Sheet intrusion
（重定向自Intrusive sheet）
![A sill of monzonite intrudes Cambrian carbonate bedrock, near Notch Peak, Utah.](/Images/godic/202501/20/NotchPeakDike2147.JPG")
A sheet intrusion, or tabular intrusion, is a planar sheet of roughly the same thickness, that forms inside a pre-existing rock. When it cuts into another unlayered mass, or across layers, it is called a "dike". When it is formed between layers in a layered rock mass, it is called a "sill".