Sindarius Thornwell scored 17 points and the 13th-seeded Gamecocks charged into the SEC tournament quarterfinals with an upset of the No. 5 seed Razorbacks in Atlanta. Laimonas Chatkevicius had 16 points and seven rebounds off the bench for South Carolina (14-19), which previously knocked off Auburn in the first round and will next meet No. 4 seed Tennessee on Friday. Duane Notice scored 11 points and Mindaugas Kacinas grabbed 10 rebounds as the Gamecocks won their second straight tourney game after a six-game skid in the annual event. Coty Clarke led four players in double figures with 13 points for Arkansas (21-11), which was dealt a mammoth blow in its bid to earn an NCAA tournament at-large selection. Bobby Portis and Rashad Madden had 11 points apiece and Michael Qualls tallied 10 as the Razorbacks suffered their seventh straight tournament setback. Anthlon Bell buried a 3-pointer at the buzzer before halftime to get Arkansas within 35-32 and the Razorbacks went ahead a little over two minutes into the second half, which saw several lead changes from that point on. Clarke drained a 3-pointer with three minutes left to put Arkansas up 67-66 and Qualls scored on the next possession to make it a three-point bulge. However, the Razorbacks would not score again - missing their final four shots - and South Carolina was able to pull ahead at the line, despite making just 5-of-10 in the final two minutes. After Michael Carrera split a pair with three seconds left to cap the scoring, Madden's shot from just inside half court clanged off the rim. GAME NOTEBOOK: South Carolina had a 40-24 rebounding advantage. ... The Gamecocks had made 25-of-31 free throws before their late swoon at the line. ... Arkansas C Moses Kingsley had seven points and four of his team's six blocked shots off the bench.