Abstract Today’s trip introduces Field Forum participants to the earliest stages of magmatism in the Cretaceous section of the Sierran arc. Despite the paucity of fresh rock exposed in the western foothills, we have determined that the Fine Gold Intrusive Suite is a massive (>3100 km 2 ) and long-lived (ca. 19 million years, Lackey et al., 2012) intrusive complex, preserving a record of magmatism that provides considerable insight into the evolution of arc magma systems intruding across major crustal terrane boundaries. The primary units of the Fine Gold Intrusive Suite that will be viewed during the field excursion include the Bass Lake Tonalite, Ward Mountain Trondhjemite, and Knowles Granodiorite ( Fig. 2-1 ). The low-K 2 O, 87Sr/86Sr, high-Sr/Y, high- ?18O, and peraluminous composition of the Fine Gold Intrusive Suite rocks are geochemically distinct from the younger rocks of the central and eastern Sierra (Fig. 2-2 )…

Abstract Since its discovery in 1993, the mid-Irvingtonian (0.78–.55 Ma) Fairmead Landfill locality has produced thousands of specimens representing 72 taxa (2 fish, 2 amphibians, 3 reptiles, 6 birds, 29 mammals, 1 bivalve, 1 gastropod, 12 plants/palynomorphs, and 16 diatoms). Fossils occur in sediments representing distal alluvial fan channel, distal fan overbank flood or sheetflood, and marsh/lacustrine deposits of the upper unit of the Turlock Lake Formation. A broad range of taphonomic conditions is represented. Overall, the biota suggests a predominantly grassland habitat. The field trip will make three stops, the Madera County Paleontology Collection repository in downtown Madera, California; the Madera County Fairmead Landfill site; and the Fossil Discovery Center of Madera County.

ABSTRACT The stratigraphy of the Cretaceous section of the Northern San Joaquin basin is composed of deep and shallow marine, detrital elastics, lagoonal, and delta facies. The sands are massive in the delta front with thin shales and small amounts of lignite. Westward in the deeper neritic zone an intermediate sand/shale sequence develops from longshore transport and basinward dispersal of the clastic sediments. In the deeper bathyal and abyssal environments the prodelta shales merge with deep water turbidite sand. Four depositional systems have been recognized in the study area: 1) Eastern fluvial system, 2) An eastern deltaic system, 3) Central shelf-slope system, and 4) Submarine canyon and fan system. With the uplift of the ancestral Sierra Nevada Mountains, compressional forces caused reverse faulting of the subjacent metasediment series and late Cretaceous sediments. These tectonic forces lead to northwest-southeast trends of anticlinal type structures that are prevalent in Gill Ranch Gas, Moffat Ranch Gas, and Chowchilla Gas fields. These faulted anticlines, or paleo highs created the “shelf-slope” environment at the western edge of the productive trend. The Starkey sands are suggested to be delta front sands deposited along the edge of the shelf/slope system. The Lathrop, Winters, and Tracy sands are considered to be deep marine turbidite deposits sourced from the cyclic western migrating Starkey delta. The Blewett sands of the Moreno Formation are submarine turbidite sands deposited in a regressive cycle of sedimentation in conjunction with the deposition of the Moreno shale member.

ABSTRACT One of the more active exploration areas of California for the past seven years has been the Blewett trend of the Northern San Joaquin Valley. This deep water sand trend extends from Gill Ranch Gas Field to Vernalis Gas Field, over sixty miles in length. Recent exploration activity has been focused in the southern third of the trend where significant reserves of gas have been developed in the upper Cretaceous Blewett Formation, west of Gill Ranch, Moffat Ranch and Chowchilla Gas Fields. UNOCAL initiated the interest with the O’Banion #1, located in section 25, Tl 1S/R13E, MDB&M. The well was drilled in July, 1989, and encountered approximately 80’ of gross gas sand in the top of the Blewett Formation, at a depth of 6520’ KB. The Merrill Avenue discovery confirmed the geophysical interpretation of a seismic anomaly identified on several seismic lines. The gas appears to be trapped on a low relief anticlinal closure. Additional drilling to develop the field however, met with limited success. First production began on October 1991, after the construction of a 30 mile pipeline. McFarland Energy and partners obtained a significant acreage position north of the discovery. McFarland drilled the Wolfson #1-10, in March of 1992, about 3 miles northwest of UNOCAL’s O’Banion #1. The well encountered 54’ gross Blewett gas sand on water. Additional drilling, based on identification of geophysical anomalies in the Blewett met with a high degree of success in the Merrill Avenue, Mint Road, and Ash Slough gas fields. Production data from all recent wells indicates most wells to have recoveries from 0.5-1.0 BCFG. A few wells have produced greater than 1.0 BCFG, and only the O’Banion #1 has produced in excess of 10.0 BCFG.