Major Transgressive-regressive Cycles Research Articles

Cyclic Deposition and Sea Level Changes: Record in Twin Creek Limestone (Jurassic), Northern Utah: ABSTRACT

The Twin Creek Limestone in northern Utah was deposited in a shallow sea during the Middle Jurassic. Paleocurrent patterns determined from study of ripple marks and cross-stratification, and the distribution of facies, indicate that the average shoreline orientation was northeast-southwest. Two major transgressive-regressive cycles, which are correlated with sea level curves proposed by P. R. Vail and others for the Jurassic, are delineated. The lower cycle in the Twin Creek Limestone unconformably overlies the Lower Jurassic Nugget Sandstone. The Twin Creek Limestone is represented by deposits of the Gypsum Springs, Sliderock, Rich, and Boundary Ridge Members. Lithofacies in this cycle sequence grade upward from reworked Nugget Sandstone at the base into oosparite, micrite, and silty ripple-marked micrite, to an overlying discontinuous red siltstone unit. The cycle is correlative with the J2.1 global cycle of relative change of sea level. The upper cycle is separated from the lower one by a hiatus of unknown duration. This boundary is recognized on the basis of the thin discontinuous red bed at the top of the Boundary Ridge Member. The cycle consists of the Watton Canyon, Leeds Creek, and Giraffe Creek Members. Lithofacies grade from oosparite at the base up into micrite, silty micrite interbedded with sandy oosparite, and sandstone. The upper boundary is marked by the base of the Middle Jurassic Preuss Sandstone. The cycle is correlative with the J2.2 global cycle. Duration of these global cycles is about 8-10 m.y. Recognition of the cycles leads to improvement in stratigraphic and structural interpretation incorporating the effects of sea level changes. End_of_Article - Last_Page 941------------

Paleoenvironments of Late Albian Stage (Early Cretaceous) of Eastern Trans-Pecos, Texas: ABSTRACT

Upper Albian rocks in eastern Trans-Pecos Texas consist of a depositional sequence that records a major transgressive-regressive cycle, beginning with an initial transgression of the early late Albian seas over a regionally disconformable surface and ending with the onset of late Albian regression. The history of these events is recorded in rocks of the Fort Lancaster Formation and its western equivalent, the Boracho Limestone. These rocks were deposited in several depositional systems that developed on the Comanche shelf and an associated shelf basin called the Fort Stockton embayment. These depositional systems include the carbonate-shelf system, the shelf-basin system, and the carbonate-shoal system. Each system is recognized by unique suites of lithofacies, differentiated on the basis of petrographic and outcrop characteristics: skeletal wackestone, interbedded shale and wackestone, oyster packstone/shale, skeletal grainstone, and calcareous shale. Associated with these lithofacies are the following biofacies: Protocardia-Macraster, Globigerina, Nuculana-Syncyclonema, Texigr phaea, Lopha, and Miliolina. Within a biostratigraphic framework based on ammonite zones, the geographic and stratigraphic distribution of a depositional systems and their associated lithofacies and biofacies indicate that late Albian deposition primarily was influenced by periodic terrigenous influxes from the northwest over the Comanche shelf. This was coupled with tectonically controlled subsidence in the Fort Stockton embayment. The depositional sequence culminated in the development of widespread carbonate sand shoals prior to the onset of emergence. End_of_Article - Last_Page 461------------

Facies and Depositional Tectonics of Middle Jurassic Carmel Formation, Southern Utah: ABSTRACT

The Middle Jurassic Carmel Formation of southern Utah is divided into two informal members deposited during a major transgressive-regressive cycle. The relatively thin lower member was deposited in a shallow, subtidal, marine to coastal, sabkha environment that advanced southeastward, onlapping and reworking coastal dunes of the Navajo and Page sandstones. Lithofacies of the lower Carmel include calcareous mudstone, bivalve micrite, oolitic grainstone and packstone, ostracod pelletal micrite, dolomicrite, algal stromatolites, aphanitic dolomite, and minor nodular gypsum and sandstone. The sporadic northwest retreat of the Carmel Sea and progradation of coastal sabkha and continental sabkha and dune sediments is recorded in the thick upper member of the Carmel. Lithofacies include algal stromatolites, aphanitic dolomite, calcareous mudstone, nodular gypsum, horizontal to gnarly-bedded sandstone, and cross-bedded sandstone. The lower Carmel undergoes rapid west to east thinning and facies changes, indicating that during the early Middle Jurassic (late Bajocian) the Hurricane fault was a tectonic hinge line that separated a westward tilting unstable shelf slope to the west from an unstable shelf to the east. Furthermore, lower Carmel facies, isopach anomalies, and regional stratigraphic and structural correlations indicate that anomalous subsidence and sedimentation in the present Sevier-Paunsagunt fault zone were contemporaneous and genetically related to initial deformation of the Middle Jurassic San Pete-Sevier rift of the hinge-line region of central Utah. End_of_Article - Last_Page 712------------

Smackover Formation of Gulf Coast Region: ABSTRACT

The Smackover Formation in the United States Gulf Coast region has been the target of continuing, and indeed renewed, exploratory interest of the oil industry. It is important that geologists understand the depositional and diagenetic realms that affected the Smackover, because of the influence they have on reservoir development. The Smackover was deposited during a major transgressive-regressive cycle. High-energy fossiliferous, pelletal, and oolitic grainstones deposited during the regressive End_Page 534------------------------------ phase form carbonate reservoirs that are widespread in Texas, Arkansas, Louisiana, Mississippi, Alabama, and Florida. Although much of the upper Smackover displays packstone and grainstone textures, there are variations in the type of allochems, percentage of micrite, and clastic sand content. For example, there are oolitic grainstones in the upper Smackover of east Texas, Arkansas, Louisiana, and southeastern Mississippi; micritic, pellet packstones are most common in parts of Alabama and the Florida panhandle; and deltaic, beach, and offshore-bar clastic sands are intermixed with carbonate beds in much of Mississippi. Of greater significance to the exploration geologist are variations in the amount and type of porosity within similar Smackover lithologies. These variations result from differences in diagenetic regimes. In Arkansas, Louisiana, and eastern Mississippi, the best reservoirs display incompletely cemented primary porosity. The preservation of porosity may be the result of early freshwater cementation, which occurred in areas that were uplifted and exposed during salt movement. Most of the updip Smackover carbonate grainstones contain leached moldic porosity, developed as extensive freshwater flushing occurred near the regional shoreline. Combinations of dolomitized intercrystalline and leached moldic porosity are prevalent in east Texas and Alabama-Florida. Dolomite porosity is less depe dent on early salt tectonics, although salt structures may still affect the shape of the productive reservoir. End_of_Article - Last_Page 535------------

Upper Cretaceous Subsurface Stratigraphy of Atlantic Coastal Plain of New Jersey

Foraminiferal biostratigraphic data indicate that the stratigraphic history of the Upper Cretaceous rocks of the coastal plain of New Jersey can be considered in terms of four main depositional phases which in turn reflect major transgressive-regressive cycles. The first depositional phase can be seen against the backdrop of the well-known Cenomanian eustatic rise of sea level. A new stratigraphic unit, the Bass River Formation, is proposed for the calcareous clayey silts deposited during this initial encroachment of the sea into the region. The Bass River Formation ranges in age from earliest Cenomanian (Washitan) to early Turonian (Eaglefordian), and contains the following planktonic foraminiferal zones: Rotalipora greenhornensis/Praeglobotruncana delrioensis Zone, Rotalipora cushmani Zone, and Marginotruncana helvetica Zone. Its age equivalents in outcrop are the upper Patapsco and Raritan Formations. The Bass River is restricted to the subsurface with only a marginal-marine facies in the Woodbridge Clay Member of the Raritan. This transg ession apparently reached its climax in the early Turonian during which the Woodbridge Clay Member was deposited. Phase two marks the only major regression in the coastal plain. The Sayreville Sand Member and the South Amboy Fire Clay Member of the Raritan were deposited during this phase which also is represented by a probable hiatus in which part of the Coniacian is missing. Toward the center of the Salisbury embayment continuous marine sedimentation took place. During phase three another widespread marine transgression occurred in which the Merchantville and Magothy Formations were laid down. This transgression established the strandline for the deposition of subsequent Cretaceous units. The Woodbury Clay is the shoal facies which marked the end of this phase. The Merchantville in the subsurface contains the following early Santonian to early Campanian planktonic zones: Marginotruncana concavata Zone, Globotruncana fornicata Zone, and Archaeoglobigerina blowi Zone. The Woodbury contains part of the A. blowi Zone and the Ventilabrella glabrata Zone. Finally, the oscillation of the shoreline during the late Campanian and Maestrichtian produced the familiar alternation of greensands (Marshalltown, Navesink, and basal Hornerstown), with regressive sand units (Englishtown, Wenonah-Mount Laurel, and Redbank-Tinton).