Abstract Carbonate eolian deposits are interbedded with shallow-marine limestones in the Ste. Genevieve Limestone in southern Indiana and northern Kentucky. Eolian grainstones can be distinguished from marine grainstones on the basis of sedimentary structures and petrographic characteristics. Eolian grainstones occur in four separate intervals in the formation. Subaerial exposure surfaces, as revealed by brecciation, rhizoliths, and calcrete, are usually at the tops of eolianites. Some exposure surfaces are not accompanied by eolian deposits, indicating that eolianites are discontinuous. At least seven shoaling-upward cycles (0 to 12 m thick) bounded by marine-flooding surfaces occur in the Ste. Genevieve and upper St. Louis Limestones in this area. Individual cycles can be correlated along the outcrop belt for at least 50 Ion and for at least 20km across the outcrop belt and in nearby cores. The base of a cycle is marked by a flooding surface as indicated by marine sediments above an eolian unit or exposure surface. The basal beds are typically carbonate mudstones or wackestones (in some cases dolomitized), which probably formed in the deepest envLronment. These micrite-ricb deposits typically are overlain by oolitic, skeletal, or peloidal marine grainstones or packstones, which probably formed as shoal or beach deposits. These are in many cases topped by an exposure surface as indicated by brecciation, rhizoliths, and rare calcrete stringers. The upper unit in four of the cycles is an eolian deposit that commonly has rhizoliths and calcrete stringers at the top and in some locations within the deposit. The upper boundary of the cycle is marked by another marineflooding surface. In some cases eolian deposits are missing from the cycle, probably because of nondeposition. Eolianites and exposure surfaces formed during falls in relative sea level. Sea-level fluctuation may have been caused by eustatic changes related to the early stages of late Paleozoic glaciation, but local teclonism cannot be disproved. Eolian deposits reach their maximum known thickness of about 6 m in the Corydon area and gradually thin to zero to the west and north.

Abstract Cross-bedded oolitic grainstones in the Ste. Genevieve Limestone (Mississippian) of the Illinois basin have generally been considered to be shallow marine. However, fine- to medium-grained cross-bedded grainstones of mixed clast type in the Ste. Genevieve of Harrison County, southern Indiana, are here interpreted to be of eolian dune origin on the basis of small-scale sedimentary structures, particularly climbing-wind-ripple structures. In addition, subaerial exposure of surfaces at the tops and bases of the eolian units is indicated by pedogenic features such as in-situ breccias and rhizoliths. Associated skeletal and oolitic grainstones of marine origin are distinguished from the eolian grainstones by the presence of pebble-sized fossils. The presence of several intervals of eolian deposits in the Ste. Genevieve is probably a result of eustatic sea level fluctuations.

Abstract The Merced Formation and consanguineous superjacent strata are well exposed in seacliffs that extend 4.3 mi (7 km) south from Lake Merced to the trace of the San Andreas fault (Fig. 1). The exposures can be reached by walking south along the beach from oceanfront public parking areas west of Lake Merced or via several well-defined trails that lead to the beach from Fort Funston (Fig. 1), a part of the Golden Gate Recreational Area, which provides public parking. The southern part of the exposure can be reached by walking north from a public parking area at Mussel Rock (Fig.1), which can be reached via an access road from Westline Drive in northern Pacifica (Edgemar). The central part of the exposure is presently accessible via a road to the former Thornton Beach State Park at the western end of Alemany Boulevard. This road, however, is now badly disrupted by landslides and affords uncertain future accessibility. The character of the exposure changes as a consequence of local landsliding and seasonal variation in the level of beach sand. The deposits are best viewed following winter storms when the erosion of beach sand provides for fresh, wave-washed exposure. The observer of these deposits should continually be alert forrock falls and the possibility of being isolated by arising tide.

Abstract The outcrops described in this report are in the vicinity of Cape Sebastian, Curry County, Oregon (Fig. 1). The principal outcrop (Point A, Fig. 2) is in the Cape Sebastian Sandstone as restricted by Bourgeois (1980), at the south tip of the Cape Sebastian headland. Visitors can most easily reach the outcrop by a 1.2-mi-long (2 km) foot trail that leads down to the south tip of the headland from the parking area at the south end of the road through Cape Sebastian State Park (Point B, Fig. ). The entrance to the state park is on U.S. 101, 6 mi (10 km) south of Gold Beach, Oregon. The outcrops of the Hunters Cove Formation of Dott (1971) are located along the shore of Hunters Cove and can most easily be reached by walking northward along the beach from the parking area alongside U.S. 101 just south of the cove (Point C, Fig. ).

Abstract The Merced Formation and consanguineous superjacent strata are well exposed in seacliffs that extend 4.3 mi (7 km) south from Lake Merced to the trace of the San Andreas fault (Fig. 1). The exposures can be reached by walking south along the beach from oceanfront public parking areas west of Lake Merced or via several well-defined trails that lead to the beach from Fort Funston (Fig. 1), a part of the Golden Gate Recreational Area, which provides public parking. The southern part of the exposure can be reached by walking north from a public parking area at Mussel Rock (Fig.1), which can be reached via an access road from Westline Drive in northern Pacifica (Edgemar). The central part of the exposure is presently accessible via a road to the former Thornton Beach State Park at the western end of Alemany Boulevard. This road, however, is now badly disrupted by landslides and affords uncertain future accessibility. The character of the exposure changes as a consequence of local landsliding and seasonal variation in the level of beach sand. The deposits are best viewed following winter storms when the erosion of beach sand provides for fresh, wave-washed exposure. The observer of these deposits should continually be alert forrock falls and the possibility of being isolated by arising tide.

Abstract The outcrops described in this report are in the vicinity of Cape Sebastian, Curry County, Oregon (Fig. 1). The principal outcrop (Point A, Fig. 2) is in the Cape Sebastian Sandstone as restricted by Bourgeois (1980), at the south tip of the Cape Sebastian headland. Visitors can most easily reach the outcrop by a 1.2-mi-long (2 km) foot trail that leads down to the south tip of the headland from the parking area at the south end of the road through Cape Sebastian State Park (Point B, Fig. ). The entrance to the state park is on U.S. 101, 6 mi (10 km) south of Gold Beach, Oregon. The outcrops of the Hunters Cove Formation of Dott (1971) are located along the shore of Hunters Cove and can most easily be reached by walking northward along the beach from the parking area alongside U.S. 101 just south of the cove (Point C, Fig. ).

Abstract This field-trip guidebook discusses the Merced Formation (of Pliocene and Pleistocene age) in its type section (Lawson, 1893) and associated Pleistocene beds in the same sea-cliff outcrops. The outcrops extend from Mussel Rock on the south to Fort Funston on the north (Fig. 1A). This section is notable for its thickness and excellence of exposure and for the wide variety of shallow marine and coastal depositional environments represented. Although the section contains a potentially important record of changes in relative sea level, the record has not yet been fully interpreted because of a dearth of precisely dated horizons. On this field trip we will proceed stratigraphically upward through the section, starting at Woods Gulch, proceeding northward past Thornton Beach State Park (presently closed because of landsliding and gullying), and ending at the northwest corner of the old Fort Funston military reservation, now part of Golden Gate National Seashore (Fig. 1A). We will not see the lower part of the section between Mussel Rock and Woods Gulch. Although the exposures are often excellent where newly eroded by ocean waves, they tend to disappear rapidly because of landsliding and sand deposition on the beach. Because of the rapid changes, all the features described in this guidebook cannot be expected to be seen at any one time. The exposures are usually best at the base of the sea cliffs in winter, when much of the beach sand has been removed by erosion. The Merced Formation and associated Pleistocene beds crop out in a belt that trends northwest-southeast for a distance of 25 km across the northern San Francisco Peninsula (Fig. IB).

Abstract The continuous southern Sacramento-northern San Joaquin Basin shoaled from minus 1000 m to sea level during deposition of 2 km of deltaic, slope, and submarine fan deposits during the Maastrichtian Epoch of theLate Cretaceous Period. Basin filling was accomplished by a combination of 1) progradation of sandy deltas and muddy slopes, and 2) aggradation of mostly sandy submarine fans. The basin filled from north to south as fluvial systems flowing southwest out of the Sierra Nevada built a deltaic complex that prograded more rapidly in the Sacramento Basin, filling it before more stable deltas to the south could fill the San Joaquin Basin. As the Sacramento Basin became filled, the fluvial-deltaic systems turned more southerly and prograded into the San Joaquin Basin. Deltaic systems consist of 1) prodelta shale, 2) upward-coarsening delta-fron sandstone, 3) delta-plain carbonaceous shale and lignite and upward-fining distributary-channel sandstone, and 4) very fine-grained (transgressive) shelf shale. Slope systems consist of 1) hemipelagic shale, 2) massive to upward-fining slope-channel sandstone, and 3) slump deposits. Submarinefan systams consist of 1) thick-bedded, upward-fining upper-fan-channel sandstone, 2) medium-to thick-bedded, massive- to upward-fining middle-fan sandstone and shale in discrete packets separated bby thin shale beds, and 3) thin- to medium-bedded, lower-fan fine-grained sandstone and shale in discrete packets separated by shale.

Abstract Local middle Eocene tectonic activity within the southern Sacramento Basin divided it into eight deposltlonal provinces during deposition of the Domenglne Formation. These provinces include the 1) Southeastern Channel Area, which grades laterally (southwest) to the 2) Southern Marsh Area and offshore (northwest) to the 3) Northeastern Bar Area. This latter area grades still farther northwest to the relatively stable 4) Northwestern Shelf Area, but was disrupted by active faults Into the subsident 5) Rio Vista Basin and 6) Sherman Island Trough to the west and southwest. This subsldent region was bordered on the south by the 7) Mt. Diablo Uplift and on the west by the 8) Kirby Hills Uplift. The Domenglne can be divided into eight distinct members, not all of which are present in each depositional provinee. Sedimentary facies within the eight members of the Domengine include 1) upward-fining coarse-to fine-grained sandstone beds, 2) upward-coarsening bar or delta-front/shoreline sandstone beds, 3) foramin perferal shelf shale, 4) carbonaceous marsh deposits, 5) fIaser-bedded subtidal deposits, 6) shelf sandstone, and 7) fluvial conglomerate and sandstone. The Domengine Formation is probably a tide-wave-dominated deltaic system. Although marine processes were Important in controlling the types and distribution of grain sizes and sedimentary structures, the overall sediment distribution system and resulting formational geometry were controlled by tectonics and subsidence related to the growth of the Stockton Arch, sediment compaction in the Meganos Gorge (submarine canyon), active faulting, and distribution of basin-margin up lifts.

Abstract A late Paleocene -early Eocene submarine canyon and fan complex, the Meganos Formation (or “Channel”) is exposed in the homoclinal sequence of Mesozoic to late Eocene age sediments that form the northern flank of Mount Diablo. Along this outcrop, the Meganos Formation comprises a narrow belt, 16 km long and one km wide. Exposures of the canyon-fill mudstones are largely masked by the alluvium of Deer Valley, but the resistant sandstones and conglomerates of the fan are well exposed along the southwest ridge flanking the valley. Canyon fed sediments spilled onto the late Paleocene -early Eocene basin floor(?) and subsequently filled the lower canyon. These sediments may be divided into two facies: (1) a lower submarine fan facies of coarse-grained clastic material; and (2) an upper mudstone canyon-fill sequence. The submarine fan facies is particularly well exposed from its basal contact, which unconformably overlies the lower Paleocene Martinez Formation, to the base of the overlying mudstone or canyon-fill facies. Within this basal sequence, fan channels are filled with disorganized conglomerates and pebbly sandstones. Boulders over 2 m in diameter are the largest clasts found in the basal channel-fills near Oil Creek. The canyon fan sequence fines vertically upwards in general aspect from basal inner fan channels to the thin sandstones of the outer fan facies and finally the mudstone of the basin plain(?) and fill. Based upon palinspastic reconstructions a minimum wall height of the submarine canyon in the vicinity of the inner fan is estimated to have been 800 m. The submarine fan was 450 m thick and the overlying mudstone of the canyon-fill facies was at least 675 m thick. The series of north-trending high angle normal faults that cut the outcrop belt are dated as Maastrichtian-earliest Paleocene to middle Eocenein age. Palinspastic restoration of Paleocene and lower Eocene units demonstrates uplift to the east, west and possibly south during this time. Uplift related to the normal faulting controlled the position of the submarine fan system and possibly the canyon. The location of the early Paleogene Meganos and underlying Martinez canyon-fan complexes and younger (Eocene) canyons in the deepest portion of southwest tilted graben that forms the Sacramento basin suggests regional and long term tectonic control. Perhaps this southern basin edge was bounded by an ancestral Stockton Arch-Mt. Diablo uplift. This major tectonic feature may be the expression of a change of subduction rate or direction of the Early Tertiary trench system.

Abstract This field trip examines spectacular exposures of sedimentary serpentinites that occur in contrasting tectonic regimes of the Neogene transform-dominated San Joaquin Basin and the late Mesozoic forearc of the Great Valley Sequence, Sacramento Valley (Fig. 1). Emphasis will be on depositional mechanisms which range from intrusive/extrusive protrusions to detrital accumulations, in subaerial to deep marine environments. The interplay between tectonic events and the deposition of sedimentary serpentinite will be stressed. For it is this interrelationship--the tectonic mobilization of serpentinized ultramafic masses from deep structural levels, their forceful protrusion to the surface, and the generation of active extrusive serpentinite flows into the sedimentary environment--that underscores the importance of these deposits in the stratigraphic record. Voluminous, monomineralic accumulations of serpentinous strata, such as the Big Blue Formation and the foliate breccias of the Wilbur Springs area, should be viewed not merely as compositional curiousities but rather as unique sedimentologic responses to tectonic events. The first day we will examine homoclinal exposures of the Big Blue Formation along the west side of the central San Joaquin Valley (Fig. 1). Six stops are planned in the Big Blue serpentinous strata. In the southern portion of the area between Anticline Ridge and Domengine Ranch, recent work by Bate describes interfingering of distal alluvial fan and tidal flat environment. Dickinson and Casey's (1976) descriptions and discussion of the Big Blue Formation in the area near Cantua Creek are recapitulated. North of Martinez Creek, they recognize a main body of subaerial protrusive serpentinite than can be traced along strike into fringing alluvial aprons that grade, with increasing distance from the source protrusion, into shallow marine facies.

Abstract The generally homoclinal eastern flank of the Diablo Range along the west side of the San Joaquin Basin of California (Fig. 6) is modified by a series of en echelon folds. One of these folds, the Coalinga anticline, is the southeast plunging extension of the Idria (or Joaquin Ridge) uplift, cored by a large serpentine diapir (Eckel and Myers, 1946). In Miocene time, basin margin shallow-marine and non-marine environments interfingered in the area of Coalinga anticline depositing a sequence of siliciclastic sediments. This lithological pattern was interrupted, when a major episode of diapiric movement extruded an enormous volume of serpentine foliate breccia, eroded the previously deposited sediments, and provided a source for sedimentary serpentinite in the same near-shore environments (Dickinson and Casey, 1976). These serpentinite deposits together make up the Big Blue Formation. The initial development of the Diablo uplift of serpentinite and Franciscan rocks occurred in post middle Eocene time (Nilsen and others, 1974), changing the continental margin from an open shelf to a partially enclosed basin. Subsidence followed (Hackel, 1966). The resulting transgressive middle Eocene Domengine Formation is the first Franciscan-derived sediment in this area (Dickinson and others, 1979). It is conformably overlain by the siliceous and calcareous shales of the Kreyenhagen Formation, which are up to a thousand meters thick (Wilson, 1943). Through the Oligocene and early Miocene, uplifts and growth of Coalinga anticline resulted in numerous angular unconformities in the Vaqueros Formation. During the Saucesian the whole northern end of the basin was subjected to 300 to 600 meters of shoaling (Bandy and Arnal, 1969), resulting in a widespread unconformity above the Vaqueros, and exposing the Kreyenhagen Formation along the flanks of the Diablo uplift.

Abstract The Big Blue Formation conformably overlies the Temblor Formation along the northeast flank of the Coalinga anticline, but is progressively truncated beneath the late Miocene Santa Margarita Formation. The near continuous exposures of yellow, orange, brown, red, and blue sediments are almost exclusively composed of detrital serpentinite. Several authors (Eckel and Myers, 1946; Cowan and Mansfield, 1970) noted the proximity of the thickest Big Blue exposures to the large (19 × 6 km) serpentine body atop San Joaquin Ridge, near the mining town of New Idria, and suggested a relationship between the two. This inferred, but poorly understood relationship between the technically emplaced serpenti nite mass at New Idria, exposed up-plunge from the San Joaquin-Coalinga anticline and the sedimentary serpentinite, was significantly clarified by Dickinson and Casey,(1976). They recognized the non-detrital character of much of the Big Blue Formation and distinguished a chaotic facies that represents protrusive serpentinite flows that resulted from massive protrusive emplacement of serpentine, associated with a major episode of diapiric movement. The major uplift occured in late middle Miocene (Luisian) time, depositing between 5 and 10 cubic miles of serpentinite debris (Eckel and Myers, 1946). Dickinson (1966) likewise called upon extrusive sheets of serpentine to explain similar deposits to the south on Table Mountain, west of Reef Ridge. The upper Temblor Formation is grey-green silty claystone overlain by 22 m of an increasingly coarse sand and pebble interval. The lowest 5 m are very fine-grained sandstone, planar bedded with thin silt-stone layers. The next 3 m are generally medium-grained sandstone, with wel 1-cemented si Itstone inter-beds.

Abstract Coalinga Oil Field (Fig. 11) has been oil and gas productive from the Temblor Formation on Coalinga anticline and the contiguous homocline to the southeast since the early part of this century. Oil was first discovered in 1890 in the Oil City area in Upper Cretaceous strata, up-plunge from the present Coalinga Field (Anderson, 1952). Development of the Eastside and Westside Fields began in 1900 and 1901 respectively, close to the Oil City area, but soon spread north, south, and southeast to the limits of the field (Anderson, 1952). The producing area is divided into the Eastside Field on the crest and flanks of the plunging anticline, and the Westside Field along the homocline into the apex of the Coalinga syncline (Kaplow, 1945). Approximately 98% of oil production in the Coalinga Oil Field is from the Temblor Formation (Cal. Oil and Gas Fields, Maps and Data Sheets, 1960), although recent efforts have been directed toward the shallower Etchegoin Formation (Taschman, 1982). Trapping is accomplished by a combination of structural and strati graphic mechanisms. The structural configuration of Coalinga anticline and its position up-dip from the Buttonwillow depocenter through much of the Tertiary (Zieglar and Spotts, 1978) resulted in migration of oil to the Coalinga Field. Zieglar and Spotts (1978) suggested that hydrocarbon generation occurred in Tertiary beds of the depocenter within the last few million years (perhaps 5 m.y.), but other structures “competing” for the oil, such as the Kettleman Hills, only developed during the Pleistocene episode of folding (Harding, 1976). The Temblor is overlapped by the Monterey and Etchegoin Formations along the Westside Field and is not exposed.

Abstract Between Anticline Ridge on the south and the Ciervo Hills on the north, serpentinous strata of the Big Blue Formation lie strati graphically between Middle Miocene Temblor Formation and Upper Miocene Santa Margarita Formation in homoclinal exposures of Tertiary strata that flank the western margin of the Great Valley. Mapping of three distinctive lithologic units within the Big Blue Formation near Cantua Creek defines key aspects of its unusual origin (see Fig. 30). Foliate but unstratified serpentinite breccia, thickest on the outcrop between Salt and Martinez Creeks, forms the body of a protrusive serpentinite extrusion that flowed as a sheared mass across an unconsolidated substratum of Temblor sand, which was partly scraped away beneath the mass-flow and was locally plowed into chaotically rumpled folds that piled up at the advancing margin of the protrusive mass. Bedded serpentinite-clast conglomerates and breccias, with intercalated serpentine-grain sandstones and associated serpentinous debris-flow deposits, were formed by fluvial reworking of the protrusive serpentinite. Detrital serpentinite locally underlies but more commonly overlies and most typically flanks the latter as a facies equivalent. Interbedded serpentine-grain sandstones and serpentinous claystones of probable marine origin exposed laterally along strike apparently formed as an extensive facies fringe of serpentinite detritus dispersed widely from a central core of protrusive and coarser detrital serpentinite. Santa Margarita beds rest conformably on the finer detrital serpentinite but uncon-formably on protrusive serpentinite and associated deposits. Easterly paleocurrents from clast imbrications in detrital serpentinite suggest that the serpentinite source lay west of the present outcrop belt. Dispersal of serpentinite debris perhaps was fed by protrusive diapiric movement of Mesozoic serpentinite mobilized in the core of an ancestral Joaquin Ridge anticline, whose initial growth thus may have coincided with the Miocene onset of rapid motion along the late Cenzoic San Andreas fault system.