Indiana Code Title 36. Local Government § 36-7-11.3-16

Sec. 16. (a) A preservation area consists of:

designated by the legislative body.

(b) The primary area is a primarily residential area that the legislative body finds after a public hearing to be a clearly definable area that:

(c) The secondary area is an area surrounding the primary area that the legislative body finds after a public hearing to be an area the control of the development or change of which is necessary or desirable to the preservation of the primary area.  The legislative body may decide to not designate a secondary area if the legislative body determines that a secondary area is not needed or required to preserve the primary area from deterioration or destruction.