Sequence Stratigraphy

Sequence stratigraphy is the study of sediments and sedimentary rocks in terms of repetitively arranged facies and associated stratal geometry (Vail 1987; Van Wagoner et al 1988, 1990; Christie-Blick 1991). It is a technique that can be traced back to the work of Sloss et al ( 1949), Sloss ( 1950, 1963), and Wheeler ( 1958) on interregional unconformities of the North American craton, but it became systematized only after the advent of seismic stratigraphy, the stratigraphic interpretation of seismic reflection profiles (Vail et al 1977, 1984, 1991; Berg and Woolverton 1985; Cross and Lessenger 1988; Sloss 1988; Christie-Blick et al 1990; Van Wagoner et a11990; Vail 1992). Sequence stratigraphy makes use of the fact that sedimentary successions are pervaded by physical discontinuities. These are present at a great range of scales and they arise in a number of quite different ways: for example, by fluvial incision and subaerial erosion (above sea level); submergence of nonmarine or shallow-marine sediments during transgression (flooding surfaces and drowning unconformities), in some cases with shoreface erosion (ravinement); shoreface erosion during regression; erosion in the marine environment as a result of storms, currents, or mass-wasting; and through condensation under conditions of diminished sediment supply (intervals of sediment starvation), The main attribute shared by virtually all of these discontinuities, independent of origin and scale, is that to a first approximation they separate older deposits from younger ones. The recognition of discontinuities is therefore useful because they allow sedimentary successions to be divided into geometrical units that have time-stratigraphic and hence genetic significance

Extensional Tectonics in the Jeanne d'Arc Basin, Offshore Newfoundland: Implications for the Timing of Break-Up between Grand Banks and Iberia

Using seismic reflection and exploratory well data from the Jeanne d’Arc basin, offshore Newfoundland, we examined the link between unconformity generation and the onset of seafloor spreading between the central Grand Banks and Iberia. A prominent unconformity developed across the entire basin, previously interpreted as a ‘break-up’ unconformity, is reinterpreted as a late Barremian/early Aptian rift-onset unconformity on the basis of the stratal geometry and lithofacies. The rotation and divergence of seismic reflectors above this unconformity attest to differential subsidence documenting an episode of extension and block rotation within the basin at this time. Our seismic sequence analysis suggests that rifting and block rotation continued in the Jeanne d’Arc basin until at least late Aptian/early Albian time. The onset of seafloor spreading between the central Grand Banks and Iberia is uncertain because of limited marine magnetic and drilling data (ODP and DSDP), and the existence of the Cretaceous magnetic quiet zone along the margin. However, recent studies indicate that magnetic anomaly M0 (118 Ma) is not well resolved north of the Newfoundland Seamounts within the Newfoundland basin and is not present north of the Figueiro fracture zone along the conjugate Iberian margin. This suggests that seafloor spreading between the northern portion of the Newfoundland basin and the northern Iberian margin began after the early Aptian. Given that the cessation of rifting marks the onset of seafloor spreading our seismic sequence analysis indicates that the onset of seafloor spreading in the northern Newfoundland basin, north of the Newfoundland Seamounts, began after late Aptian time

Deglacial floods in the Beaufort Sea preceded Younger Dryas cooling

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Nature Geosciencevolume 11 (2018): 599-604, doi:10.1038/s41561-018-0169-6.The Younger Dryas cooling at ~13 ka, after 2 kyr of postglacial warming, is a century-old climate problem. The Younger Dryas is thought to have resulted from a slow-down of the Atlantic meridional overturning circulation in response to a sudden flood of Laurentide Ice Sheet meltwater that reached the Nordic Seas. Although there is no oxygen isotope evidence in planktonic foraminifera from the open western North Atlantic for a local source of meltwater from the Gulf of St. Lawrence where it was predicted, we report here that the eastern Beaufort Sea contains the long-sought signal of 18O-depleted water. Beginning at ~12.94 ± 0.15 ka, oxygen isotopes in planktonic foraminifera from two sediment cores as well as sediment and seismic data indicate a flood of melt water, ice and sediment to the Arctic via Mackenzie River that lasted about 700 years. The minimum in oxygen isotope ratios lasted ~130 years. The floodwater would have travelled north along the Canadian Archipelago, and through Fram Strait to the Nordic Seas where freshening and freezing near sites of deepwater formation would have suppressed convection, and caused the Younger Dryas cooling by reducing the meridional overturningThis research was funded by NSF grants ARC 1204045 to L.D.K., and ARC 1203944 to N.W.D

Anatomy and growth of a Holocene clinothem in the Gulf of Papua

High-resolution seismic profiles and sedimentological data from grab samples and long cores provide an unprecedented picture of the structure, sedimentology, and late Quaternary development of two Gulf of Papua ( GoP) clinothems, one probably Stage 3 and 4 in age and one Holocene in age. The older was partially eroded during Stage 2 and partially covered by the younger clinothem during Stage 1. The younger clinothem consists of three stratigraphic units separated by two surfaces of erosion, bypass, or correlative surfaces of lap. The surfaces were formed by changes in accommodation and sediment supply. The underlying physiography of the older clinothem also appears to play an important role in governing the shape of the younger clinothem. In the northern gulf, oblique clinoforms of the younger clinothem suggest that the rate of sediment supply from the northern rivers outstripped the formation of new accommodation, whereas in the south, sigmoidal clinoforms indicate that accommodation increased faster than sediment supply. The origin of the new accommodation remains uncertain because of limited age constraints. On the basis of sediment thickness, stratal geometry, and acoustic character, off-shelf transport appears to be the dominant sediment transport direction, with preferential accumulation on the promontories and bypass in the valleys. Presently, observed and computed modern flows and complex gyres in shallow water coupled with wave- and current-supported gravity flows or river floods can explain the form, internal clinoform shapes, and mineralogy of the younger Gulf of Papua clinothem

Building the Holocene clinothem in the Gulf of Papua: An ocean circulation study

This paper investigates the role that tidal and wind-driven flows and buoyant river plumes play in the development of the Holocene clinothem in the Gulf of Papua. Time series data from bottom tripods and a mooring were obtained at four locations near the mouth of the Fly River during portions of 2003 and 2004. Flows in the Gulf of Papua during calendar year 2003 were hindcast every 3 h using the Navy Coastal Ocean Model (NCOM) with boundary conditions from the Navy Atmospheric Prediction System, the east Asian seas implementation of NCOM, and the OTIS Tidal Inversion System. Results show that tidal flows on the modern clinoform are strong and are landward and seaward directed. Peak spring tidal velocities can provide the shear stresses necessary to keep sediment up to sand size in motion as the wind-driven and baroclinic currents distribute it from the river mouths across and along the shelf in two circulation states. During the monsoon season, the clinoform topset is swept by a seaward surface flow and landward bottom flow, reflecting river plumes and coastal upwelling. Seaward, this structure evolves into a SW directed surface current over the clinothem foreset with accompanying landward directed near-bed currents that trend obliquely up the foreset to the WSW over much of the clinothem. During the trade wind season, the inner and outer topset are swept by NE directed, contour-parallel surface currents, underneath which lie obliquely landward near-bed currents. These modeled flows and complex gyres in shallow water coupled with wave- and current-supported gravity flows or river floods can explain the form, internal clinoform shapes, and mineralogy of the modern Gulf of Papua clinothem

Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California

Subduction of the Farallon plate beneath northwestern Mexico stalled by ~12 Ma when the Pacific-Farallon spreading-ridge approached the subduction zone. Coupling between remnant slab and the overriding North American plate played an important role in the capture of the Baja California (BC) microplate by the Pacific Plate. Active-source seismic reflection and wide-angle seismic refraction profiles across southwestern BC (~24.5 degrees N) are used to image the extent of remnant slab and study its impact on the overriding plate. We infer that the hot, buoyant slab detached ~40 km landward of the fossil trench. Isostatic rebound following slab detachment uplifted the margin and exposed the Magdalena Shelf to wave-base erosion. Subsequent cooling, subsidence and transtensional opening along the shelf (starting ~8 Ma) starved the fossil trench of terrigenous sediment input. Slab detachment and the resultant rebound of the margin provide a mechanism for rapid uplift and exhumation of forearc subduction complexes

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina : implications for the regional sediment budget and long-term shoreline response

This paper is not subject to U.S. copyright. The definitive version was published in Continental Shelf Research 56 (2013): 56-70, doi:10.1016/j.csr.2013.02.004.High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ∼67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system

Continental rupture and the creation of new crust in the Salton Trough rift, Southern California and northern Mexico: Results from the Salton Seismic Imaging Project

A refraction and wide-angle reflection seismic profile along the axis of the Salton Trough, California and Mexico, was analyzed to constrain crustal and upper mantle seismic velocity structure during active continental rifting. From the northern Salton Sea to the southern Imperial Valley, the crust is 17–18 km thick and approximately one-dimensional. The transition at depth from Colorado River sediment to underlying crystalline rock is gradual and is not a depositional surface. The crystalline rock from ~3 to ~8 km depth is interpreted as sediment metamorphosed by high heat flow. Deeper felsic crystalline rock could be stretched preexisting crust or higher-grade metamorphosed sediment. The lower crust below ~12 km depth is interpreted to be gabbro emplaced by rift-related magmatic intrusion by underplating. Low upper mantle velocity indicates high temperature and partial melting. Under the Coachella Valley, sediment thins to the north and the underlying crystalline rock is interpreted as granitic basement. Mafic rock does not exist at 12–18 km depth as it does to the south, and a weak reflection suggests Moho at ~28 km depth. Structure in adjacent Mexico has slower midcrustal velocity, and rocks with mantle velocity must be much deeper than in the Imperial Valley. Slower velocity and thicker crust in the Coachella and Mexicali valleys define the rift zone between them to be >100 km wide in the direction of plate motion. North American lithosphere in the central Salton Trough has been rifted apart and is being replaced by new crust created by magmatism, sedimentation, and metamorphism