Squaregonial jaw with gonial angle will leads to:
Low mandibular plane angle
Increased mandibular plane angle
No change
Low or increased mandibular plane angle
In the horizontal growth pattern, there is a tendency for the mandible to rotate upward and forward. The lower anterior facial height is relatively short with a tendency for deep bite. 
Such persons have a squarish face, a low mandibular plane angle, well-developed jaw elevators, increased biting force, and broad dental arches.
Ref: Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities THIRD EDITION
Om P. Kharbanda, pdf no 670