FIELD TRIP #1

"Upper Pennsylvanian Carbonates to Terrigenous Clastics Transitions: An Eastern Shelf Example"

(Friday/Saturday) *Cost $60/person (Students $25) 20-person maximum

Leaders: William D. Pollard David S. Ball

Outcrops of the Upper Pennsylvanian Canyon Group (Missourian) in the Brazos River Drainage of North-Central Texas provide a good opportunity to observe thick limestones that are stratigraphically equivalent to major oil and gas reservoirs in the Midland, Delaware, and other Mid-Continent and Rocky Mountain Basins. The reservoirs of many such fields have been variously described as parts of "atolls", "banks" and "reefs" that had significant positive depositional topography. Winchell Formation outcrops in the Possum Kingdom Lake area have been called "algal bank" and "neritic bank limestone." In addition to connotations of depositional relief, the presence of abundant remains of leaf like or "phylloid" algae has been considered causal to bank or mound formation as well as abundant primary shelter porosity, ideal situations for both trap and reservoir formation. Phylloid algae are abundant in the outcrops to be visited and discussed.

On Friday evening, a brief introduction to the regional geology and field trip setting will be provided and participants will have the opportunity to examine polished rock slabs with binocular microscope and hand lens. After dinner, a slide show on the possible significance of phylloid algae in carbonate sedimentation will be provided.

Saturday's field trip will start in the area of thickest Winchell Limestone outcrops on the Possum Kingdom lakefront. A boat traverse will allow examination of continuous lateral exposures and examples of bank of mound-like depositional topography. Lithologies of laterally persistent beds, mounds, and mound-flank beds will be illustrated with photomicrographs, acetate peels, and slab photographs. Back onshore, participants will have "hands-on" encounters with a variety of outcrops, including tidal channel fill in delta-plain and shore face sediments of the Wolf Mountain Shale, open shelf, mound and mound-flank lithologies of the Winchell Limestone. A discussion of porosity evolution in phylloid algal limestone will be provided.

For this shortened trip, what is normally a three-mile traverse into Loving Creek Drainage will be covered with a poster presentation, demonstrating the nature of the lateral transition of thick Winchell Limestones to laterally equivalent terrigenous clastics of the Wolf Mountain Shale, both at the surface and in the nearby subsurface. The remainder of the day will be devoted to a series of short stops to observe deltaic sandstone sequences in the Wolf Mountain Shale and Winchell Limestones in facies transition. The last stop is great for collecting marine invertebrate fossils.

Logistics: Field trip commences at 4 pm (Friday) in Graham (Gateway Inn) and ends Saturday at 4:30 pm. Contact Lee Peterson for additional information on hotel/transportation (817 870-9799 lee@palopintoexploration.com) *Cost excludes hotel ($44 + tax), Fri. dinner, and Sat. breakfast.

FIELD TRIP #2

"PENNSYLVANIAN ADVENTURES IN PALO PINTO COUNTY"

Sedimentology and Structure of Terrestrial to Shallow Marine Outcrop Reservoir Analogs, Pennsylvanian Mingus Formation, Mineral Wells, Texas

(Saturday) Cost $75/person (Students $25) 30 people maximum, 15 minimum

Janok P. Bhattacharya1, Karen D. McLinjoy(1), and Russel Davies(2)
(1:University of Texas @ Dallas Geosciences Department, Richardson, Texas. 2:Rock Deformation Research, USA Inc., McKinney, Texas.)

Pennsylvanian shelf and non-marine clastic depositional systems are well exposed in several cliff sections around Mineral Wells, Texas. We will examine the entire spectrum of terrestrial to shelf clastic environments, including gravelly fluvial deposits at Mineral Wells State Park, an incised valley deposit in the town of Mineral Wells and wave-dominated shore-face deposits near Wizard Wells. Much of the focus of the trip will be on spectacular examples of normal and growth faulted strata within fluvial-dominated delta front sandstones near Bennett, Texas. These are potentially analogous to the more regional-scale growth faults that are big producers in the Gulf Coast. These faults can also introduce significant heterogeneity in subsurface analogs and we will discuss the effective properties of the faults as conduits and seals. Several stops are excellent locales for collecting fossil plants and marine invertebrates.

Logistics: Cost is inclusive of transportation and lunch. Trip will depart from Radisson Hotel at 8 am, returning at 5 pm. Contact Tom Brace for additional information (817 870-2601 tbrace@rangeresources.com)

FIELD TRIP #3

"SHALLOW MARINE DEPOSITIONAL ENVIRONMENTS"

Depositional Environment of the Woodbine Sandstone, Lewisville Member, In Outcrop at Lake Grapevine, Tarrant County, Texas

(Wednesday) Cost $150/person (25 people maximum, 15 minimum) RESPONSE REQUESTED BY JANUARY 15

Instructors: Bo Henk, Pacheron Group, McKinney, TX, Adjunct Assist. Professor of Geology, TCU, and John A. Breyer, Prof. of Geology, TCU.

This is a one-day field trip designed to show participants the variety of depositional environments within the Lewisville Member of the Woodbine Formation along the shores of scenic Lake Grapevine immediately north of the Dallas-Fort Worth Airport. We will examine the stratigraphy and sedimentary structures of the sandstones, with an emphasis on trace fossils. The sediments were deposited in a classic barrier-island system, with tidal inlets, flood tidal deltas and marsh deposits. The geology seen in outcrop can be applied in the subsurface both by exploration and production geologists and by engineers and geophysicists.

We will examine sandstones with an enormous variety of sedimentary structures, including wave ripples, trough cross stratification, interference ripples, and storm-generated stratification (HCS). Trace fossils in the sandstones include Ophiomorpha, Rhyzocorallim, Rosselia, Thaslassinoides, Palaeophycus, museum-quality sea-urchin traces (Conichnus) with the imprints of the tentacles still preserved (!) and lobster resting traces (Rusophycus). We will also examine a unique rock type associated with a fiddler crab colony indicative of a backshore wash-over fan setting. If lake levels are low enough we may have the opportunity to see some dinosaur tracks. Lateral and vertical variations in facies are shown in a specially constructed photo-mosaic of outcrops along the shoreline. The photo-mosaic and a cross-section based on twenty closely-spaced measured sections provide the basis for discussing reservoir continuity and heterogeneity.

Logistics: Depart the Radisson Hotel at 8 am. Transportation and lunches will be provided. A CD ROM with all of the outcrop photos and measured sections will be given to participants. Field Trip will end at 4:00 pm and return to Radisson at 4:30 pm. Contact Andrée French-Griffin for additional information (817 335-2222 agriffin@wagneroil.com)