The pioneer work on deltaic sedimentation was done by G. K. Gilbert, and published in 1885, and in 1890. The deltas which he so carefully described were built into Pleistocene Lake Bonneville by rivers and creeks entering the lake from the rugged Wasatch Mountains to the east.

The classic concept of the delta, as described by Gilbert, with distinctive topset, foreset, and bottomset beds, was incorporated into virtually all introductory textbooks in geology as a "typical delta". It has persisted until the present time, in spite of the publication of many papers on such complex deltas as the Mississippi and others quite different from Gilbert's classic, simple delta. The term "Gilbert-type Delta" was introduced by Bates in 1953, who characterized it as a product of homopycnal flow into lakes.

The present paper describes and illustrates some typical Lake Bonneville deltas as "Gilbert-types". The deposits are characterized by:

1. Essentially homopycnal flow by mountain streams of steep gradient into deep water immediately offshore.

2. Occasional turbidity flows (mud-rock flows); hyperpycnal.

3. Coarse gravels dominant in foreset beds.

4. Fine sands and silts in bottomset beds, prograded locally to receding lake levels.

Some of the deltas of Lake Bonneville are true counterparts of alluvial fans.

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