WATER DEPTH INDICATIONS FROM LATE CRETACEOUS MOLLUSKS, SANTA ANA MOUNTAINS, CALIFORNIA
LouElla R. Saul Department of Earth & Space Sciences University of California, Los Angeles 90024
ABSTRACT The extensive boring, the eroded aspect to many frag- ments, the attached oysters, etc., all suggest accum- Water depths inferred from mollusks suggest very ulations of dead shells on the sea floor. Separation shallow water for the lower Baker Canyon Member, of bivalve shells under such conditions is due more deepening to middle and outer shelf for the lower to decay of ligament with time than to extensive Holz Shale Member. Molluscan remains are rare transport. through most of the Holz Shale. Mollusks indicative of outer to shallow shelf depths are present in the AGE upper Holz Shale and indicate shoaling. The Schulz Member apparently lacks mollusks. Overlying the Age of the Cretaceous sediments is shown on the Schulz is the lower Pleasants Member which has a shal- column (Fig. 1A). A late Turonian age for the Baker low shelf fauna. This is succeeded up-section by a Canyon Member and basal Holz Shale in indicated by slightly deeper shelf fauna. Two transgressions and the ammonites Subprionocyclus normalis (ANDERSON) a regression are thus suggested by the mollusks of and S. cf. S. neptuni (GEINITZ). In addition, most late Turonian to late Campanian age in the Santa Ana of the late Turonian species also occur in the Melton Mountains, Orange Co., California. Sandstone in the Redding area, Shasta Co., California. The Melton Sandstone is dated as late Turonian (Jones, INTRODUCTION SI iter, and Popenoe, 1978, p. XXI 1.3). An armionite, Canadocevas? sp. or Nowakitesl sp. from UCLA loc. Popenoe (1942) published a check list of mollusks 69152 suggests Santonian or early Campanian age for from the Late Cretaceous sediments in the Santa Ana beds below the middle of the Holz Shale. The upper Mountains which indicated abundant, common, and rare third of the Holz Shale is dated as early Campanian species from 57 localities. A paleoecologic inter- by Turritella ohiooensis holzana SAUL MS, Svibmorton- pretation of these collections and 20 others, predomi- icevas ohiooense (TRASK), and Canadoceras cf. C. nantly utilizing common and abundant species from yokoyamai (JIMBO). The uppermost Holz Shale is con- these collections, suggests a shallow, warm-water sidered to be of mid Campanian age (Saul, in press) fauna from sandstones of the Baker Canyon Member where it carries Ticcvitella chiooensis GABB. grading into a deeper, cooler-water fauna in the Pleasants Sandstone collections contain Metaplaoenti- lower Holz Shale. Above a relatively unfossiliferous oeras cf. M. paoifioum (SMITH) and are of late interval a similar molluscan fauna reappears, and Campanian age. There is no megafaunal evidence for again collections indicate grading into deeper water. beds of younger than late Campanian age in the northern Santa Ana Mountains. Most of the collections analyzed are from fos- sil iferous lenses or beds. In general the matrix at FAUNAL ANALYSIS these localities is indurated, and specimens must be broken out, thus making an accurate counting of fossil Stratigraphic position of the faunas is indicated content in a given volume impossible. For every bi- on Figure 1A and their interpreted relative water valve recovered, five are doubtless broken. Because depth is graphed on Figure 1C. Geographic distribu- of the difficulty of recovery, specimens of a less tion of the faunas is suggested by Figure IB. The common species receive priority over those of the localities are plotted on the outcrop map by fauna! more common ones, thus further skewing the count. symbol. Although the percent of forms in common Recovery of specimens is random. The volume of rock between deep and shallow water faunas is less than collected at the localities has varied greatly. The 50 per cent, there is a gradation from shallow to number of specimens recovered from any volume has de- deeper shelf faunas, and the deepest shallow-water pended as much on quality of preservation as upon the faunas could have been assigned to the moderate depth number of fossils in the rock. Species in these un- catagory. All of the faunal boundaries are similarly systematic samples have been subjectively divided somewhat arbitrary, as can be seen on the abridged into categories of abundant, common, or rare. check lists (Figs. 2 and 3). Listed are all abundant and common forms; some rare ones whose presence seems As most of the bivalves occur as single rather ecologically notable have also been listed. than paired valves, it is possible that the shells were transported and thus the site of deposition is Shallow Shelf Fauna of Late Turonian Age (#) not the site of habitation. At most localities the rock contains both relatively complete shells and Collections from the basal Baker Canyon Member shell fragments. Both shells and fragments are com- are of low diversity (See Figure 2). They are char- monly bored by more than one kind of endolith. It is acterized by common to abundant Alleinaein sulcata frequently possible to determine by the degree of (PACKARD), Liopistha ccnaana (ANDERSON), and boring which side of a shell lay upon the sediment. "Actaeonella" oviformis GABB. Trigonarca oalifovnioa Attached oysters and in some cases bryozoan colonies PACKARD is also common to abundant, but is not limited further indicate which side of a shell lay facing-up. to this fauna. Where Alleinaein sulcata is rare or
in Bottjer, D.J., Colburn, I.P., and Cooper, J.D., eds., 1982. Late Crataceom Depoetfaaal EnvfrimniU nd Paleageograpliy, Suti Ana Moaatahn, Southern C«WmiiUI Pacific Section, SEPM, Field Trip Volume and Guidebook, pg. 69-76. 69 70 absent, Flaventia zeta POPENOE is common to abundant. Deeper Shelf Fauna of Late Turonian Age (fl) Except for "Aataeonella" oviformis the mollusks were probably suspension feeders. "Aataeonella" has been This grouping consists of a few localities from considered to be an opisthobranch by Kollmann (1967), the lower siltierpart of the Holz. Faunal diversity able to inhabit somewhat brackish water, but Popenoe is moderate, about the same as that of the moderate- (pers. comm.) considered it to be a neogastropod depth shelf assemblage (See Figure 2). Of the related to Oliva. The thick shells are invariably Tethyan forms only Trigonaraa aalifomiaa remains. worn as though rolled about by wave action. "Aataeon- Characteristically present are Opis cf. 0. triangu- ella" oviformis, Trigonaraa aalifomiaat and lata (COOPER), Eriphyla ovoides PACKARD, and Liopistha anaana are not part of the usual North Clisoaolus aorrugatus POPENOE. As in the moderate- Pacific fauna but are related to Tethyan groups. depth shelf fauna, Crassatella gamma, Tenea cf. T.
Alleinaoin sulcata, which is thus far monotypic, may inflatas Cuaullaea (Idonearaa) gravida, Glossus delta, also be of Tethyan affinity, no other related species and Pterotrigonia klamathania are common to abundant. -- described or undescribed -- has yet been found in Turritella sp. and Flaventia zeta are rarely found. North Pacific faunas. Indogrammatodon sp. and aporrhaid gastropods, present in finer grained sediments of the moderate-depth This fauna suggests warm, very shallow water. shelf localities, are more common; and desmoceratoid "Aataeonella" oviformis may well have lived inter- ammonites, Mesopuzosia sp. and Tragodesmoaeras? aff. tidal ly, but the presence of Glyaymeris paaifiaus T. ? ashlandiaum (ANDERSON), have been collected. (ANDERSON), Synayolonema sp., Lima beta POPENOE, and Subprionocyalus spp. suggests that the fauna pre- Mollusks of this assemblage probably inhabited dominantly inhabited shallow sublittoral areas. deeper depth shelf areas. Some of the faunal change is probably due to finer grained substrate, but the Moderate Depth Shelf Fauna of Late Turonian Age (A) absence of Saaphites spp. may result from cooler, off-shore water. The weakly sculptured desmocera- Included in this grouping of fossil localities toids are suggestive of deeper water (Tanabe, 1979). are collections from the upper Baker Canyon Member and the sandier beds in the lowermost Holz Shale. Deeper Shelf Fauna of Early Campanian Age (•) These localities yield faunas at least twice as di- verse as those of the basal Baker Canyon Member. Localities yielding this fauna are predominantly Characteristically present are Turritella heami in small lenses in the upper third of the Holz Shale. MERRIAM or T. iota POPENOE, Pterotrigonia klamath- The fauna is of low to moderate diversity and con- onia (ANDERSON), Crassatella gamma POPENOE, Aphro- sists of typically North Pacific forms. The strati- dina arata (GABB), Corbula spp., Saaphites spp. and graphically lowest localities characteristically have Saiponoaeras aff. S. bohemiaum (FRITSCH)(See Figure Turritella paakardi MERRIAM and Eriphyla veatahii 2). Flaventia zeta and Ampullina pseudoalveata GABB and are of lowest diversity. Stratigraphically PACKARD, also found at shallow shelf localities, are higher localities have a moderately diverse fauna rarely present at deeper shelf localities, whereas characterized by Tixrritella ahiaoensis holzana SAUL Tenea cf. T. inflata (GABB), Cucullaea (Idonearaa) MS, Opis aff. 0. triangulata (COOPER), and Indogram- gravida (GABB), and Glossus delta (POPENOE) are matodon whiteavesi (REINHART). In addition present at deeper shelf localities but not at the Glyaymeris veatahii (GABB), Cuaullaea (Idonearaa) shallower. Collections included in the group which youngi WARING, Crassatella spp., Etea angulata are from finer grained sediments have aporrhaiid (PACKARD), Tenea inflata (GABB), Anahura cf. A. fal- gastropods Anahura aondoniana ANDERSON. Pyktes aiformis GABB, Volutoderma spp., and Bipli'aa obliqua daiphron POPENOE MS, and Arrhoges (Latiala) aalifor- (GABB) are common to abundant (See Figure 3). Early niaus (PACKARD). In sandier substrates the Campanian age is indicated by a specimen of Submor- gryphaeid oyster Exogyra sp. is common. Hetero- toniaeras ahiaoense (TRASK) and rare Canadoaeras morphic ammonites Bostryahoaeras sp. and Hyphanto- aeras aff. H. venustum (YABE) are also present. The Tethyan element of this fauna is much less than in Figure 1. A, Generalized composite columnar section the shallow shelf fauna, consisting only of Trigon- of Late Cretaceous rocks in northern Santa Ana Moun- araa aalifomioa and Saaphites spp. In Japan, Tanabe tains with molluscan fossil localities in approximate (1979) faund such strongly sculptured ammonites as stratigraphic position. Based on columnar sections Subprionoayalus sp. indicated shallow shelf environ- of Popenoe (1942) in which the fossiliferous sand- ments and heteromorphs, including baculitids, stone beds containing Turritella ahiaoensis GABB are scaphites, and nostocerids, probably inhabited mid- included in the Holz Shale Member (rather than in the shelf areas. Differences in siphuncular strength Schulz; see Bottjer, Colburn, & Cooper, this volume). suggested to him a deeper water habitat for the The Schulz Member overlies these fossiliferous beds weakly sculptured desmoceratids. disconformably (Popenoe, 1942) — to the south in the Canada Gobernadora Quadrangle, the Schulz overlaps Mollusks in these collections probably inhabited the Ladd Formation (Morton, 1974, p. 21) --, and only moderate-depth shelf areas. The change from largely one locality in the Schulz, CIT 1066, provides marine fossils. Popenoe (1942, p. 174) suggested that these Tethyan affinites to largely North Pacific affinities fossils were reworked from the Holz. B, Outcrop map suggests a drop in temperature that could result from of Late Cretaceous sedimentary rocks from vicinity of a deeper water habitat. Tanabe (1979) has suggested Black Star Canyon on the north, south to Piano Tra- that the habitat of his heteromorphic ammonites was buco. Fossil localities plotted by symbols indicate from shallow to deeper water, overlapping that of the similar faunal composition. See text for fuller shallow water collignoniceratids. Stenzel (1971, explanation of symbols (Based on map of Popenoe, p. N1040) states that the Gryphaeinae indicate open, 1942). C, Graph of probable water depth indicated by euhaline seas, and no molluscan species suggesting the molluscan faunas, based largely on occurrences of less than normal salinity was found in this group of abundant and common mollusks in Popenoe, 1942, fig. 4. collections. See Locality Map (Saul & Bottjer, this volume) for plotting of numbered fossil localities. /
71 72
characteristic species AA AA A
6953 CSULA 4550 1532
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M O_J
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0 JZa. A3 i- CT> -t-> c +-> «r— fU
Figure 2. Abridged check list of Turonian and ?Coniacian species. cf. C. yokoyamai (JIMBO). Submortoniaeras ahiooense localities resembles the deeper shelf, lower Holz resembles Subprionoayalus spp. of Turonian age and localities, but the species have changed with the probably had a similar shallow-water habitat. passage of time. The rarity of Submortoniaeras ahioo- ense in the Santa Ana Mountains collections may result In generic make up the fauna of this group of from early Campanian deposits of this area being of a rare T = species with Tethyan HOLZ SHALE SCHULZ MEMBER, PLEASANTS MEMBER common affinities H abundant localities listed in approximate strati- i graphic order (see Figure 1A) to So —' —1 Cn —' Cn OM —1 —1 —1 —1 —1 —1 O Cn OOO O O —' So —' OIOI vovotnvooon^ 455 = Calif. Inst. Tech. locality tri CTl 00 Oj CTlOo U1
At the top of the Holz Shale (=lower part of Moderate Depth Shelf Fauna of Late Campanian Age (A) Schulz Member, see Bottjer, Colburn, and Cooper, this volume, Fig. 3) are sanldstone lenses and beds with a Collections from a few localities in the upper more diverse fauna than that of the stratigraphically Pleasants Member are characterized by Turritella lower lenses yielding the deeper shelf fauna. This ahicoensis pesoaderoensis ARNOLD, Pterotrigonia fauna also consists predominantly of typically North evansana (MEEK), and Crassatella spp. The collec- Pacific forms. It is characterized by Pterotrigonia tions are of moderate diversity with bivalves Cuaul- evansana (MEEK), Crassatella spp., Cyrribophora suci- laea (Idonearaa) cordiformis PACKARD, Clisoaolus ensis (WHITEAVES), and Turritella ahiaoensis GABB. dubius (GABB), Calva bowersiana, and gastropods Common to abundant forms include Trinaaria aor Volutoderma spp., and Biplica obliqua common or abun- POPENOE, Cucullaea (Idonearaa) youngi, Clisoaolus dant. Also present are ammonites Metaplaaentiaeras dubius (GABB), Flaventia lens (GABB), Lysis spp., cf. M. paaifiaum, Baaulites sp., and Gaudryceras cf. Euspira sp., and Baaulites sp. (B. inornatus MEEK in G. (Vertebrites) kayei (FORBES)(See Figure 3). part)(See Figure 3). Metaplaaentiaeras is less abundant in these collec- tions than in the collections inferred to be from This fauna is similar to the Turonian, moderate shallow shelf areas. Gaudryceras is a tetragonitid, depth shelf fauna in generic make up (Fig. 2). Tri- and thus belongs to a group with greater siphuncular naaria aor may represent a Tethyan element in this strength (Tanabe, 1979, p. 625) and may have been fauna. The heteromorphic ammonites Pseudoxybeloaeras able to inhabit deeper water. sp., Bostryahoaeras? sp., and especially Baaulites sp. are present and perhaps suggestive of mid shelf These collections are similar in generic make up habitats. to the late Turonian and mid-Campanian moderate depth shelf faunas. Shallow Shelf Faunas of Mid Campanian Age (O) DURATION OF INDICATED WATER DEPTH A few localities at the top of the Holz Shale have more species suggestive of shallow water and Obradovich and Cobban (1975) suggest the follow- lack a few forms common at the moderate depth shelf ing stage durations: Turonian -- 3m.y., Coniacian localities. The moderately diverse fauna at these -- 1 m.y., Santonian — 4 m.y., and Campanian -- localities is, however, very similar to that of the 12 m.y. Molluscan fossils older than late Turonian moderate depth shelf. It is still characterized by have not been shown to occur in the Baker Canyon Mem- the presence of Turritella ahiaoensis and Crassatella ber. The shoreline suggested by the very shallow spp., but not by Pterotrigonia evansana. Both smooth shelf fauna moved eastward from near the present and ribbed cymbophoras, Cyrribophora suaiensis and C. confluence of Ladd and Silverado Canyons about 1.5km. popenoei SAUL, are present (See Figure 3). C. During the later third of the Turonian moderate depth popenoei and Yaadia tryoniana (GABB), which is un- faunas succeeded by deeper shelf faunas inhabited not common, are considered suggestive of shallow water only the present vicinity of the old Holz Ranch in (Saul, 1974 & 1978). Silverado Canyon but also areas 1.5 km to the east (see Figure IB). These deep shelf molluscan faunas Although referred to shallow shelf this fauna may be in part of Coniacian age if the Mesopuzosia suggests deeper or quieter water than the shallow yubarense (JIMBQ) (Matsumoto, 1959, p. 71) found in shelf fauna of late Turonian age. the Holz Shale below a conglomerate lens (Saul & Bottjer, this volume, Locality Map, UCLA loc. 6953) Shallow Shelf Fauna of Late Campanian Age (O) is correctly determined. Almgren (this volume) finds bathyal Foraminifera in beds overlying those with the Localities in the lower Pleasants Sandstone molluscan shelf fa.unas. In the present vicinity of Member of the Williams Formation have yielded the the old Holz Ranch house, the change from littoral to most diverse Late Cretaceous fauna from the Santa Ana bathyal depths may have taken two m.y. Mountains (See Figure 3). The fauna is predominantly of North Pacific affinities, but Trinaaria aor and In the upper third of the Holz, molluscan deeper Braahidontes bifuraatus POPENOE may be Tethyan shelf faunas, now of early Campanian age, again occur elements. Characteristically Cyrribophora popenoei, signalling a regression. The bathyal conditions thus Metaplaaentiaeras cf. M. paaifiaum (SMITH), and probably prevailed for a least four m.y. and the Gyrodes canadensis WHITEAVES are present. Meekia deeper shelf conditions for perhaps 3 m.y. daileyi SAUL & POPENOE and Yaadia robusta SAUL are suggestive of a shallow inner sublittoral habitat. A shallow water, but by no means littoral, fauna Additional common to abundant bivalves include Glyay- of mid Campanian age occurs at the top of the Holz, meris veatahii (GABB), Pterotrigonia evansana, Curribo- and the regression may have lasted four to five m.y. phora triccngulata (WARING), C. stantoni (ARNOLD), Calva bowersiana (COOPER), and Legimen ooides A similar shallow water fauna, but of late Cam- (GABB). The most common gastropods are herbivorous panian age, is in the lower Pleasants Member succeeded Atira ornatissimus (GABB) and probably carnivorous by a moderate depth fauna also of late Campanian age. or detritophagus "Fulgur" hilgardi WHITE, Perissitys Mollusks from Pleasants Member outcrops near Bee brevirostris (GABB), Volutoderma spp., and Biplica Canyon (Saul & Bottjer, this volume, Locality Map obliqua (GABB). sheet 1, UCLA loc. 2415) have been considered to be younger than others from the Pleasants Member (Mat- This fauna is essentially similar to the mid sumoto, 1960, p. 66) in the Santa Ana Mountains. The Campanian shallow shelf fauna. Its slight increase fauna suggests at least moderate depth. If the age in diversity may or may not suggest somewhat shallower is latest Campanian or earliest Maestrichtian (Matsu- water or even a late Cretaceous warming trend. The moto, 1960, p. 154), a late Campanian transgression ornate ammonite Metaplaaentiaeras cf. M. paaifiaum is