HIGH-RESOLUTION SEISMIC EVIDENCE FOR CHANGING SEDIMENTARY CONDITIONS
IN THE HUDSON RIVER ESTUARY, PIERMONT, NY
Angela L. Slagle ([email protected]), S.M. Carbotte, W.B. Ryan, R.E. Bell, F.O. Nitsche
Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, USA
596000
H30-4
3.75 m
Sparkill Creek Delta Deposit
Channel reflectors
W a. Line p2e076a
E
-400
-450
-450
3240 ± 90
-500
-550
-550
-600
-600
susceptibility
velocity
density
LOI
2400
0
2
-650
4
6
LOI (% dry mass)
8
-400
-500
-500
-600
-600
-700
-700
-800
-800
susceptibility
velocity
b.
-900
-900
800
10
density
LOI
1200
1600
2000
p-wave vel (m/sec)
2400
8
10
-250
-250
-300
-350
-350
-400
-400
-450
-450
-500
-500
-550
-550
-650
596000
b.
800
susceptibility
velocity
2400
0
4
6
LOI (% dry mass)
8
H11-4
H11-4
-150
-150
H11-5
-200
a. Line b2w032b
H11-5
-200
H11-6
Channel reflectors
-250
-250
E
3370 ± 75
oyster shell & fragments
H11-7
H11-7
-300
-300
-350
-350
-400
-400
-450
-450
-500
-500
-550
-550
10
3. Evidence of other Events
* Glacio-lacustrine clays sitting below estuarine sediments record
differential flooding of the shoreline by marine waters
(see Fig. 8a-b).
* Relic oyster beds (exposed, buried and eroded) show changes in
morphology and sedimentary conditions in the river
(see Fig. 9).
-600
-600
-650
susceptibility
velocity
b.
800
density
LOI
1200
1600
2000
p-wave vel (m/sec)
2400
0
2
4
6
LOI (% dry mass)
-650
8
10
a. Line b2n020b, north of Piermont Pier
S
d15
a: North-south line b2n020b, located north of Piermont Pier; locations of
CD02-C10 and CD02-C11 are projected onto profile, illustrating their position
in delta stratigraphy.
Piermont Pier
d17
b: North-south line b2n022c, located south of Piermont Pier; prominent reflectors
are d14-d21; note inflection point of deltaic sequence.
d20
d17 d18
3.75 m
Sparkill Creek Delta Deposit
S
80
Core CD01-01
1.0
1.2
density (g/cc)
1.4
1.6
1.8
Age in cal yr B.P.
0
Core CD01-01
2.0
Seismic
0
reflectors
magnetic susceptibility (SI)
0
40
80
120
-40
H01-1
0
oyster shells
H01-1
H01-2
-50
two-way travel time (s)
-50
H10-5(d5)
organic layers
H02-1
H02-2
H02-2
2220 ±100
-100
-100
organic layers
2360 ±300*
-150
-150
3.75 m
W
a. Line b2w040c
channel reflectors
oyster pinnacles
-200
E
H02-1
-250
Fig. 7b - Summary diagram for CD01-02, including bulk
density, magnetic susceptibility and p-wave
velocity. LOI is in progress. Calendar ages are
shown in blue and prominent seismic reflectors
are indicated in red.
CD01-02
-400
-400
-450
-450
-500
H02-3
2540 ±165
-550
-550
-600
b.
susceptibility
velocity
-600
density
LOI
-650
-650
800
1200
1600
2000
p-wave vel (m/sec)
2400
0
2
4
6
LOI (% dry mass)
8
10
1.4
density (g/cc)
1.6
1.8
2.0
2.2
Age in cal yr B.P.
2.4
Seismic
0
reflectors
H01-1
1060 ± 90
-50
oyster remnants
glacial lake clay
-150
H01-2
0.02
-150
H01-2
3.75 m
a. Line b2w036b
E
Fig. 8a - East-west seismic profile b2w036b
showing location of core CD01-01.
Prominent reflectors are H01-1 and
H01-2.
Fig. 8b - Summary diagram for CD01-01,
including bulk density, magnetic
susceptibility, p-wave velocity and LOI.
Ages and seismics shown as above.
-200
-200
-250
-250
-300
-300
-350
-350
-400
-400
-450
-450
-500
-500
-550
-550
-600
-600
-650
b.
800
1200
density
LOI
susceptibility
velocity
1600
2000
2400
p-wave vel (m/sec)
-650
2800
0
2
4
6
LOI (% dry mass)
8
10
1
CD02-C11
Sparkill Creek
Hudson River
Benthic Mapping Project
New York State Department
of Environmental Conservation
CD02-C30
Piermont, NY
CD02 cores
CD01 cores
delta - mapped reflections
delta - inferred from stratigraphy
delta isopachs (in meters)
oysters - exposed
oysters - submerged
oysters - eroded pinnacles
UTM projection -zone 18N
NAD83
CD02-C12
1:50,000
41°0'0"N
0
ACKNOWLEDGEMENTS
Research for this project is supported by the New York Department of Environmental Conservation and the Estuarine Reserves Division, Office of
Ocean and Coastal Resource Management, National Ocean Service, National Oceanic and Atmospheric Administration.
2
3 4
Piermont Pier
-100
-100
W
-350
1.2
0.015
H02-1
-250
-350
-500
H02-3
0.01
0.025
H02-2
oyster shells
1.0
-50
-200
-300
-300
H02-2
Fig. 7a - East-west seismic profile b2w040c showing location
of core CDO01-02. Prominent reflectors are H02-1
through H02-3.
73°51'0"W
CD01-01
4545000
-20
596000
73°52'0"W
CD02-C10
Core CD01-02
Core CD01-02
595000
Tappan Zee Bridge
b. Line b2n022c, south of Piermont Pier N
magnetic susceptibility (SI)
0
20
40
60
594000
73°53'0"W
41°2'0"N
d16
d19
d21
d19
d18
593000
73°54'0"W
500
m
1,000
41°0'0"N
two-way travel time (s)
inflection point
d16
H11-7(d14)
N
592000
4548000
Fig. 6 - Seismic profiles describing the Sparkill Creek deltaic sequence.
Deltaic sequence is numbered from youngest to oldest reflection, d1-d21.
event horizon
591000
73°55'0"W
41°4'0"N
H10-4(d3) H10-3(d2)
590000
73°56'0"W
41°5'0"N
oyster bed
CD02-C11
ABSTRACT
4549000
CD02-C10
d7 d6 H10-5(d5)
H11-4(d11)
H11-7(d14)
H11-6(d13)
Sparkill Creek Delta Deposit
Additional evidence of major change has been preserved and identified
in other areas of the Hudson River Estuary. Examples of two such events
found in Piermont and other areas are the presence of relic oyster beds
that have changed in depth and morphology, and evidence of glaciolacustrine clay layers underlying estuarine sediments, indicating that parts
of the area were subaerially exposed while other had already been flooded.
Further investigation of these events will lead to better distinction between
local events that affect only part of the estuary, and regional or global
events that affect the entire estuarine system.
2
H11-3
589000
Fig. 1 - Basemap of Piermont, NY, showing 100 kHz sidescan sonar data, key
seismic lines and sediment core sites. Details of seismic lines and cores
shown in Fig. 2 - 8.
A detailed analysis of high-resolution seismic reflection data from the
Piermont area of the Hudson River Estuary indicates major changes in
sedimentation during the Holocene. The dominant depositional feature
is a delta deposit sourced from Sparkill Creek, which enters the river
from the west through the Piermont Marsh. Integration of seismic data
with sediment cores provides spatial and temporal boundaries for the
delta. Preliminary analysis of 14C data indicate that the most recent
period of deposition occurred between 3370 and 2520 cal yr B.P.
Truncated reflections at the exposed surface of the delta demonstrate
that the deposit is no longer actively accreting and that the interval of
delta deposition was followed by a period of erosion. However, the
reasons for the onset and termination of this deposit are not yet clear.
These dramatic changes in sedimentary environment may be related to
variations in sediment supply from the Sparkill Creek, modification of its
watershed, or changes in estuary morphology.
H11-3
-650
1200
1600
2000
p-wave vel (m/sec)
-100
-100
H10-5(d5)
Fig. 5b - Summary diagram for CD02-C11, including bulk density, magnetic susceptibility p-wave
velocity and LOI. Calendar ages are shown in blue and prominent seismic reflectors are
indicated in red.
density
LOI
2750 ± 65
organic layers
Fig. 5a - East-west seismic profile b2w032b showing location of core CDO2-C11. Prominent
reflectors in CD02-C11 are H11-1 through H11-7, all part of the Sparkill Creek deltaic
sequence.
-600
-600
-50
H11-2
H11-6
W
-300
H11-2-50
depth down hole (cm)
-200
two-way travel time (s)
-200
3.75 m
H11-1
d4
2.0
Seismic
0
reflectors
H11-1
41°5'0"N
595000
-150
1.8
Age in cal yr B.P.
4548000
594000
73°51'0"W
Fig. 4a - East-west seismic profile p2w060a
showing location of core CDO2-C12.
Prominent reflectors are H12-1 to
H12-4.
Fig. 4b - Summary diagram for CD02-C12,
including bulk density, magnetic
susceptibility and p-wave velocity.
Ages and seismics shown as above.
-150
density (g/cc)
1.4
1.6
1.2
4547000
593000
73°52'0"W
E
H12-4
0
1.0
41°4'0"N
73°53'0"W
3.75 m
-100
H11-1(d8)
H11-2(d9)
H11-3(d10)
d7 d6
H11-4(d11)
H11-5(d12)
H11-6(d13)
H11-7(d14)
Sparkill Creek Delta Deposit
80
4546000
73°54'0"W
730 ± 65
-100
oyster beds
magnetic susceptibility (SI)
0
20
40
60
-20
41°3'0"N
Lamont-Doherty Earth Observatory
of Columbia University
SUNY Stony Brook
H12-3
H12-4
Sparkill Creek Delta Deposit
Core CD02-C11
-50H12-2
H12-3
H12-3
acoustically transparent drape
4544000
p2w060a
592000
4
6
LOI (% dry mass)
41°2'0"N
41°0'0"N
1,000 m
591000
2
4543000
CD02-C12
Seismic
2.0
reflectors
0
H12-1
1.8
depth down hole (cm)
4540000
1:50,000
1.2
two-way travel time (s)
PIERMONT, NY
UTM projection -zone 18N
NAD83
1.0
depth down hole (cm)
Seismic tracks
80
H12-2
-50
depth down hole (cm)
two-way travel time (s)
4543000
4542000
41°1'0"N
b2n022c
CD01 cores
73°55'0"W
0
2. Sedimentary Environment
* During deltaic interval, Piermont area is actively depositional;
delta deposit is pushing channel eastward, and loading the flats
west of the channel.
* In modern environment, only localized regions of erosion and
deposition are found (associated with anthropogenic structures,
i.e. Piermont Pier, Tappan Zee Bridge).
4545000
1200
1600
2000
p-wave vel (m/sec)
-400
4544000
b.
-300
Lamont-Doherty Earth Observatory
of Columbia University
SUNY Stony Brook
73°56'0"W
589000
590000
4543000
-650
Fig. 3b - Summary diagram for CD02-C30, including
bulk density, magnetic susceptibility and
p-wave velocity. Prominent seismic reflectors
are indicated in red. Dating is in progress.
-300
4542000
oyster shells
-500
Fig. 3a - East-west seismic profile p2e076a showing
location of core CDO2-C30. Prominent
reflectors are H30-1 through H30-6.
H30-5
H30-6
4549000
-400
-200
H30-5
H30-6
H10-5
-350
H30-4
-200
Core CD02-C11
density (g/cc)
1.4
1.6
Age in cal yr B.P.
H12-1
H12-1
H12-2
H12-4
magnetic susceptibility (SI)
0
20
40
60
0
W a. Line p2w060a Channel reflectors
4541000
p2w076a
- Side-Scan Sonar -
41°1'0"N
Core CD02-C12
CD02-C30
Piermont, NY
41°0'0"N
H30-4
H30-5
H30-3
4541000
Fig. 2b - Summary diagram for CD02-C10, including bulk density, magnetic
susceptibility, p-wave velocity and LOI. Calendar ages are shown in blue
and prominent seismic reflectors are indicated in red.
H30-3
H30-6
-300
H10-5
-100
oyster shell
1. Sparkill Creek Delta Deposit
* Sedimentation rate of 3-4 mm/yr, compared to 1-2 mm/yr
average rate for the estuary.
* Youngest deltaic sediments deposited 2520 yr B.P.
* Oldest dated horizon (H11-14) deposited 3370 yr B.P.
* 41 x 106 m3 sediment deposited in ~850 yr; this would
require 1.5 m of erosion from entire watershed in that time.
* Preliminary data indicate higher organic carbon content in
deltaic sediments (see Fig. 2b, 4b, 8b).
4542000
4546000
Fig. 2a - East-west seismic profile b2w038c showing location of core CDO2-C10.
Prominent reflectors in CD02-C10 are H10-1 through H10-5, the youngest
reflectors in the Sparkill Creek deltaic sequence.
4545000
41°3'0"N
41°2'0"N
41°2'0"N
4543000
Hudson River
Benthic Mapping Project
New York State Department
of Environmental Conservation
4542000
E
H30-2
4540000
a. Line b2w038c
H10-4
2730 ± 50
oyster shells
-300
H30-2
41°1'0"N
W
Channel reflectors
H30-1
-100
-250
H10-3
H30-1
d15
H10-2
-250
2.0
Seismic
0
reflectors
4547000
H10-2
1.8
Age in cal yr B.P.
Core CD02-C12
CD02 cores
4541000
-200
-200
1.2
41°3'0"N
3.75 m
Sparkill Creek Delta Deposit
-150
organic layers
1.0
41°1'0"N
-150
80
density (g/cc)
1.4
1.6
4546000
possible event horizons
-20
4540000
-100
-100
Sparkill Creek
590000
-20
0
H30-1
H30-2
d16 d17
magnetic susceptibility (SI)
0
20
40
60
4544000
4544000
H10-1
H10-2(d1)
H10-3(d2)
H10-4(d3)
H10-5(d5)
H10-1
800
Piermont Pier
589000
Core CD02-C30
2.0
Seismic
0
reflectors
-50
H10-4
CD02-C11
73°56'0"W
1.8
H10-3
b2w032b
500
1.2
H30-3
CD02-C10
CD01-01
0
1.0
H10-1
4547000
41°4'0"N
b2w040c
b2w038c
41°3'0"N
4545000
Core CD02-C10
80
Age in cal yr B.P.
0
SUMMARY of KEY DATA
Core CD02-C30
density (g/cc)
1.4
1.6
-350
CD01-02
b2w036b
-20
magnetic susceptibility (SI)
0
20
40
60
-50
4548000
41°5'0"N
4546000
41°4'0"N
b2n020b
4547000
Tappan Zee Bridge
Core CD02-C10
4541000
73°51'0"W
41°5'0"N
73°52'0"W
4540000
595000
depth down hole (cm)
594000
73°53'0"W
two-way travel time (s)
593000
73°54'0"W
depth down hole (cm)
592000
two-way travel time (s)
591000
73°55'0"W
4549000
590000
73°56'0"W
4548000
4549000
589000
73°55'0"W
591000
73°54'0"W
592000
73°53'0"W
593000
594000
73°51'0"W
73°52'0"W
595000
596000
Fig. 9 - Map view of Sparkill Creek delta deposit (in yellow and green). The inflection
point in mapped deltaic reflections is indicated by dashed red line. Sediment
isopachs are at 1-meter intervals. Oyster beds in Piermont area are also shown.