01345nas a2200157 4500008004100000022001300041245016800054210006900222300001400291490000700305520073700312100002301049700002101072700001601093856007801109 2019 eng d a1547139X00aNORTH AMERICAN COMMISSION ON STRATIGRAPHIC NOMENCLATURE Report 13 -- Revision of Articles 25-27 of the North American Stratigraphic Code to Allow Formal Submembers0 aNORTH AMERICAN COMMISSION ON STRATIGRAPHIC NOMENCLATURE Report 1 a279 - 2810 v163 a

At the 74th Annual Meeting of the North American Commission on Stratigraphic Nomenclature, 23 September, 2019, in Phoenix, Arizona, the Commission voted unanimously to accept the revision of Articles 25-27 of the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 2005), and concomitant changes to Table 2 and remarks in Articles 22, 23, and 30 printed below; specific revisions of the Code are indicated in red color. These replace all older versions of the specified Articles. An application for this revision (Brett et al. 2018) was published in Stratigraphy more than one year prior to the meeting; thus, the vote on this application for revision follows Article 21 of the Code.

1 aBrett, Carlton, E.1 aPratt, Brian, R.1 aLanding, E. uhttp://www.micropress.org/microaccess/stratigraphy/issue-355/article-216002294nas a2200157 4500008004100000022001300041245022000054210006900274300001400343490000700357520165700364100002302021700002102044700001602065856005502081 2018 eng d a1547139X00aNORTH AMERICAN COMMISSION ON STRATIGRAPHIC NOMENCLATURE Note 68 - Application for Addition of Submembers to the North American Stratigraphic Code: A Case for Formalizing Lithostratigraphic units of Intermediate Rank0 aNORTH AMERICAN COMMISSION ON STRATIGRAPHIC NOMENCLATURE Note 68  a103 - 1080 v153 a

The existing hierarchy of formal lithostratigraphic units of the North American Stratigraphic Code (NACSN 2005) recognizes “Bed” or “Beds” (Flow in the case of volcanic rocks) as the only formal subdivision of members. Beds, in a geological context, are discrete depositional/accumulation units bounded by bedding planes and the formal term Bed should not be applied to thicker subdivisions of members composed of several discrete and distinguishable beds, especially of differing lithology. In such cases, thicker divisions of members that may contain one or more formally named Beds, would be usefully assigned to the division termed “Submember”. In this paper we review the issue, discuss the justification of formalizing submembers, and propose a formal amendment to the North American Stratigraphic Code.
There are several advantages to formalizing this additional division. First, submembers are already being used informally in many units. Formalization of the concept would require that these divisions meet the same standards as other stratigraphic units, e.g., designated
type sections and careful specification of boundaries. Second, the formal use of Submembers would avoid the confusing issue of having a formally named “Bed” within an interval termed “Beds”. Third, the addition of an intermediate rank permits accurate communication and precise correlation of complex sedimentary successions. The insertion of the rank of submember would allow retention of existing formal members and beds, rather than promoting the addition of new members to replace overly thick intervals formally named beds

1 aBrett, Carlton, E.1 aPratt, Brian, R.1 aLanding, E. uhttp://www.micropress.org/microaccess/stratigraphy