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

OTHER WEST COAST AREAS

OREGON

Several small basins of late Tertiary deposition are known along the Oregon coast, notably in the Coos Bay area and in the vicinity of Cape Blanco. At Coos Bay a sequence including the Empire Formation and possibly the Port Orford Formation may well correlate in some way with at least a part of the Quinault Formation. Arnold and Hannibal (1913) first suggested such a correlation basing their conclusions largely on mollusks. At that time these beds were regarded as Miocene in age, but in recent years they have been considered Pliocene in age (Allen and Baldwin, 1944; Weaver and others, 1944). Unfortunately, no foraminiferal information is available from these rocks, and therefore it is not possible in this report to contribute knowledge of the stratigraphic relation between these Oregon beds and those of the Quinault Formation.

In the vicinity of Cape Blanco, Bandy (1950) described and discussed Foraminifera from what he referred to as the Port Orford and Elk River Formations, which he regarded as middle or late Pliocene and Pleistocene in age, respectively. Most of the species listed from the Port Orford Formation are conspecific with those in some part of the Quinault Formation of this report. Possibly the greatest faunal similarity is in the Duck Creek-Pratt Cliff section, where Florilus basispirtatum is a major element in the fauna, as is the case in the Port Orford section of the Cape Blanco area. A significant variation, however is the great abundance of Elphidiella hannai in the Port Orford Formation, in contrast to only rare occurrences of the form in any part of the Quinault Formation. An appreciable number of species listed from the Elk River Formation are also present in some part of the Quinault Formation particularly those listed from the Elk River Elphidiella hannai zone, even though E. hannai is the dominant species in the Elk River assemblage also.

These foraminiferal comparisons suggest, in a general way, that similar ecological conditions may have existed during the deposition of the beds near Cape Blanco and those in at least parts of the Quinault Formation, and that, although the evidence is not conclusive, deposition of these two sequences of beds could have been, in part, contemporaneous.

NORTHERN CALIFORNIA

Along the coastal area of northern California in the vicinity of the Eel River, late Tertiary deposits known as the Wildcat group have been mapped in detail (Ogle, 1953) and Foraminifera contained therein studied rather extensively (Cushman, Stewart, and Stewart, 1930; Stewart and Stewart, 1949; Crawford, Hughes, In Ogle, 1953, p. 46). It is likely that some of these northern California beds may have been deposited penecontemporaneously with those of the Quinault Formation of the Washington coast. Cushman, Stewart, and Stewart (1949) were the first to point out the similarity in the foraminiferal fauna of part of the Quinault Formation and that of part of the Wildcat Group. At that time, they tentatively correlated these beds with a middle part of the Repetto Formation of southern California, of early Pliocene age. In the following discussion, comparisons of the foraminiferal faunas of the Wildcat Group are made with those of the four sections of the Quinault Formation of this report.

None of the assemblages of the Wildcat Group are particularly similar to those of the Duck Creek-Pratt Cliff section. However, those from a lower-middle part (lower part of the Rio Del Formation and possibly the Eel River Formation) best compare with the Foraminifera of this section.

The extremely limited assemblage of the Cape Elizabeth section is best compared with that of an upper part of the Wildcat Group (upper part of the Rio Del Formation, and the Scotia Bluffs Sandstone). In assemblages from both areas, Elphidium, such as E. hughesi, are consistently present, but mostly are not found in lower parts of the Wildcat Group. Elphidiella hannai seems to be confined to the upper part of the northern California sequence, and it is also found in the Cape Elizabeth section. Although these similarities do not necessarily indicate contemporaneity of deposition, they do suggest similar environments of deposition; namely, shallow, possibly brackish, water conditions. Such faunal assemblages dominate in the upper part of the Wildcat Group, a stratigraphic position similar to that suggested for the Cape Elizabeth section with respect to the entire outcrop area of the Quinault Formation. Furthermore, the sequence of the lithologies seen in the Scotia Bluffs Sandstone and the Carlotta Formation of the upper part of the Wildcat Group is generally similar to that of the Cape Elizabeth section of the Quinault Formation; that is, sandstone in the lower part grading up to conglomerate at the top. Ogle (1953) suggests tentative correlations of the upper part of the Scotia Bluffs Sandstone and the Carlotta Formation with "deposits at the mouth of Elk River, Oregon," and also of the lower part of the Scotia Bluffs Sandstone with a part of the Empire Formation at Coos Bay, Oregon.

Foraminifera from the section south of Taholah can best be compared with those of a middle to upper part of the Wildcat Group (mainly the Rio Del Formation). Salient faunal similarities are: the common occurrence of such forms as Cassidulina limbata, Cibicides mckannai, and low, finely costate Uvigerina; and the less common occurrence of Elphidiella hannai, Elphidium hughesi, Polymorphina charlottensis, and coarsely costate Uvigerina.

The fauna of the section north of Point Grenville probably is more like that of the Wildcat Group than are any of those from other sections in the Quinault Formation. Some of the more significant forms present in both are:

Cassidulina limbata
Cassidulina translucens
Elphidiella hannai
Elphidium hughesi
Elphidium microgranulosum
Polymorphirta charlottensis costate Uvigerina

According to available information, these forms are all largely confined to a middle and upper part of the Wildcat Group (Rio Del Formation and possibly Scotia Bluffs Sandstone).

In general summary, the foraminiferal faunas of the middle and upper parts of the Wildcat Group of northern California (Rio Del Formation and Scotia Bluffs Sandstone) best compare with those of the Quinault Formation of the Washington coast. Although these similarities do indicate comparable depositional environments, they do not necessarily indicate contemporaneous deposition. However, assuming that the Cape Elizabeth section does represent the upper parts of the Quinault Formation, the faunal sequence as well as the general lithologic sequence of the entire Quinault Formation, is broadly comparable to that of the middle and upper part of the Wildcat Group, which Ogle (1953) regards as ranging from middle to upper Pliocene in age. Others suggest that the upper part of the sequence may be Pleistocene in age (Stewart and Stewart, 1949).

SAN FRANCISCO PENINSULA

Along the coast in the San Francisco Peninsula area, a sequence of upper Tertiary-lower Quaternary deposits known as the Purisima and Merced Formations may well have been deposited during a time similar to that of the Quinault Formation. Arnold (1906), in his original discussion of the Quinault Formation, mentioned that the megafossils suggest a possible correlation of the formation to the Purisima Formation. Later, Weaver (1937) stated that megafossils from the Quinault Formation between Point Grenville and the mouth of the Quinault River [sections north of Point Grenville and south of Taholah] are closely allied with those of the Merced Formation. The Merced Formation is generally regarded as middle Pliocene through early Pleistocene in age, whereas the Purisima Formation is considered middle Pliocene in age and is possibly, in part, equivalent to a lower part of the Merced Formation (Glen, 1959).

The available information on Foraminifera from this California sequence is limited to reports on two small assemblages, one from the type Merced Formation at Seven Mile Beach (Stewart and Stewart, 1933), and the other from the Purisima Formation of the Halfmoon Bay area (Goodwin and Thomson, 1954). The best comparisons of these faunal assemblages and those of the Quinault Formation are with those of the Purisima Formation and of the Duck Creek-Pratt Cliff section. Substantially represented in both are Buliminella elegantissima, Cibicides fletcheri, Florilus basispirtatum (Pseudononionella cushmani), Uvigerina juncea, smooth Globobulimina, and Nonionella miocertica. Other forms are also present in lesser numbers in both formations.

Foraminiferal assemblages of the other sections of the Quinault Formation are not noticeably similar to those of the known faunas of the Purisima-Merced sequence. Generally then, based on limited foraminiferal information from this California sequence, the Foraminifera of the Quinault Formation are not greatly similar and therefore do not strongly support evidence for a correlation. However, the best comparison is with the Foraminifera of the Duck Creek-Pratt Cliff section and those of the Purisima Formation.

SANTA MARIA DISTRICT

Comprehensive studies of Woodring and Bramlette (1950) on the Santa Maria District of California serve as a particularly detailed source of data on the biostratigraphy of that region. It is therefore possible to make at least broad comparisons of the Foraminifera of that area with those of the Quinault Formation. Such comparisons show that noticeably more Foraminifera of the Quinault Formation are listed from the Foxen Mudstone of middle- to-late Pliocene age (Woodring and Bramlette 1950) than from any of the other units of that area. Species well represented in both the Quinault Formation and the Foxen Mudstone, and therefore the most significant with respect to a suggested correlation, are Cassidulina limbata, Elphidium hughesi, Nortionella miocenica, costate Uvigerina, and varieties of Virgulina californica. Faunas of the two sections between Point Grenville and Taholah compare somewhat more favorably with those of the Foxen Mudstone than do those of the Duck Creek-Pratt Cliff section. Notable are the presence of both E. hughesi and C. limbata in the Taholah-Point Grenville sections, and the absence of these species in the Duck Creek-Pratt Cliff section.

Similarities in faunal assemblages here again suggest that conditions of deposition may have been reasonably similar in the two areas, but only in a broad sense is it likely that the Quinault Formation, particularly the beds of the Taholah-Point Grenville sequence, correlates with the Foxen Mudstone of the Santa Maria District. It is probably more realistic to consider that these Quinault beds may represent a position in the development of the depositional sequence within the local basin similar to that represented by the Foxen Mudstone in its basin of deposition.