Washington Department of Natural Resources Bulletin No. 62 Foraminifera, Stratigraphy, and Paleoecology of the Quinault Formation, Point Grenville-Raft River Coastal Area, Washington Weldon W. Rau

SOUTHERN CALIFORNIA,
A WEST COAST STANDARD

The upper Tertiary-lower Quaternary sequence is particularly well developed in the coastal region of southern California, especially in the Ventura and Los Angeles basins, as well as in the Santa Barbara Channel area. Much of the petroleum from that region has been produced from these rocks. Largely because of this economic significance, a detailed biostratigraphic framework has been developed for these strata. It has become generally accepted as the west coast standard with which most correlations are made of upper Tertiary-lower Quaternary beds of the west coast area. Many workers have contributed to this biostratigraphic standard, but, because of its commercial aspect, much of the knowledge acquired has not been made readily available in published form. The work of Natland (1933, 1938, 1950, 1952, and 1957) and that of Wissler (1943) are among the major studies dealing with the actual biostratigraphic framework of these rocks. Ingle (1967) presented a major contribution dealing with the planktonic Foraminifera of upper Tertiary beds in southern California. Additional works, primarily concerned with taxonomy of the Foraminifera, were presented by Galloway and Wissler (1927a and 1927b), Stewart and Stewart (1930), Cushman and Gray (1946a and 1946b), Martin (1952), and White (1956). Many others have contributed to the refinement of the biostratigraphy of these rocks, although perhaps not all in published form. Numerous variations are in use among individual workers and commercial organizations with respect to precisely where boundaries are placed, but most authorities are in general agreement with a basic framework. For the purpose of comparing what is known concerning the biostratigraphy of the Quinault Formation, only a broad view of this standard framework is needed, and therefore the following summary is presented.

Pliocene beds in the Los Angeles and Ventura basins and vicinity are divided essentially into the Repetto Formation at the base and the Pico Formation at the top. Rocks assigned to the upper Miocene, such as the Puente Formation and Santa Margarita Formation, underlie the Repetto Formation; whereas the Pico Formation is overlain by beds usually assigned to the Pleistocene, such as the Santa Barbara, Saugus, and Las Posas Formations, and the Timms Point Silt and Lomita Marl. Natland (1952), in his dissertation on "Pleistocene and Pliocene stratigraphy of southern California," developed foraminiferal stages for this sequence, using the term "Repettian" to constitute the lowest stage of the Pliocene, which is essentially represented in beds of the Repetto Formation (Fig. 7, p. 13). His Venturian stage constitutes a middle part of the Pliocene and in the Los Angeles basin is represented in a lower part of the Pico Formation. His Wheelerian stage constitutes an upper part of the Pliocene and is largely represented in the upper part of the Pico Formation. The Hallian stage of Natland generally constitutes the Pleistocene, although the boundary between the Hallian and the Wheelerian stages is now placed variously in or between the Pico and overlying beds.

It has been demonstrated, particularly by the work of Natland, that the Pliocene-Pleistocene sequence in the Los Angeles basin, as well as in other basins in the vicinity, reflects a history of basin filling, both faunally and lithologically. To a large extent, faunas of the Repettian stage are those typical of substantial water depths. Succeeding faunas of the Venturian, Wheelerian, and Hallian stages largely represent progressive shoaling from bathyal to littoral depths. Basically, then, correlation of the stages of Natland and, for that matter, essentially all faunal subdivisions observed in the southern California region, are based on the similarity of the succession of ecological conditions reflected by the faunas of each basin. Local correlations, therefore, are based largely on the premise that similar successions of ecological events took place within each basin of deposition during Pliocene and Pleistocene time. However, major exceptions are most certainly to be expected because of the varieties of ecological conditions present in any basin at a given time. Natland, as early as 1933, and a number of other workers since that time have made this observation, and recently it was particularly well stated by Ingle (1967, p. 218, 219), "There is neither a ubiquitous lithology or biota characteristic of all areas at any moment;..." Nevertheless, for the purpose of broadly relating stratigraphy from basin to basin, the succession of ecological events recorded in the upper Tertiary-lower Quaternary sequence along the Washington coast, as partly represented in the Quinault Formation, could be expected to be somewhat comparable to that in other west coast upper Tertiary-lower Quaternary basins of deposition. The following suggested correlations are based on this concept and are therefore somewhat generalized.

The Duck Creek-Pratt Cliff section, together with nearby isolated outcrops, may well represent the lowest part of the Quinault Formation exposed along the coast. Its fauna (checklist, p. 20) probably best compares with that of the lower part of the upper Tertiary-lower Quaternary sequence of the Los Angeles area occurring in the Repetto Formation and possibly part of the Pico Formation. Foraminifera suggesting a correlation with beds in a relatively low position in the sequence are a few forms commonly associated with subjacent beds of the upper Miocene, such as Rotalia garveyensis, Uvigerina hootsi, and Virgulina californiensis ticensis. However, a greater number of forms from the Duck Creek-Pratt Cliff area are common to the Repetto and Pico Formations, such as Bulimina elegantissima, Cassidulina reflexa, Florilus basispinatum, Nonion miocenica, Pullenia salisburyi, Uvigerina juncea, and Uvigerina subperegrina. The few pre-Repetto forms, particularly R. garveyensis, tend to suggest that the lower part of the section may correlate with an uppermost part of the Miocene (Mohnian and Delmontian stages, undifferentiated, of Kleinpell, 1938) of the southern California sequence. However, the major part of the foraminiferal fauna probably best compares with those of the Pliocene Repetto and Pico Formations of the southern California sequence and therefore equates with the Repettian and Venturian stages and possibly even a part of the Wheelerian stage of Natland (1952).

The meager foraminiferal fauna of the Cape Elizabeth section, by itself, is hardly sufficient from which to even suggest a correlation. But, since all those Foraminifera that are present and the nature of the lithology both indicate shallow-water deposition, it is speculated that this section represents a latter stage of deposition and therefore is an upper part of the local sequence. On that basis, this section may well equate broadly with the uppermost part of the Pico Formation (late Pliocene) and possibly some of the overlying lower Quaternary deposits such as the Santa Barbara Formation, the Timms Point Silt, Lomita Marl, and Las Posas Formation of the southern California area.

Foraminifera of the section south of Taholah compare broadly with those of much of the Los Angeles sequence, including most of the Repetto Formation and the Pico Formation, and possibly even some of the overlying beds of Pleistocene(?) age. However, of those foraminiferal species present in both the Taholah section and some part of the Los Angeles sequence, noticeably more are known to be present in the Pico Formation. Of these, the following are probably most significant because they are well represented in the Taholah section:

Cassidulina limbata
Cibicides mckannai
Elphidium hughesi foraminosum
Uvigerina subperegrina

Even though the evidence is not at all strong, Foraminifera from the Taholah section best compare with those of the middle part of the Los Angeles sequence of late Tertiary-early Quaternary deposition, and therefore probably best relate to the Venturian and Wheelerian stages of Natland (1952).

The section north of Point Grenville also contains a number of forms common in the southern California upper Tertiary-lower Quaternary sequence. Some of these are particularly common to the Pico Formation, a few of which are known to extend into the overlying rocks of probable Pleistocene age, and others down into the underlying Repetto Formation. Possibly most significant because of their abundance in the Point Grenville section are the following forms:

Cassidulina limbata
Cassidulina reflexa
Elphidium microgranulosum
Florilus basispirtatum

Although the evidence is not all conclusive, Foraminifera of this section of the Quinault Formation also best compare with those of the Pico Formation of southern California, and perhaps relate to the Wheelerian and possibly lower part of the Hallian stage of Natland (1952).

In general summary, the foraminiferal sequence of the four measured sections of the Quinault Formation compare in a broad way with that known in the Repetto-Pico sequence of the Los Angeles area and vicinity. Although the evidence is not at all conclusive, the lowermost part of the Quinault Formation of this report may equate to rocks of late Miocene age, and the uppermost part of the formation to beds thought to be as young as early Pleistocene in age in the Los Angeles area (Fig. 7, p. 13).