SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

o

Rule 13d-1(b)

x

Rule 13d-1(c)

o

Rule 13d-1(d)

(1)

Names of Reporting Persons
G1 Execution Services, LLC

(2)

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

(3)

SEC Use Only

(4)

Citizenship or Place of Organization
Illinois

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

(5)

Sole Voting Power
0 (1)

(6)

Shared Voting Power
4,122,795 (1)

(7)

Sole Dispositive Power
0 (1)

(8)

Shared Dispositive Power
4,122,795 (1)

(9)

Aggregate Amount Beneficially Owned by Each Reporting Person
4,122,795 (1)

(10)

Check box if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  o

(11)

Percent of Class Represented by Amount in Row (9)
2.6 %

(12)

Type of Reporting Person (See Instructions)
BD, OO

(1)

Names of Reporting Persons
Susquehanna Investment Group

(2)

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

(3)

SEC Use Only

(4)

Citizenship or Place of Organization
Pennsylvania

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

(5)

Sole Voting Power
112,200 (1)

(6)

Shared Voting Power
4,122,795 (1)

(7)

Sole Dispositive Power
112,200 (1)

(8)

Shared Dispositive Power
4,122,795 (1)

(9)

Aggregate Amount Beneficially Owned by Each Reporting Person
4,122,795 (1)

(10)

Check box if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  o

(11)

Percent of Class Represented by Amount in Row (9)
2.6%

(12)

Type of Reporting Person (See Instructions)
BD, PN

(1)

Names of Reporting Persons
Susquehanna Securities

(2)

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

(3)

SEC Use Only

(4)

Citizenship or Place of Organization
Delaware

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

(5)

Sole Voting Power
4,010,595 (1)

(6)

Shared Voting Power
4,122,795 (1)

(7)

Sole Dispositive Power
4,010,595 (1)

(8)

Shared Dispositive Power
4,122,795 (1)

(9)

Aggregate Amount Beneficially Owned by Each Reporting Person
4,122,795 (1)

(10)

Check box if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  o

(11)

Percent of Class Represented by Amount in Row (9)
2.6%

(12)

Type of Reporting Person (See Instructions)
BD, PN

Item 1.

(a)

Name of Issuer
Cliffs Natural Resources, Inc.

(b)

Address of Issuer’s Principal Executive Offices
200 Public Square

Suite 3300

Cleveland, OH 44114-2315

Item 2(a).

Name of Person Filing
This statement is filed by the entities listed below, who are collectively referred to herein as “Reporting Persons,” with respect to the shares of Common Stock, $0.125 par value per share, of the Company (the “Shares”).

(i)  G1 Execution Services, LLC

(ii) Susquehanna Investment Group

(iii) Susquehanna Securities

Item 2(b).

Address of Principal Business Office or, if none, Residence
The address of the principal business office of G1 Execution Services, LLC is:

440 S. LaSalle Street

Suite 3030

Chicago, IL  60605

The address of the principal business office of each of Susquehanna Investment Group and Susquehanna Securities is:

401 E. City Avenue

Suite 220

Bala Cynwyd, PA 19004

Item 2(c).

Citizenship
Citizenship is set forth in Row 4 of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person.

Item 2(d).

Title of Class of Securities
Common Stock, $0.125 par value per share

Item 2(e)

CUSIP Number
18683K101

Item 3.

If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

o

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b)

o

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c)

o

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d)

o

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e)

o

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)

o

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)

o

A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G);

(h)

o

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

o

A non-U.S. institution in accordance with § 240.13d–1(b)(1)(ii)(J);

(k)

o

Group, in accordance with rule 13d–1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with § 240.13d–1(b)(1)(ii)(J), please specify the type of institution:____________________________

Item 4.

Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

The information required by Items 4(a) — (c) is set forth in Rows 5 — 11 of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person. The amount beneficially owned by Susquehanna Investment Group is comprised of options to buy 112,200 shares of the Company’s Common Stock.  The amount beneficially owned by Susquehanna Securities includes options to buy 3,370,900 shares of the Company’s Common Stock.  The Company’s quarterly report, on Form 10-Q, filed with the United States Securities and Exchange Commission on October 29, 2015, indicates that there were 153,422,672 shares of Common Stock outstanding as of October 26, 2015.

Item 5.

Ownership of Five Percent or Less of a Class

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following:   x

Item 6.

Ownership of More than Five Percent on Behalf of Another Person

Not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person

Not applicable.

Item 8.

Identification and Classification of Members of the Group

Not applicable.

Item 9.

Notice of Dissolution of Group

Not applicable.

Item 10.

Certification

By signing below each of the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

G1 EXECUTION SERVICES, LLC

SUSQUEHANNA INVESTMENT GROUP

By:

/s/ Brian Sopinsky

By:

/s/ Brian Sopinsky

Name:

Brian Sopinsky

Name:

Brian Sopinsky

Title:

Secretary

Title:

General Counsel

SUSQUEHANNA SECURITIES

By:

/s/ Brian Sopinsky

Name:

Brian Sopinsky

Title:

Secretary

EXHIBIT

DESCRIPTION

I

Joint Filing Agreement*