With its gigantic budget, B-tier cast and faint yet unshakable aura of cruddiness, “Sahara” suggests a throwback to the heyday of ’70s megaproducer Dino De Laurentis (“Barbarella,” “King Kong”).

Sure, the movie takes place in present-day Africa, but at any given moment, it feels like Jane Fonda might jiggle across the screen in plastic knee-highs, wielding some sort of laser weapon. Instead, “Sahara” invents a hero almost as silly: Dirk Pitt, the death-defying fortune hunter first conceived in the adventure novels of Clive Cussler.

Played by Matthew McConaughey (“U-571”) in the year's most ab-clenching performance, Pitt is essentially James Bond for the redneck set. A former Navy man equally versed in microbiology and muscle cars, Pitt is tough enough to duke it out with killers in turbans but vain enough to stick the occasional tulip in his lapel. Typically, you will find him straddling valuable pieces of foreign archaeology, flashing his blinding white grin to the tune of Grand Funk Railroad's “We're an American Band.”

“Sahara” — adapted by four different screenwriters from Cussler's best-selling novel — finds Pitt in western Africa, cruising the Niger River with his wiseacre sidekick/lifelong pal, Al Giordino (Steve Zahn from “Happy, Texas”), looking for a lost Confederate ironclad warship that somehow crossed the Atlantic in the waning days of the Civil War. Along the way, the boys hook up with Eva Rojas (Penelope Cruz from “Blow”), a fiery do-gooder with the World Health Organization who has traced a mysterious disease to the landlocked African nation of Mali. Helpful hunk that he is, Pitt gives the good doctor a ride on his speedboat.

Quickly, the expedition runs afoul of a vicious Mali strongman (Lennie James) who'll stop at nothing to conceal the evils of his government, variously involving toxic waste, odious French industrialists and repressed Tuareg tribesmen. Mali, which in fact has been democratic since 1991, gets dissed royally by first-time director Breck Eisner and his quartet of scribes, but then, the Mali lobby in Hollywood isn't what it used to be.

Eisner, the son of outgoing Disney CEO Michael Eisner, appears to have cashed in his nepotism chips just in time. Though the action sequences in “Sahara” are visually impressive (that $130 million had to go somewhere), the storytelling ingenuity is not — Pitt's solution for getting out of any given jam is simply to blow up the nearest vehicle or chunk of Third World mountainside. It's a deep-fried demolition fantasy for adolescent boys, down to the stern-but-loving father figure — Admiral James Sandecker (William H. Macy), Pitt's former superior officer and current boss in a private salvage enterprise — who lends the kids his flashy conveyances and gets comically flustered when Pitt makes them go boom.

“Sahara” is piffle, but it's handsome, fast-paced piffle, and with the movie's fizzy mixture of comedy and adventure, it would be fair to call it this season's answer to “The Mummy” — couched praise if there ever was.

And isn't there a certain amusing topicality in Pitt, an affable Texan who traipses around the globe, smiting bad guys and protecting our planet's precious ecology? Even as we watch him hop moving trains and pummel villains on helicopter pads, we know this American warrior is nothing more than a mirage.