The phrase "extensive section" is correct and usable in written English.
You can use it to describe a large or lengthy portion of something, such as a book or article. For example, "The book contains an extensive section on the history of the region."
There's also an extensive section on religion, with particular emphasis on Sikhism.
The EverythingUSB site has an extensive section devoted to U.S.B. 2.0 products and frequently asked questions at www.everythingusb.com/usb2.
A more extensive section (~583 m2) was reconstructed in the shallower part (1,325 1,305 m) the Coral Wall.
The marketing guide is an invaluable resource for all things livestock and has an extensive section on slaughter and marketing regulations.
On the official Eton website, an elegant sales brochure with pictures of sunlit old school walls and pupils in their ancient, photogenic uniforms, there is an extensive section on "famous Old Etonians".
This wall any of you who've come to Rome by train, and the Stazione Termini, see a very extensive section of the Servian Walls, as you get out–I don't know if you've noticed it, but you should see an extensive section of the Servian Walls right outside the train station.
Ms. MacDonald also recommended deleting extensive sections on the loss of sagebrush habitats to agriculture.
Germany is the only remaining large country where motorists can drive at any speed on extensive sections of rural motorway.
With these reconstructions, it was possible to interact with extensive sections of video footage and precisely position individuals.
Other thick loess deposits are found in Europe and Asia, including extensive sections along the Huang He (Yellow River) west of Beijing.
tomshardware.com -- This Tom fellow knows a thing or two about computers, and his site has extensive sections on motherboards, RAM, monitors and video cards.
