Ruhlin, D. E., and Owen, R. M., 1986. The rare earth geochemistry
of hydrothermal sediments from the East Pacific Rise: examination of a seawater scavenging mechanism. Geochimica et
Cosmochimica Acta, 50, 393–400.
Sacchetti, F., Benetti, S., Quinn, R., and Cofaigh, C. O., 2013. Glacial and post-glacial sedimentary processes in the Irish Rockall
Trough from an integrated acoustic analysis of near-seabed sediments. Geo-Marine Letters, 33, 49–66.
Scheidegger, K. F., Corliss, J. B., Jezek, P. A., and Ninkovich, D.,
1980. Compositions of deep-sea ash layers derived from North
Pacific volcanic arcs: variations in time and space. Journal of
Volcanology and Geothermal Research, 7, 107–137.
Stonecipher, S. A., 1976. Origin, distribution, and diagenesis of
phillipsite and clinoptilolite in deep-sea sediments. Chemical
Geology, 17, 307–318.
Tominaga, M., Lyle, M., and Mitchell, N. C., 2011. Seismic interpretation of pelagic sedimentation regimes in the 18-53 Ma eastern equatorial Pacific: basin-scale sedimentation and infilling of
abyssal valleys. Geochemistry, Geophysics, Geosystems, 12,
Q03004, p. 22.
Torres, M. E., McManus, J., and Huh, C.-A., 2002. Fluid seepage
along the San Clemente Fault scarp: basin-wide impact on barium cycling. Earth and Planetary Science Letters, 203,
181–194.
van Andel, T. H., and Moore, T. C., Jr., 1974. Cenozoic calcium carbonate distribution and calcite compensation depth in the central
equatorial Pacific Ocean. Geology, 2, 87–92.
Walsh, I., Fischer, K., Murray, D., and Dymond, J., 1988. Evidence
for resuspension of rebound particles from near-bottom sediment
traps. Deep Sea Research, 35, 59–70.
Wheat, C. G., Feeley, R. A., and Mottl, M. J., 1996. Phosphate
removal by oceanic hydrothermal processes: an update of the
phosphorus budget of the oceans. Geochimica et Cosmochimica
Acta, 60, 3593–3608.
Whittaker, J., Goncharov, A., Williams, S., Müller, R. D., and
Leitchenkov, G., 2013. Global sediment thickness dataset
updated for the Australian-Antarctic Southern Ocean, Geochemistry, Geophysics. Geosystems, 14, 3297–3305, doi:10.1002/
ggge.20181.
Williams, D. L., and Von Herzen, R. P., 1974. Heat loss from the
earth: new estimate. Geology, 2, 327–328.
Zaric, S., Donner, B., Fischer, G., Mulitza, S., and Wefer, G., 2005.
Sensitivity of planktonic foraminifer to sea surface temperature
and export production as derived from sediment trap data.
Marine Micropaleontology, 55, 75–105.
Cross-references
Bouma Sequence
Continental Rise
Continental Slope
Deep-sea Sediments
Submarine Canyons
Turbidites
DELTAS
Duncan FitzGerald
1
, Ioannis Georgiou
2 and Mark Kulp
2
1
Department of Earth and Environment, Boston
University, Boston, MA, USA
2
Department of Earth and Environmental Sciences,
University of New Orleans, New Orleans, LA, USA
Synonyms
River-mouth deposits
Definition
As defined by Moore and Asquith (1971), a delta is the
subaerial and submerged contiguous sediment mass
deposited in a body of water (ocean or lake) primarily by
the action of a river. Wright (1985) added that deltas
included secondary riverine-derived deposits that had
been reworked and molded by waves, currents, or tides.
The term delta, for the sedimentary accumulation at a
river mouth, was coined by the Greek historian Herodotus
who in the fifth century recognized a similarity in shape of
the Greek letter D to the tract of land at the mouth of the
Nile River (The Histories, 450–420 AD). Although the
distinctive morphology is lacking in many river-mouth
land tracts, the term has become accepted to describe both
the geographical region near a river mouth and the sedimentary package deposited by fluvial processes into a
depositional basin. Although sediment delivery to a delta
is by a fluvial system, the dynamic interaction of riverine
and ocean processes controls morphologic, stratigraphic,
and sedimentologic variability of deltaic environments.
Deltaic environments exist throughout the world and have
been widely recognized in the sedimentary rock record.
Buried deltaic sandstones are associated with reservoir
rocks containing many of the world’s major natural gas
and oil resources (Morse, 1994). Modern deltas have
abundant food sources derived from diverse flora and
fauna, extensive cultivable land, and navigable waterways
reaching from the coast to interiors of continents. Thus,
these settings became the centers of numerous formative
cultures and today are the home to some of the densest
populations in the world. It is estimated that approximately 61 % of the world’s population live on deltas and
that percentage continues to grow (Bianchi and Allison,
2009). Deltaic systems are also recognized as important
carbon sinks due to burial of vegetative detritus coming
down rivers as well as phytoplankton blooms spawned
by nutrient-rich waters. Thus, the progradation or erosional reworking and retreat of deltas affects the carbon
budget and climate change.
Globally, deltas are found on all continents and in all
climates (Figure 1). In a general sense, the locations of
deltas are similar, at the terminus of a catchment basin that
provides sediment load into an ocean, gulf, lagoon, estuary, or lake. Although a delta may form regardless of the
size of the fluvial system or receiving basin, some tectonic
settings are more conducive than others to the development of major deltaic landscapes. Using the Inman and
Nordstrom (1971) tectonic classification of coasts,
trailing-edge coasts typically have the largest drainage
basins followed by marginal-sea coasts, and the smallest
are common to leading-edge coasts. Of the 58 major river
systems in the world with drainage areas greater than
10
5 km
2
, 56.9 % occur on trailing-edge coasts, 34.5 %
DELTAS
171
of hydrothermal sediments from the East Pacific Rise: examination of a seawater scavenging mechanism. Geochimica et
Cosmochimica Acta, 50, 393–400.
Sacchetti, F., Benetti, S., Quinn, R., and Cofaigh, C. O., 2013. Glacial and post-glacial sedimentary processes in the Irish Rockall
Trough from an integrated acoustic analysis of near-seabed sediments. Geo-Marine Letters, 33, 49–66.
Scheidegger, K. F., Corliss, J. B., Jezek, P. A., and Ninkovich, D.,
1980. Compositions of deep-sea ash layers derived from North
Pacific volcanic arcs: variations in time and space. Journal of
Volcanology and Geothermal Research, 7, 107–137.
Stonecipher, S. A., 1976. Origin, distribution, and diagenesis of
phillipsite and clinoptilolite in deep-sea sediments. Chemical
Geology, 17, 307–318.
Tominaga, M., Lyle, M., and Mitchell, N. C., 2011. Seismic interpretation of pelagic sedimentation regimes in the 18-53 Ma eastern equatorial Pacific: basin-scale sedimentation and infilling of
abyssal valleys. Geochemistry, Geophysics, Geosystems, 12,
Q03004, p. 22.
Torres, M. E., McManus, J., and Huh, C.-A., 2002. Fluid seepage
along the San Clemente Fault scarp: basin-wide impact on barium cycling. Earth and Planetary Science Letters, 203,
181–194.
van Andel, T. H., and Moore, T. C., Jr., 1974. Cenozoic calcium carbonate distribution and calcite compensation depth in the central
equatorial Pacific Ocean. Geology, 2, 87–92.
Walsh, I., Fischer, K., Murray, D., and Dymond, J., 1988. Evidence
for resuspension of rebound particles from near-bottom sediment
traps. Deep Sea Research, 35, 59–70.
Wheat, C. G., Feeley, R. A., and Mottl, M. J., 1996. Phosphate
removal by oceanic hydrothermal processes: an update of the
phosphorus budget of the oceans. Geochimica et Cosmochimica
Acta, 60, 3593–3608.
Whittaker, J., Goncharov, A., Williams, S., Müller, R. D., and
Leitchenkov, G., 2013. Global sediment thickness dataset
updated for the Australian-Antarctic Southern Ocean, Geochemistry, Geophysics. Geosystems, 14, 3297–3305, doi:10.1002/
ggge.20181.
Williams, D. L., and Von Herzen, R. P., 1974. Heat loss from the
earth: new estimate. Geology, 2, 327–328.
Zaric, S., Donner, B., Fischer, G., Mulitza, S., and Wefer, G., 2005.
Sensitivity of planktonic foraminifer to sea surface temperature
and export production as derived from sediment trap data.
Marine Micropaleontology, 55, 75–105.
Cross-references
Bouma Sequence
Continental Rise
Continental Slope
Deep-sea Sediments
Submarine Canyons
Turbidites
DELTAS
Duncan FitzGerald
1
, Ioannis Georgiou
2 and Mark Kulp
2
1
Department of Earth and Environment, Boston
University, Boston, MA, USA
2
Department of Earth and Environmental Sciences,
University of New Orleans, New Orleans, LA, USA
Synonyms
River-mouth deposits
Definition
As defined by Moore and Asquith (1971), a delta is the
subaerial and submerged contiguous sediment mass
deposited in a body of water (ocean or lake) primarily by
the action of a river. Wright (1985) added that deltas
included secondary riverine-derived deposits that had
been reworked and molded by waves, currents, or tides.
The term delta, for the sedimentary accumulation at a
river mouth, was coined by the Greek historian Herodotus
who in the fifth century recognized a similarity in shape of
the Greek letter D to the tract of land at the mouth of the
Nile River (The Histories, 450–420 AD). Although the
distinctive morphology is lacking in many river-mouth
land tracts, the term has become accepted to describe both
the geographical region near a river mouth and the sedimentary package deposited by fluvial processes into a
depositional basin. Although sediment delivery to a delta
is by a fluvial system, the dynamic interaction of riverine
and ocean processes controls morphologic, stratigraphic,
and sedimentologic variability of deltaic environments.
Deltaic environments exist throughout the world and have
been widely recognized in the sedimentary rock record.
Buried deltaic sandstones are associated with reservoir
rocks containing many of the world’s major natural gas
and oil resources (Morse, 1994). Modern deltas have
abundant food sources derived from diverse flora and
fauna, extensive cultivable land, and navigable waterways
reaching from the coast to interiors of continents. Thus,
these settings became the centers of numerous formative
cultures and today are the home to some of the densest
populations in the world. It is estimated that approximately 61 % of the world’s population live on deltas and
that percentage continues to grow (Bianchi and Allison,
2009). Deltaic systems are also recognized as important
carbon sinks due to burial of vegetative detritus coming
down rivers as well as phytoplankton blooms spawned
by nutrient-rich waters. Thus, the progradation or erosional reworking and retreat of deltas affects the carbon
budget and climate change.
Globally, deltas are found on all continents and in all
climates (Figure 1). In a general sense, the locations of
deltas are similar, at the terminus of a catchment basin that
provides sediment load into an ocean, gulf, lagoon, estuary, or lake. Although a delta may form regardless of the
size of the fluvial system or receiving basin, some tectonic
settings are more conducive than others to the development of major deltaic landscapes. Using the Inman and
Nordstrom (1971) tectonic classification of coasts,
trailing-edge coasts typically have the largest drainage
basins followed by marginal-sea coasts, and the smallest
are common to leading-edge coasts. Of the 58 major river
systems in the world with drainage areas greater than
10
5 km
2
, 56.9 % occur on trailing-edge coasts, 34.5 %
DELTAS
171