Abstract Regional seismic mapping identified lower and middle Miocene slope channels as significant exploration targets for Angola Block 15. Seventeen exploration wells, followed by four appraisal wells, established these slope-channel complexes as a world-class development opportunity. ExxonMobil's current development activity targets stacked turbidite-dominated reservoirs in long-reach, high-angle wellbores tied back to tension leg platform (TLP) and close-moored floating production, storage, and offshore loading facilities. One of the major development targets in Block 15 is the Burdigalian-aged (Bur1) slope-channel reservoirs. The Bur1 slope-channel system was one of many lower Miocene sediment fairways that provided a mechanism for the delivery of coarse-grained turbidites and mixed muddy and sandy debrites into the Lower Congo basin. This slope-channel system traverses across the block in an east-west direction and can be continuously mapped on adjacent seismic data sets across a 30-40-km (18-25-mi) reach. Three conventional cores and 28 well penetrations calibrate updip to downdip changes in lithofacies type and channel architecture. Map patterns of the Bur1 slope-channel system show distinctive changes in sinuosity, channel confinement, and degree of amalgamation broadly related to concurrent growth of salt-related structures. Channel-complex confinement is more pronounced, and vertical amalgamation is better developed in segments that cross structural highs. The Bur1 channel system shows weaker lateral amalgamation, greater sinuosity, and less erosional confinement in structural lows. The episodic fill of the Bur1 slope-channel system can be better understood by a hierarchical arrangement of unconformity-bounded stratal units. Within these unconformity-bounded channel sets, nested channels form composite channel complexes that show distinctive trends in lithofacies type and vertical facies succession. Compared to other offshore Angola slope-channel systems, this Bur1 system is noteworthy because of the relatively coarse granule to cobble grain sizes encountered. Well logs and high-resolution seismic data calibrated to conventional cores show that the lower parts of the channel complexes are dominated by sandy-muddy debrites, slumps, and injected sandstones. These facies are typically overlain by coarse-grained, gravelly, and well-amalgamated sandy turbidites. The overlying facies succession is more variable, but commonly consists of interbedded sandy and muddy turbidites, injected sandstones, and a range of both muddy and sandy debrites.

Abstract Exceptional oblique-dip exposures of submarine fan complexes of the Brushy Canyon Fm. allow reconstruction of channel geometries and reservoir architecture from the slope to the basin floor. The Brushy Canyon conslsts of 1,500 ft. of basinally restricted sandstones and siltstones that onlap older carbonate slope deposits at the NW margin of the Delaware Basin. This succession represents a lowstand qequence set comprised of lugher frequency sequences that were deposited in the basin during subaerial exposure and bypass of the adjacent carbonate shelf. Progradational sequence stacking patterns reflect changing position and character of the slope as it evolved from a relict, carbonate margin, to a constructional, siltstone-dominated slope. Lowstand fan systems tracts consist of sharp-based, laterally extensive, sand-prone basin floor deposits and large, sand-filled channels encased in siltstones on the slope. The abandonment phase of each sequence (lowstand wedge-transgressive systems tract) consists of basinward-thinning siltstones that drape the basin floor fans. The slope-tobasin distnbution of lithofacies is attributed to a three stage cycle of: 1) erosion, mass wasting, and sand bypass on the slope with concurrent deposition from sand-rich flows on the basin floor, 2) progressive backfilling of feeder channels with variable fill during waning stages of deposition, and 3) cessation of sand delivery to the basin and deposition of laterally-extensive siltstone wedges. Paleocurrents and channel distributions indicate SE-E sediment transport from the NW basin margin via closely spaced point sources.

Abstract Exceptional oblique-dip exposures of submarine fan complexes of the Brushy Canyon Fm. allow reconstruction of channel geometries and reservoir architecture from the slope to the basin floor. The Brushy Canyon conslsts of 1,500 ft. of basinally restricted sandstones and siltstones that onlap older carbonate slope deposits at the NW margin of the Delaware Basin. This succession represents a lowstand qequence set comprised of lugher frequency sequences that were deposited in the basin during subaerial exposure and bypass of the adjacent carbonate shelf. Progradational sequence stacking patterns reflect changing position and character of the slope as it evolved from a relict, carbonate margin, to a constructional, siltstone-dominated slope. Lowstand fan systems tracts consist of sharp-based, laterally extensive, sand-prone basin floor deposits and large, sand-filled channels encased in siltstones on the slope. The abandonment phase of each sequence (lowstand wedge-transgressive systems tract) consists of basinward-thinning siltstones that drape the basin floor fans. The slope-tobasin distnbution of lithofacies is attributed to a three stage cycle of: 1) erosion, mass wasting, and sand bypass on the slope with concurrent deposition from sand-rich flows on the basin floor, 2) progressive backfilling of feeder channels with variable fill during waning stages of deposition, and 3) cessation of sand delivery to the basin and deposition of laterally-extensive siltstone wedges. Paleocurrents and channel distributions indicate SE-E sediment transport from the NW basin margin via closely spaced point sources.

Abstract OBJECTIVES: The Lower Sego provides an opportunity to study well-exposed, high-frequency sequences and their systems tracts. Criteria for identification of sequence boundaries will be presented. Sequences and their boundaries will be contrasted with parasequences and their bounding surfaces. The Upper and Lower Sego contain well-exposed tidal deposits within the lowstand systems tracts of high-frequency sequences. These tidal deposits and their relationship to incised valleys and systems tracts will be examined. The incised valleys interpreted to form during relative falls in sea level will be contrasted with distributary channels related to autocyclic mechanisms. 0.0 Leave the parking lot of the Grand Junction Hilton, Grand Junction, Colorado. Turn left onto Horizon Drive. Pass under the 1-70 bridge. Turn left onto the entrance ramp for 1-70 west. 0.2 Enter 1-70 heading west toward the Colorado-Utah State line. For the next 20 miles the Interstate will parallel the Colorado River flowing along the west side of the Grand Valley. The Interstate is built on the gray Cretaceous Mancos Shale. To the west of the Colorado River are the red cliffs of the Colorado National Monument. The Monument is operated by the National Parks Service. These cliffs are the eastern edge of the Uncompahgre Uplift As you drive north along the Interstate, the steeply dipping eastern limb of the Uncompahgre is clearly visible. This tight monoclinal fold is the result of horizontal compressional tectonics associated with Laramide deformation (Heyman, 1983). The red rocks in the Monument include, from stratigraphically oldest to youngest: the Chinle Formation

Abstract The Lower Sego, Anchor Tongue of the Mancos Shale, and the Upper Sego are well exposed along the Book Cliffs in western Colorado and eastern Utah. For the most part these strata crop out on public lands and access is excellent due to the constantly maintained roads leading to the gas fields along the front of the cliffs. Nine sequences and their component systems tracts can be seen in these strata. Because of the high-quality exposure and access, the Lower and Upper Sego are excellent units to study the geometry and expression of sequence boundaries and the facies contained between these regionally extensive surfaces. This paper discusses the sequence stratigraphy of the Lower and Upper Sego between Prairie Canyon on the Colorado-Utah border and Sulphur Canyon in eastern Utah. The discussion includes criteria for recognizing sequence boundaries in outcrop, the geometry of incised valleys and the nature of their fill, and the facies of the transgressive and highstand systems tracts within the sequence.

Abstract OBJECTIVE: During Day 2 of the field trip we will examine the stratigraphic architecture of the Kenilworth Member of the Blackhawk Formation and demonstrate how high-frequency cyclicity is expressed in wave-dominated shoreline deposits. Participants will be shown sedimentary facies, parasequence stacking patterns, regional truncation surfaces and lateral changes in depositional environments. Discussion will focus on how these elements are interpreted within a sequence stratigraphic framework. The Kenilworth Member is Campanian in age (Speiker, 1931; Young, 1957; 1955) and occurs near the middle of the Blackhawk Formation (Fig. 2-1). During the day we will make five stops (Fig. 2-2), beginning approximately half-way along the lateral extent of the Kenilworth exposures. The objective will be to trace the sandstones in a basinward direction, observing sequence stratigraphic and facies relationships. 0.0 Depart Green River, Utah from the parking lot of the West Winds Rodeway Inn Motel and drive west along Main St (Loop 70). Turn west on Interstate 70. 4.3 Tum north on Hwy 6/50 towards Price, Utah. The Kenilworth Member is the lowest cliff-forming sandstone succession exposed on the east side of the highway. 26.9 Pass Price River Canyon access road (Stop 3) on the right-hand side of Hwy 6/50. There is an old abandoned gas station with a blue and red sign that says “Food and Fuel” on the west side of the highway just before the access road. 49.1 - Turn east on Hwy 123 at Sunnyside Junction and drive toward the town of Sunnyside. 59.0 - STOP ONE, A:

Abstract Shallow marine strata of the Campanian Kenilworth Member, cropping out in the Book Cliffs of east-central Utah, were examined from their updip to downdip depositional limits. Thirty-one outcrop sections were measured recording facies, stratal surfaces, and paleoflow indicators. These data were used to interpret the depositional environments and to develop a chronostratigraphic framework for the Kenilworth. The geometry of stratal surfaces and the continuity of sandstones were traced between measured sections using binoculars and photographic panoramas of cliff exposures. A variety of depositional environments were identified in the Kenilworth including fluvial channels, coastal plain, foreshore, shoreface, offshore transition/offshore marine and deltaic. The vertical and lateral associations of these depositional environments indicate the presence of several parasequences separated by regionally correlative marine-flooding surfaces. Five wave-dominated shoreline parasequences were recognized, each with a north-south to northwest-southeast paleoshoreline orientation. The oldest four parasequences are stacked as a progradational parasequence set and are interpreted to be part of the highstand systems tract. A regional erosional surface overlies the highstand systems tract and east-west trending fluvial channel systems incise into the underlying shoreface deposits. The erosional surface was traced basinward where deltaic deposits occur above a coarse-grained lag. The extensive erosional surface is interpreted to be a sequence boundary which formed in response to a relative sea-level fall. The coarse-grained lag and deltaic deposits in the basin are interpreted to be part of the lowstand systems tract. A major flooding surface occurs above the lowstand and was traced updip beneath a backstepped wave-dominated shoreline parasequence of the transgressive systems tract. Sandstones of the Kenilworth Member are thus interpreted to comprise parts of two high-frequency sequences. A sequence boundary occurs within the Kenilworth and separates the highstand systems tract of an older sequence from the lowstand and transgressive systems tract of a younger sequence. The sequence boundary can be recognized by changes in parasequence stacking patterns, regionally extensive erosional truncation, and a basinward shift of facies. The magnitude of the relative sea-level fall that occurred during deposition of the Kenilworth is estimated to be at least 60 feet, based on the amount of fluvial channel incision observed at the sequence boundary. This magnitude of relative sea-level fall resulted in a basinward shift in facies of about 10 miles. The resultant paleoslope is interpreted to be 0.07 degrees, which is comparable to depositional slopes on the present day Gulf of Mexico shelf.

Abstract OBJECTIVES : The Desert and updip Castlegate provide an opportunity to study well-exposed sequences and systems tracts in nonmarine to marine settings. Because of the excellent quality of the outcrops, sequence boundaries can be traced continuously from the nonmarine, where the identification of sequence boundaries has historically been less certain, to the marine, where sequence boundaries can be well defined based on basinward shifts in facies. These outcrops also allow regional correlation of systems tracts and identification of exploration-scale facies changes within systems tracts. These stops demonstrate that sequence boundaries are regionally extensive, single physical surfaces that can be used to correlate in outcrop and the subsurface. These stops also show that strata between sequence boundaries are arranged in predictable packages and that facies within these packages commonly, but not always, have predictable characteristics. 0.0 Leave the parking lot of the Best Western River Terrace Motel in Green River, Utah. Turn right on the main road, Highway 6. 0.2 Turn left on the paved road. Drive north toward the Book Cliffs. This road parallels the Green River and is built on the Mancos Shale. 5.3 After ascending a hill which climbs on top of the Mancos out of the Green River alluvial valley, turn off of the paved road onto a gravel road that heads northeast directly toward Tuscher Canyon. 6.0 STOP ONE . Pull over to the side of the gravel road for an overview of the stratigraphy of the Desert Member of the Blackhawk Formation and the Castlegate Sandstone. This

Abstract OBJECTIVES : Today the Castlegate will be traced to the most basinward facies exposed in the Book Cliffs completing an updip to downdip analysis of the Castlegate sequence boundary and systems tracts. The Desert will be seen only at STOP ONE. As the Castlegate sequence boundary is traced basinward, changes in the sequence-boundary expression will be examined. These expressions will be compared with the expression of the sequence boundary seen yesterday. Changes in incised-valley geometry will also be studied, especially in the Horsepasture area of STOP THREE, time and weather permitting. Laramide deformation appeared to influence the Castlegate sequence boundary around the Colorado-Utah border. This influence will be examined later in the day. Leave the motel parking lot in Moab. Drive north on Highway 191. The road log begins at the bridge crossing the Colorado River outside of Moab. 0.0 Crossing the Colorado River on the north side of Moab. 2.7 Passing the entrance to Arches National Park. This park contains the greatest density of natural arches in the world from a three-foot opening to the largest, Landscape Arch. This 105-foot high ribbon of rock measures 291 feet across. Much of the faulting in the Jurassic and Triassic rocks around Moab is controlled by movement of Pennsylvanian salt, 1000's of feet thick in some places. 8.6 Pass the turnoff to Dead Horse Point. 25.0 The Mancos, Desert, and Castlegate can be seen along the Book Cliffs to the north. 29.1 Turn right onto the access road for 1-70. Drive east toward

Abstract The Desert Member of the Blackhawk Formation and the Castlegate Formation are well exposed along the Book Cliffs in eastern Utah and western Colorado. The cliffs are oriented relative to the southeasterly paleotransort direction within the Desert and Castlegate so that outcrops expose both strike and dip views of these strata] units. Starting in Tuscher Canyon outside of Green River, Utah and ending in West Salt Creek Canyon, one can traverse the Castlegate and Desert from a totally nonmarine depositional environment updip to shelf mudstones, in the case of the Desert, and red, ferruginous oolites in the case of the Castlegate downdip. Three sequence boundaries are developed in the interval, one within the Desert and and two within the Castlegate. Because of the high-quality of the exposures, the superb access to the rocks, and the orientation of the cliffs, these two units provide an unsurpassed natural laboratory to study nonmarine to marine sequence stratigraphy. Variations in sequence-boundary expression from updip to downdip, systems tract variations across a basin, changes in incised-valley geometries, and fluvial architecture in nonmarine lowstand deposits can all be analyzed in the Castlegate and Desert

Abstract OBJECTIVES : The scale of sequence recognition shifts to major first-order sequences, which may be called Sloss sequences or megasequences. The Kaskaskia-Absaroka sequence boundary is seen at STOP ONE and the Zuni-Tejas sequence boundary is seen at STOP THREE. A higher order sequence boundary within the Absaroka sequence that has been enhanced by local tectonic activity producing an angular unconformity is seen at STOP TWO. An objective today is to emphasize the effects of recurrent movement of basement faults on stratigraphy and sequence boundaries. These effects may be seen on outcrop in the San Juan Mountains, but their effects continue in a more subtle manner in the subsurface of the San Juan Basin, the site of the next two days of stops. Leaving Grand Junction, drive south to US 50 east. The road log begins at the junction of US 50 and CO 146 approximately eight miles southeast of Grand Junction. 0.0 Junction of US 50 and CO 146 near Whitewater. View of Book Cliffs to north and west, Uncompahgre uplift to west, and Grand Mesa (approximately 10,000 feet in elevation) to east, capped by Pliocene (9 Ma) lava flows. The road between here and Delta is in the lower Mancos Shale. The underlying Dakota Sandstone and Burro Canyon Formation may be seen to the west in the Gunnison River valley and close along the road in places. The rest of the Mancos Shale forms the hills to the east 31.0 Delta. Confluence of Gunnison and Uncompahgre rivers. Continue on US

Abstract The Sauk, Kaskaskia, Absaroka, Zuni, and Tejas Sloss sequences are all represented in the San Juan Mountain region, Colorado, but the Tippecanoe sequence is absent. The tectonic setting changed from cratonic bounded by a passive margin to the west during the pre-Pennsylvanian Paleozoic to active with orogenic periods related to the Gondwana collision during the Pennsylvanian and later orogenic periods related to subduction and thrusting to the west during the Mesozoic and early Cenozoic. Sedimentation also changed from thin, carbonates and mature elastics in sub-Pennsylvanian strata to thick, more immature clastics in super-Mississippian strata. Small-scale sequences are also present, but mostly await additional investigation for recognition.

Abstract OBJECTIVE : For the next two days we will examine the stratigraphy and lithofacies of Turanian- and Coniacian-age strata in northwestern New Mexico, on the lands of the Navajo Nation (see location map Figure 6-1). We will focus on the Gallup (shallow marine and coastal plain), Torrivio (predominantly braided-fluvial) and Tocito (estuarine to shallow marine) sandstone formations. An overview of the stratigraphy, lithofacies and hydrocarbon-trapping styles pertaining to these sandstones, in outcrop and from extensive subsurface well-log correlations, is presented in the accompanying paper entitled ‘High- resolution sequence stratigraphy of the Upper Cretaceous Tocito Sandstone…’. A briefer overview is also presented under STOP 1 below. The stratigraphy of the San Juan Basin is summarized in Figures 6-2, 6-3 and 6-4. These are increasingly higher resolution stratigraphic columns, with Figure 6-4, being specifically designed for this field trip. This figure reflects some of the latest ideas on the distribution of significant sequence-stratigraphic surfaces in the Late Turanian and Coniacian parts of the section. The discussion in the text at each of the field stops is designed to present two somewhat different sequence-stratigraphic interpretations of the rocks; an Exxon (Jones, Van Wagoner and Jennette) and L.S.U. (Nummedal and Riley) interpretation. The reader can draw his/her own conclusions from the observations made at outcrop and in the subsurface (see accompanying papers). Any person wishing to conduct geological investigations on the Navajo Reservation, including visiting the stops described in this guidebook, must first obtain a permit from the Navajo Nation Minerals Department, P.O. Box 146,

Abstract 0.0 Leave Holiday Inn parking lot, turn right on Broadway. 0.2 Intersection with Butler/Pinon, continue straight on Broadway. 1.7 Intersection of Main street and Broadway. Drive straight heading west on US 64. 3.4 Junction with road 170. Straight on. 11.8 Turn left on San Juan County Road 6675 to Fruitland and Four Corners Power Plant. 12.7 Intersection with San Juan County Road 6677. Go straight on 6675. 13.1 Cross the San Juan River. 15.7 Turn right on a wide dirt road which shortly becomes paved and is signposted for Da Na Has Ta (Full Gospel Church). Now heading west. 16.1 The road becomes paved. 16.8 Pass a sign reading Da Na Has Ta. 17.4 Pass water tower on left. Four Corners Power Plant clearly visible to the left (south). The Hogback is straight ahead. 21.5 The road crosses through the Cliff House Sandstone cropping out along the Hogback. Ship Rock can be seen in the distance to the left. 23.2 Pass a dirt road to the right. There are pump jacks on either side of the road. These pump jacks are part of the Hogback oil field producing from the Dakota Sandstone at relatively shallow depth and the much deeper Pennsylvanian Hermosa Group. 24.2 Crossing the bridge over Chaco River. 24.6 Turn left across cattleguard on to dirt road. The road forks, take the left fork. 25.1 Road splits. Continue straight ahead on main dirt road. Ahead is a good view of the Hogback. 25.2 Reach a four-way intersection. Proceed

Abstract In the subsurface of the San Juan Basin, New Mexico, the Coniacian Tocito Sandstone is composed of four sequences (Tocito-1, Tocito-2, Tocito-3 and Tocito-4). Over their extent, each basal sequence boundary is marked by erosion and truncation of underlying strata and onlap by shallower water, typically estuarine strata. Axes of erosion are typically narrow, straight to slightly sinuous and locally join to form tributary-like junctures. These patterns are interpreted to be incised valleys cut by fluvial and estuarine systems during lowstands in relative sea level. The four sequences stack in a backstepping pattern to form a retrogradational sequence set. Toward the outcrop belt (southwest), the sequence boundaries merge to form a composite surface which everywhere separates Tocito strata from underlying Gallup strata. Sandstone accumulations occur along sinuous lows associated with incised sequence boundaries. Two end-member types of lowstand facies exist: an open-marine facies dominated by marine mudstone with minor thin-bedded and bioturbated sandstone beds and a sand-prone, tidally influenced facies consisting of beds of medium to coarse grained, highly glauconitic sandstone. Tidal indicators include double clay drapes, flaser and lenticular bedding and large- to small-scale sigmoidal and trough cross bedding. Iron-cemented shale rip-up clasts, quartz and phosphatic pebbles, sharks teeth, Inoceramus and oyster shell fragments also characterize the Tocito Sandstone. Ichnofauna are dominated by Thalassinoides, Paleophycus and Planolites burrows with locally abundant robust Ophiomorpha burrows. Bedding and ichnofauna indicate sand deposition within estuaries. Reactivated basement-involved faults were the dominant influence on Tocito drainage patterns. These northwest-trending basement-involved faults, which were active episodically throughout the Phanerozoic, created linear pathways that acted as catchments for southeast-directed stream and estuarine systems. Reactivation of these structures during the Tocito lowstands led to a reorientation of regional sediment transport directions nearly perpendicular to that of the underlying Gallup shoreline deposits. The close vertical juxtaposition of erosional sequence boundaries and variably filled incised valleys created abundant stratigraphic traps. Most hydrocarbon traps are dependent on a combination of trapping elements which can include a bend in the valley axis (lateral-trapping clement), valley edges where valley-fill sandstones thin to zero (lateral and updip seals), and truncation of sandstone valley-fill by younger, shale-filled valleys (lateral, updip and top seals). Through time, valleys tend to become broader and shallower and are filled with strata that are more shale-prone and more open marine in character. Hydrocarbon production is chiefly from the older, sand-prone valley systems. Previous workers viewed the composite erosional surface at the base of the Tocito sequences as a single erosional unconformity which was progressively onlapped through time by beaches, offshore bars and shelf-sand ridges. In these models, hydrocarbon-trapping mechanisms relied on gradual facies changes of the sandy bars into marine shale. The incised-valley model accounts for the lidal and estuarine indicators, complex erosional patterns and hydrocarbon-trapping styles of the Tocito Sandstone.

Abstract The objective of this field research conference is to address basic issues in shallow marine sequence stratigraphy. One central issue is the origin of the many discontinuities (unconformities and diastems) we observe: Three possible mechanisms may produce such discontinuities: (1) eustatic sea level fall, (2) tectonic uplift or tilting of the basin, and (3) lateral shifts in depositional environments (the origin of most diastems). Late Turonian and Coniacian rocks of the western San Juan Basin provide an excellent section of rocks in which to address these questions, because we believe that the three major discontinuities present within this part of the stratigraphic column are examples of all these listed modes of origin. The analysis of the origin of these unconformities is based on: (1) a synthesis of relevant biostratigraphic data (including much not previously published) in order to constrain their ages with the highest possible precision, (2) documentation of parasequence stacking patterns and depositional systems to relate unconformities to their correlative deposits, and (3) subsurface data that demonstrate local tectonic movement.