laurel Pipkin. Pipkin made one diving stop and throw to Chmielewski to record the third out in the fourth inning.

In the fifth inning, Pipkin fully extended to stop a ball targeted for center field, scrambled to her feet and recorded the first out of the frame with a runner on first. That type of effort typified the Bison overall defense during the regional with no errors in 99 fielding chances. NDSU ranks 11th nationally in fielding (.975).

North Dakota State reached the NCAA tournament in its first year of eligibility after moving up from Division II. The Bison are the first Summit League team to advance past the NCAA Softball Regionals since DePaul reached the College World Series in 1999.