ABSTRACT We present here a comprehensive record of Miocene terrestrial ecosystems from exposures of the Monterey Formation along the Naples coastal bluffs, west of Santa Barbara, California. Constrained by an updated chronology, pollen analyses of 28 samples deposited between 18 and 6 Ma reflect the demise of mesophytic taxa that grew in a warm, wet environment during the late early and early middle Miocene and the development of a summer-dry/winter-wet Mediterranean climate during the late Miocene. Broadleaf tree pollen from mesophytic woodlands and forests now found in the southeastern United States and China ( Liquidambar , Tilia , Ulmus , Carya ) characterized the Miocene climatic optimum (16.9–14.7 Ma), the middle Miocene climate transition (14.7–13.8 Ma), and the interval up to ca. 13.0 Ma. Subsequently, during the late middle to early late Miocene, between 13.3 and 9.0 Ma, oak woodlands and herbs (Asteraceae, Amaranthaceae, Poaceae) from beach scrub and chaparral increased as ocean temperatures cooled and the climate became drier. Between ca. 8.9 and 7.6 Ma, pine increased mostly at the expense of oak ( Quercus ) and herbs, suggesting a period of increasing precipitation. During the latest Miocene (7.5–6.0 Ma), an increase of herb-dominated ecosystems (chaparral, coastal scrub) at the expense of pine reflects the full development of a summer-dry/winter-wet climate in coastal southern California.

ABSTRACT The Monterey Formation, consisting of siliceous and calcareous biogenic sediments, was deposited during the transition from a relatively warm greenhouse climate in the early Miocene to the cooler temperatures of icehouse climatic conditions during the early middle to late Miocene. This cooling event was associated with global paleoclimatic and oceanic changes assumed to be related to the deposition of organic carbon–rich sediments into the marginal basins of California. This chapter introduces an age model for the Miocene strata at Naples Beach based on a composite stratigraphic section and standardized data set, providing the framework for the integration of biostratigraphic zones with a series of astronomically tuned siliceous and calcareous microfossil bioevents, an updated strontium isotope stratigraphy, new tephrochronology ages, and ages from specific magnetostratigraphic units. This multidisciplinary approach, utilizing the integration of microfossil disciplines with independent age controls, is critical to obtaining an age resolution of ~200 k.y. for the majority of the Monterey Formation section. This chronostratigraphic framework improves the age control of the boundaries between the California benthic foraminiferal stages and provides more age refinement for the possible hiatus and condensed interval within the Carbonaceous Marl member of the Monterey Formation. The recalibrated ages for the tops of the Miocene benthic foraminiferal stages are Saucesian (ca. 17.4 Ma), Relizian (15.9 Ma), Luisian (13.1 Ma), and Mohnian (7.7 Ma). Also, the time missing in the hiatus between the Luisian and Mohnian is <200 k.y., and the duration of the condensed interval is from 13.0 to 11 Ma. This refined age model provides a correlation of the organic carbon–rich intervals occurring in the Luisian and lower Mohnian stages within the Naples Beach strata to the deep-sea δ 13 C maxima events CM5 (ca. 14.7 Ma) and CM6 (ca. 13.6 Ma), suggesting episodic increases in organic carbon deposition along the continental margins coincided with the Miocene carbon isotope excursion found in deep-sea cores. The transition from the Miocene climatic optimum to the icehouse world consisted of four climatic and oceanic phases (from ca. 17.5 to ca. 7 Ma), which are represented in the onshore section by variations in the organic carbon and phosphate contents, the occurrence of calcareous and siliceous lithologic facies, and the distribution of microfossils, especially changes in the benthic foraminiferal assemblages.

Abstract Assessment of undiscovered oil and gas resources is based on geological elements and processes of a petroleum system. Application of the petroleum system in the oil industry varies largely on how the processes of hydrocarbon generation, migration, and entrapment are described. It is often depicted as a relationship between source and reservoir rocks connected by fluid paths ( e.g ., carrier beds, faults, etc .) through geological time. When appropriate conditions (time, temperature, and trap formation) are reached, the effort is focused on secondary migration from source to reservoir. Secondary migration efficiency is a function of the distance between source and reservoir rocks. Tertiary migration (or ‘dismigration’) refers to fluid movement from reservoir to reservoir and involves migration pathways (fault or sand beds and/or unconformities). There has been much research on source rock quality and its relationship to hydrocarbon potential. Much less has been documented about the rate, mechanisms, and pathways by which gases migrate through kilometer-scale sequences of fine-grained sediments. Mass balance calculations supported by laboratory experiments on good quality source rocks show that significant volumes of hydrocarbons can be generated and expelled from the source rock, but exploration results show that only a small fraction (<10%) is trapped within conventional reservoirs. Dispersion in the carrier beds (10 to 20%), retention in the source rock (30 to 40 %), ‘dismigration’ (10 to 20%), and biodegradation (10 to 20%) are commonly assumed to be the altering mechanisms of the bulk fluid generation. The proximity of source rock and reservoir rock becomes critical to fluid preservation and accumulation. The unconventional Barnett Shale and Cotton Valley tight sands of East Texas are no different from other petroleum systems. The Barnett Shale is a classic shale gas system that includes the elements of source, reservoir, and seal. The Cotton Valley Formation exhibits an inter-fingering shale/sand system that juxtaposes source and reservoir, offering preservation and high migration efficiency. Occurrences of sweet spots in Barnett Shale are related to the original source rock richness, maturity, and confinement of the source beds. The Fort Worth basin of East Texas is asymmetric and has a polyphased burial history. Its western part along the Washita high has undergone uplift and erosion at the Miocene. The resulting liable asphaltenes precipitation has created a permeability barrier within the shale preventing gas from escaping laterally to the west. The lower Barnett encased between the Marble Falls Limestone and the Chappel Limestone has limited gas leakage to the top and the bottom, creating an optimum seal for the Newark Field where the highest gas production per well has been observed. Laminated carbonates and chemically induced carbonate nodule deposits in the early organic diagenesis provide vertical and lateral baffles to fluid flow thus enhance the confinement within the most productive Barnett Shale. In the Cotton Valley Formation, significant permeability reduction occurs within the interfingering shale and tight sands. The migration of oil from shale to sand has accumulated a significant volume of oil that ultimately has cracked to gas when burial reached the gas window in the Cotton Valley. This secondary cracking has resulted in high pressures extending far beyond the source rock, flushing the interstitial water to overlaying formations. Different chemical water mixes has lead to mineralization and thus diagenetic seals enhancing confinement, which has result in stair-step pressure offsets occurring independently of lithology profiles.