U.S. Commodity Funds, best known for its $2.2 billion U.S. Oil Fund (NYSEArca: USO) and $3.8 billion U.S. Natural Gas Fund (NYSEArca: UNG), has filed paperwork with the SEC to launch a new diversified commodities index ETF, based on an index created by SummerHaven Index Management.

The fund will track the newly launched SummerHaven Dynamic Commodity Index (SDCI), an actively managed commodities futures index that has positions in energy, precious and industrial metals, and agricultural commodities, including livestock, grains and softs. It is the firm's first index.

Each month, SDCI picks 14 commodities from a pool of 27 based on fundamental indicators, weighting the selected commodities equally in the portfolio. The index is rebalanced monthly, which, as the company states, makes the SDCI the first "long-only active benchmark for commodity investors."

Regarding the decision to launch an actively managed index, SummerHaven co-founder and Yale University professor K. Geert Rouwenhorst said, "Over the past decade commodities have gained acceptance by investors as an important element of the investment universe. As the asset class has matured, investor interest has naturally shifted towards active management."

Rouwenhorst is best known for his 2004 paper with Gary Gorton, "Facts and Fantasies about Commodity Futures," which kicked off the surge of commodity investing seen in the past five years. (Gorton acts as a senior adviser to SummerHaven.)

In the paper, Gorton and Rouwenhorst showed that an investment in a diversified commodity index over a 50 year period would have seen positive returns that were also negatively correlated to stocks and bonds.

If approved, the fund will be the first nonenergy ETF for U.S. Commodities Funds, which offers futures-based products in natural gas, oil, gasoline and heating oil. As of Nov. 30, 2009, the firm had $6.45 billion in assets under management.

The fund's expense ratio has not yet been announced.

Read more in the prospectus here.