Southeast Georgia Embayment Research Articles

Quantitative Evaluation of CO2 Storage Potential in the Offshore Atlantic Lower Cretaceous Strata, Southeastern United States

The geological storage of CO2 in the Earth’s subsurface has the potential to significantly offset greenhouse gas emissions for safe, economical, and acceptable public use. Due to legal advantages and vast resource capacity, offshore CO2 storage provides an attractive alternative to onshore options. Although offshore Lower Cretaceous reservoirs have a vast expected storage capacity, there is a limited quantitative assessment of the offshore storage resource in the southeastern United States. This work is part of the Southeast Offshore Storage Resource Assessment (SOSRA) project, which presents a high-quality potential geological repository for CO2 in the Mid- and South Atlantic Planning Areas. This is the first comprehensive investigation and quantitative assessment of CO2 storage potential for the Lower Cretaceous section of the outer continental shelf that includes the Southeast Georgia Embayment and most of the Blake Plateau. An interpretation of 200,000 km of legacy industrial 2D seismic reflection profiles and geophysical well logs (i.e., TRANSCO 1005-1-1, COST GE-1, and EXXON 564-1) were utilized to create structure and thickness maps for the potential reservoirs and seals. We identified and assessed three target reservoirs isolated by seals based on their effective porosity values. The CO2 storage capacity of these reservoirs was theoretically calculated using the DOE-NETL equation for saline formations. The prospective storage resources are estimated between 450 and 4700 Mt of CO2, with an offshore geological efficiency factor of dolomite between 2% and 3.6% at the formation scale.

The Brunswick magnetic anomaly: Geophysical signature and geologic source

Research Article| February 28, 2019 The Brunswick magnetic anomaly: Geophysical signature and geologic source Patrick D. Duff; Patrick D. Duff 1School of Earth, Ocean, and Environment, University of South Carolina, Columbia, South Carolina 29208, USA Search for other works by this author on: GSW Google Scholar James N. Kellogg James N. Kellogg 1School of Earth, Ocean, and Environment, University of South Carolina, Columbia, South Carolina 29208, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Patrick D. Duff 1School of Earth, Ocean, and Environment, University of South Carolina, Columbia, South Carolina 29208, USA James N. Kellogg 1School of Earth, Ocean, and Environment, University of South Carolina, Columbia, South Carolina 29208, USA Publisher: Geological Society of America Received: 08 Aug 2018 Revision Received: 27 Jan 2019 Accepted: 29 Jan 2019 First Online: 28 Feb 2019 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2019 Geological Society of America Geology (2019) 47 (4): 355–358. https://doi.org/10.1130/G45462.1 Article history Received: 08 Aug 2018 Revision Received: 27 Jan 2019 Accepted: 29 Jan 2019 First Online: 28 Feb 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Patrick D. Duff, James N. Kellogg; The Brunswick magnetic anomaly: Geophysical signature and geologic source. Geology 2019;; 47 (4): 355–358. doi: https://doi.org/10.1130/G45462.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We used integrated analyses and forward and inverse modeling of potential field data to interpret the enigmatic Brunswick magnetic anomaly (BMA), a prominent negative magnetic lineation that is developed within the ocean-continent transition of the Southeast Georgia Embayment. From magnetic profiles extracted from gridded data, residual magnetic maps, and simultaneous 2.5-dimensional forward and 3-dimensional Euler inverse modeling of the gravity and magnetic fields, we suggest that the source of the BMA is a series of semicontinuous to discrete, late-stage rift-related mafic intrusions of Mesozoic age. This interpretation is supported by the observation that the BMA is independent of the East Coast magnetic anomaly, implying a predrift source, and that the amplitude and frequency of the anomaly change nearshore across a fracture zone that divides the offshore BMA, where continental breakup occurred, from the onshore BMA. Modeling demonstrates for the first time that a Mesozoic rift-related mafic body can explain the anomaly onshore. The lack of a BMA equivalent on the West African margin may indicate that Atlantic rifting began with a single lithospheric dislocation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Lithology-based sequence-stratigraphic framework of a mixed carbonate-siliciclastic succession, Lower Cretaceous, Atlantic coastal plain

This study presents a lithology-based sequence-stratigraphic framework and depositional model for Lower Cretaceous, mixed siliciclastic-carbonate sediments of the Mid-Atlantic coastal plain (eastern United States). Lithologic data from cores and cuttings were integrated with wireline logs and two-dimensional seismic data to document lithofacies variability and stacking patterns across the Albemarle Basin of eastern North Carolina. Ten facies associations are defined, which are variably present within siliciclastic- and carbonate-dominated depositional profiles interpreted to extend from onshore lowland coastal plain to deep-shelf depositional environments. Three depositional sequences (0, 1, 2) were identified, each with component upward-shoaling parasequences. Seismic reflectors typically coincided with key sequence-stratigraphic surfaces, which guided correlations between wells. Parasequences are grouped into parasequence sets with progressive progradational or retrogradational (highstand and transgressive systems tracts, respectively) stacking patterns. Transgressive parasequences are thinner, uniform in thickness, and tend to be more dominated by molluskan carbonate facies. Highstand parasequences have more variable thickness, are siliciclastic dominated, and tend to be progradational on seismic data. Late highstand deposits of sequence 1 are dominated by restricted carbonate facies that likely reflect increased aridity. Lowstand deposits were not recognized from onshore well and seismic data. The sequence-stratigraphic framework developed documents the complex spatial and temporal facies relationships within a wave-dominated, mixed carbonate-siliciclastic passive-margin succession. The strata studied document the complex interplay of lithofacies within a transition zone between near-shore carbonate-dominated strata to the south (Southeast Georgia Embayment) and siliciclastic-dominated marginal-marine successions to the north (Baltimore Canyon Trough). It also provides a useful stratigraphic calibration set for coeval offshore sediments that have been identified as potential areas for hydrocarbon exploration.

Structural and tectonic setting of the Charleston, South Carolina, region: Evidence from the Tertiary stratigraphic record

Eleven upper Eocene through Pliocene stratigraphic units occur in the subsurface of the region surrounding Charleston, South Carolina. These units contain a wealth of information concerning the long- term tectonic and structural setting of that area. These stratigraphic units have a mosaic pattern of distribution, rather than a simple layered pattern, because deposition, erosion, and tectonic warping have interacted in a complex manner through time. By generating separate structure-contour maps for the base of each stratigraphic unit, an estimate of the original basal surface of each unit can be reconstructed over wide areas. Changes in sea level over geologic time generate patterns of deposition and erosion that are geographically unique for the time of each transgression. Such patterns fail to persist when compared sequentially over time. In some areas, however, there has been persistent, repetitive net downward or upward movement over the past 34 m.y. These repetitive patterns of persistent motion are most readily attributable to tectonism. The spatial pattern of these high and low areas is complex, but it appears to correlate well with known tectonic features of the region. This correlation suggests that the tectonic setting of the Charleston region is controlled by scissors- like compression on a crustal block located between the north-trending Adams Run fault and the northwest-trending Charleston fault. Tectonism is localized in the Charleston region because it lies within a discrete hinge zone that accommodates structural movement between the Cape Fear arch and the Southeast Georgia embayment.

Stratigraphic and palaeoenvironmental summary of the south-east Georgia embayment: a correlation of exploratory wells

A Continental Offshore Stratigraphic Test (COST) well and six exploratory wells have been drilled in the south-east Georgia embayment. The oldest rocks penetrated are weakly metamorphosed Lower Ordovician quartz arenites and Silurian shales and argillites in the Transco 1005-1 well and Upper Devonian argillites in the COST GE-1 well. These marine strata, which are equivalent to the Tippecanoe sequence in Florida, underlie the post-rift unconformity and represent part of a disjunct fragment of Gondwana that was sutured to the North American craton during the late Palaeozoic Alleghanian orogeny. The Palaeozoic strata are unconformably overlain by interbedded non-marine Jurassic (Bajocian and younger) sandstones and shales and marginal marine Lower Cretaceous sandstones, calcareous shales and carbonates, which contain scattered beds of coal and evaporite. Together, these rocks are stratigraphically equivalent to the onshore Fort Pierce and Cotton Valley(?) Formations and rocks of the Lower Cretaceous Comanchean Provincial Series. The abundance of carbonates and evaporites in this interval, which reflects marine influences within the embayment, increases upwards, eastwards and southwards. The Upper Cretaceous part of the section is composed mainly of neritic calcareous shales and shaley limestones stratigraphically equivalent to the primarily marginal marine facies of the onshore Atkinson, Cape Fear and Middendorf Formations and Black Creek Group, and to limestones and shales of the Lawson Limestone and Peedee Formations. Cenozoic strata are primarily semiconsolidated marine carbonates. Palaeocene to middle Eocene strata are commonly cherty; middle Miocene to Pliocene strata are massive and locally phosphatic and glauconitic; Quaternary sediments are dominated by unconsolidated carbonate sands. The effects of eustatic changes and shifts in the palaeocirculation are recorded in the Upper Cretaceous and Tertiary strata.

Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi‐channel seismic data

We present results from a coincident wide‐angle and deep‐penetrating, multichannel reflection seismic experiment conducted on the continental shelf of the Southeast Georgia Embayment. Over 5000 air gun shots were recorded by a 6‐km‐long, towed streamer and six ocean bottom seismic instruments along a ∼250‐km, north‐south profile crossing the Brunswick magnetic anomaly (BMA). These data indicate a transition in seismic properties across the BMA, including higher seismic velocities south of the BMA, particularly in the upper crust (7–15 km depth), and a transition from reflective to transparent crust from north to south. We interpret this transition to indicate an increased mafic content in crust south of the BMA. Magnetic modeling based on our seismic results indicates that the BMA may be explained as an edge effect anomaly of the more mafic upper crust. We suggest that the increased mafic content toward the south is due to rift‐related mafic intrusion. An alternative interpretation is discussed in which the seismic transition across the BMA is related to an Alleghanian suture. Athough there is no direct indication in the data for the association of the BMA and an Alleghanian suture along our profile, such an association cannot be ruled out. The southern portion of the profile crosses the margin hinge zone, where we observe seaward dipping reflectors similar to those observed along the northern Blake Plateau Basin and Carolina Trough hinge zones, which have been interpreted as volcanic sequences. Our seismic data include no evidence for very high velocity (>7.0 km/s) mid‐crust to lower‐crust inboard of the hinge zone such as is observed in the Carolina Trough outboard of the hinge zone. This indicates that the volume of emplaced mafic material changes dramatically across the hinge zone and suggests that rift‐related magmatic processes along the margin were highly focused.

Crustal structure of the Southeast Georgia embayment-Carolina trough: Preliminary results of a composite seismic image of a continental suture(?) and a volcanic passive margin

New deep-penetration multichannel seismic reflection data, combined with refraction results and magnetics modeling, support a hypothesis that the Carolina trough is a Mesozoic volcanic passive margin exhibiting a seaward-dipping wedge and associated underplating. The structure of Carolina platform continental crust is consistent with the late Paleozoic continental collision that produced the Appalachians, but imbrication has had no obvious effect on shallower structures produced by Mesozoic extension and volcanism. The origin of prominent magnetic anomalies crossing the Southeast Georgia embayment can be explained by processes attending Mesozoic separation of Africa and North America, and is not related to a Paleozoic continental suture, as previously postulated.

Oil and Gas Developments in Atlantic Coastal Plain and Outer Continental Shelf in 1985 and 1986

Exploratory drilling in the Atlantic coastal plain region increased in 1981. Eight wells were drilled, 5 of which were completed for a total footage of 71,439 ft (21,780 m). Four of the wells were located in the Baltimore Canyon Trough area and 4 were located in the Georges Bank basin. No exploratory wells were drilled in the Southeast Georgia Embayment or in the onshore portion of this region in 1981. The 5 completed wells were reported as dry holes. Two lease sales were held in 1981: OCS Lease Sale 56 drew bids on 47 tracts for a total of $342,766,174 in the South Atlantic and OCS Lease Sale 59 drew bids on 50 tracts for a total of $321,981,000 in the Mid-Atlantic. Geophysical activity provided a total of 24,470 line-mi (39,380 line-km) of seismic data.

Geologic Evaluation of Leasing on Atlantic Outer Continental Shelf: ABSTRACT

To date, 9,160 tracts, totaling 51.7 million ac, have been offered for lease in the Atlantic. Of the 506 tracts receiving bids, 410--totaling 2.3 million ac--were leased for a total bonus of $2.8 billion. There have been four Mid-Atlantic sales, three South Atlantic sales, and one North Atlantic sale, with one reoffering sale in the Mid-and South Atlantic. Resource potential for proposed North Atlantic sales centers around the Georges Bank basin and the Upper Jurassic shelf edge (reef trend). Associated with the reef trend are a series of back-reef anticlines, faults, and pinch-outs. Cross sections indicate post-rift depocenters affected by block faulting and salt movement. Eight exploratory wells, all dry, and two continental offshore stratigraphic test (COST) wells have been drilled in the area. Thirty-two exploratory wells have been drilled in the Mid-Atlantic in the Baltimore Canyon Trough. Targets have included an intrusive dome, fault blocks, deep-seated diapirs, and the Jurassic shelf-edge reef trend. Two COST wells were drilled, one encountering a show of gas. Five of the exploratory wells tested hydrocarbons, the others were dry. The Carolina Trough appears to offer the best resource potential in the South Atlantic even though it has yet to be drilled. It has sufficient sediment thickness, a regional salt bed producing a number of diapirs on the seaward edge of the basin, and growth faults associated with the salt flow that may provide other traps. The Blake Plateau offers some stratigraphic trap possibilities and may contain thermally mature sediments. However, no wells have been drilled in the basin. The Southeast Georgia embayment consists of a thin sedimentary section of mainly Cretaceous continental clastics and Paleozoic metasedimentary basement rocks. Six exploratory wells, all dry, and one COST well have been drilled in this basin. End_of_Article - Last_Page 1435------------

Exploration History and Future Prospects of United States Atlantic Margin: ABSTRACT

The Atlantic Margin of the United States comprises four large basins that are, from north to south, Georges Bank basin, Baltimore Canyon Trough, Carolina Trough, and Blake Plateau basin (which includes the Georgia Embayment and Bahama Platform). Most exploratory drilling has focused on structures in the postrift basin depocenters, with eight Georges Bank wildcats having been drilled into structures formed by block faulting and salt movement. Target zones were Upper and Middle Jurassic sandstones and carbonates. All were dry holes with some minor gas shows. Twenty-nine exploratory wells have been drilled into four types of structures in Baltimore Canyon Trough: an intrusive dome, deep-seated diapirs, fault blocks, and most recently a Lower Cretaceous-Upper Jurassic shelf-e ge reef. Some hydrocarbons were associated with a deep-seated diapir structure, but the other wells were dry. Wells in the Southeast Georgia Embayment penetrated Lower Cretaceous-Upper Jurassic continental clastics and shallow Paleozoic basement rocks. All wells were dry. No exploratory wells have been drilled in the Carolina Trough or Blake Plateau. Recent leasing in Georges Bank has been delayed because of litigation. In the Baltimore Canyon Trough, most recent leasing appears targeted at a prominent Lower Cretaceous-Upper Jurassic paleo-shelf edge, where it is hoped that synrift deposits rich in organic matter source porous shelf-edge carbonates and overlying clastics. Shell Oil, the largest leaseholder, is drilling a series of wells to test this structure. Between the Baltimore Canyon and Carolina Troughs, several leases have been taken over a large anticline possibly cored by salt. Another block of leases has been taken in the Carolina Trough immediately south of Cape Fear over a large grabenlike structure. Other, smaller groups of blocks appear to have lesser structures as targets. The Blake Plateau as yet has no active leas s. End_of_Article - Last_Page 1207------------

Petroleum Potential of Continental Margin off Southeastern United States: ABSTRACT

The continental margin off the southeastern United States is underlain by two major basins, the Carolina trough off North Carolina and South Carolina and the Blake Plateau Basin off Florida and Georgia, with the latter basin's landward extension, the Southeast Georgia embayment. The embayment, beneath the continental shelf is the only area in which drilling has taken place. Strata of the landward part of the Blake Plateau Basin including the embayment form a wedge of onlapping marine End_Page 563------------------------------ deposits that might provide stratigraphic traps, such as pinch-outs, barrier islands, and channels. Drapes over basement highs might trap petroleum. The seaward part of the Blake Plateau Basin contains a thick (14 km), landward-dipping section, probably composed mainly of carbonate platform deposits. Carbonate banks and an Albian-Aptian rudist reef might provide traps, although the seaward part of the platform has been breached by erosion. In the Carolina trough, flow of Jurassic(?) salt has formed diapirs, and withdrawal of salt has caused a large growth fault complex to form along the landward side of the trough. Because the block of sedimentary rock (12 km thick) above the salt is subsiding almost vertically, structures at the fault may include compressional features. The diapirs and faults may provide traps. A large shelf-edge anticline exists more than 150 km long and with a closure of as much as 500 m. Other possible traps might result from stratigraphic features of the onlapping sedimentary wedge landward of the Carolina trough and the eroded and buried paleoslope on the seaward side of the trough. End_of_Article - Last_Page 564------------

Oil and Gas Developments in Atlantic Coastal Plain and Outer Continental Shelf in 1981

Exploratory drilling in the Atlantic coastal plain region increased in 1981. Eight wells were drilled, 5 of which were completed for a total footage of 71,439 ft (21,780 m). Four of the wells were located in the Baltimore Canyon Trough area and 4 were located in the Georges Bank basin. No exploratory wells were drilled in the Southeast Georgia Embayment or in the onshore portion of this region in 1981. The 5 completed wells were reported as dry holes. Two lease sales were held in 1981: OCS Lease Sale 56 drew bids on 47 tracts for a total of $342,766,174 in the South Atlantic and OCS Lease Sale 59 drew bids on 50 tracts for a total of $321,981,000 in the Mid-Atlantic. Geophysical activity provided a total of 24,470 line-mi (39,380 line-km) of seismic data.

Seismic reflection data available

High‐resolution seismic reflection data are now available for the area offshore the southeast Georgia embayment associated with Outer Continental Shelf (OCS) lease sale 56.Approximately 6400 km of high‐resolution data were gathered from 286 tracts that covered 1,625,251 million acres in water depths from 14 m to 2025 m. These data were gathered to help evaluate the geological hazards related to oil and gas development in the area.

Atlantic Coastal Plain

Exploratory drilling in the Atlantic coastal plain region decreased in 1980. Seven wells were drilled, five of which were completed, for a total footage of 80,968 ft (24,679 m). Six of the wells were located in the Baltimore Canyon Trough, and one was located in the Southeast Georgia Embayment. No exploratory wells were drilled in the Georges Bank Basin or in the onshore portion of this region in 1980. Tenneco and Exxon reported gas shows in two wells in the Baltimore Canyon Trough; the remaining completed wells were reported as dry holes. No lease sales were held in 1980, but two sales are scheduled for 1981 in the Middle and South Atlantic.

Frontier Exploration--Southeast Georgia Embayment: ABSTRACT

During 1978 Transco Exploration Co. and its partners successfully bid on five Sale 43 tracts in the Southeast Georgia Embayment. These leases were acquired on the basis of a subunconformity play different from other prospects in the sale area. During late 1979 Transco, as operator, drilled an exploratory well which will influence future exploration of the prospect. End_of_Article - Last_Page 1659------------

The Georgia Embayment continental shelf: Stratigraphy of a submergence

Forty vibracores taken across the continental shelf and in proposed drilling lease areas of the southeast Georgia Embayment are used to document the unconsolidated shelf-sediment cover. The Holocene-Pleistocene sediment veneer is thin, generally less than 4 m thick. Lagoon sediments deposited during the last regression (shelf emergence) or the Holocene transgression (shelf submergence) occur in patches on the inner and central shelf. Because essentially only late Pleistocene and Holocene mollusk shells are present in the shelf-sediment cover, it is believed that most of the carbonate fraction was removed by subaerial leaching during low sea-level stands aided by mechanical abrasion and biological degradation during the regressive-transgressive cycle. During each transgression or submergence, the surficial sand sheet is recharged with a new biogenic carbonate fraction along with the addition of small amounts of clastic sediments derived from “overrun” estuaries and erosion of underlying Tertiary sediments. The stratigraphy based on the vibracores supports the concept of cross-shelf migration of the shore face—barrier island systems in response to rising sea level. Sedimentologic and paleontologic analyses also indicate that extensive in-place mixing of shelf sediments may have occurred, an important factor to consider in evaluation of the fate of particulate pollutants. The establishment of the time frame of such mixing should be given high priority in future studies.

Developments in Atlantic Coastal Plain in 1979

The year 1979 was the second for exploratory drilling on the U.S. Atlantic Outer Continental Shelf (OCS). Eighteen exploratory wells and the COST B-3 well were completed for a total of 250,038 ft (76,212 m) of drilling; 14 of these were located offshore New Jersey in the Baltimore Canyon Trough; the remaining 5 were drilled offshore Georgia in the Southeast Georgia Embayment. No exploratory wells for oil and gas were drilled onshore in 1979. Operators of 3 wells reported significant shows in the Baltimore Canyon; the remaining wells were reported as dry holes. OCS Lease Sale 42 drew bids on 73 tracts for a total of $827,632,188 in the Georges Bank basin. Geophysical activity totaled 3,246 line-mi (5,223 km) in 19.3 crew-weeks.

Developments in Atlantic OCS in 1978: ADDENDUM

The year 1978 marked the first year of exploratory drilling on the U.S. Atlantic OCS. Seven exploratory wells were completed in the Baltimore Canyon Trough (offshore New Jersey) for a total of 106,094 ft (32,337 m) of drilling. Of these wells, 1 tested gas, another reported minor gas shows, and the remaining 5 were plugged, having no reported shows. Six wells were being drilled or tested at year end, including the COST B-3 well. OCS Lease Sale 43, in the Southeast Georgia Embayment, resulted in an award of 43 tracts for a total of $101,743,443 in bids. Geophysical activity totaled 13,331 line-mi (21,450 km) in 48.86 crew-weeks.

Petroleum Geochemistry and Geology of Southeast Georgia Embayment and Florida-Hatteras Slope: ABSTRACT

End_Page 1583------------------------------Petroleum geochemical and geologic studies were carried out on the COST GE-1 well (Southeast Georgia Embayment), and on the Atlantic Margin Coring Project (AMCOR) core 6004 on the Florida-Hatteras slope. Mud additives contaminated some of the COST GE-1 samples, but by analyzing several duplicate handpicked sample suites the effect, although not totally removed, was minimized. In the COST well, the Tertiary shale-chalk-limestone section to a depth of approximately 1,088 m contains very small quantities of indigenous, biogenic hydrocarbons that are not believed to have had a thermal-chemical history. Upper Cretaceous rocks (Maestrichtian, Campanian, Santonian, Coniacian, and Turonian) from 1,088 to 1,814 m consist of gray, calcareous deep-water shales that contain the most organic-rich intervals in the well which are composed of thermally immature, amorphous, hydrogen-rich algal marine kerogens. If these Upper Cretaceous rocks were buried more deeply or found in a region of higher thermal gradient, they could be significant potential oil and gas source rocks. The Lower Cretaceous sedimentary rocks from 1,814 to 2,700 m are dominantly of continental origin wi h intercalated marine carbonate and sand units that contain very small amounts of terrestrial organic matter (less than 0.1% organic carbon). Although the kerogen in these rocks is of marginal thermal maturity, it promises little as a potential petroleum or natural-gas source. Sediments in the AMCOR hole 6004 range from Holocene to Upper Cretaceous and are of a predominantly outer shelf-upper slope depositional character. The hydrocarbon and fatty-acid distributions and molecular compositions are typical of marine biogenic sources that are thermally immature with regard to petroleum generation. The organic geochemistry of Paleocene sediments taken from the AMCOR core 6004 may reflect the influence of erosion by the ancestral Gulf Stream. End_of_Article - Last_Page 1584------------

Important Stratigraphic Breaks in COST GE-1 Well, Southeast Georgia Embayment: ABSTRACT

A foraminiferal analysis of the recently completed Continental Offshore Stratigraphic Test (COST) GE-1 well reveals that ~1,000 m of Cenozoic, ~700 m of Upper Cretaceous, and ~1,600 m of Lower Cretaceous sedimentary rocks lie above Devonian metamorphic basement in this part of the Southeast Georgia embayment. Seven regional hiatuses interrupt the depositional record and correspond to times of low global sea level. The hiatuses are between Albian and Turonian rocks; upper Maestrichtian and upper Paleocene; upper Paleocene and lower Eocene; upper Eocene and lower Oligocene; middle Oligocene and middle Miocene; middle Miocene and upper Pliocene; and upper Pliocene and lower Pleistocene. The depositional environments represented in the GE-1 well range from terrestrial nonfoss liferous biotopes to ocean depths equivalent to those of a modern continental slope. Most of the Cenozoic and Upper Cretaceous rocks accumulated in continental-shelf biotopes, but the Lower Cretaceous rocks are largely nonmarine and marginal-marine deposits. The sequence of paleo-environments can be correlated with the supercycles of global sea-level change outlined by P. Vail et al. Sediment-accumulation rates were highest (5.0 to 6.4 cm/1,000 years) during the Albian through Santonian interval, the middle and late Eocene, and the middle Miocene. Lowest rates (1.3 to 2.5 cm/1,000 years) prevailed during the Campanian and Maestrichtian, the early and middle Oligocene, and the Pleistocene. Subsidence calculations reveal that Cretaceous subsidence was more rapid than that of the Cenozoic, hat most of the major paleobathymetric changes were caused by eustatic sea-level fluctuations, and that subsidence rate of the embayment was sensitive to sediment loading and unloading. End_of_Article - Last_Page 510------------