NON-ENERGY RESOURCES

RHODE ISLAND COASTAL WATERS

Submitted to

Minerals Management Service

by

The Office of the State Geologist

University of Rhode Island

Department of Geology

Kingston, RI 02881
NON-ENERGY RESOURCES,

RHODE ISLAND COASTAL WATERS

Final Report FY1992

Submitted to

MINERALS MANAGEMENT SERVICE

DEPARTMENT OF THE INTERIOR

COOPERATIVE AGREEMENT NO . 14-3 5-0001-3 073 1 -RI

by

Nasir Hamidzada

Nancy Friedrich Neff

and

J. Allan Cain

Department of Geology

University of Rhode Island

Kingston, Rhode Island 02881

March 1996

J. ALLAN CAIN, RHODE ISLAND STATE GEOLOGIST
ABSTRACT

Operating through the Office of State Geologist, researchers at the University of

Rhode Island have completed a review and assessment of the occurrence, extent, and

accessibility of non-energy mineral resources in Rhode Island coastal waters . Data were

collected over a period of ten years in areas of least user conflict in Block Island and

Rhode Island Sounds. Seismic reflection profiles, side scan sonographs, vibra-cores, and

surficial sediment samples were obtained . Seismic stratigraphic and surficial textural

interpretations were made from the seismic and sonar data. Lithologic, mineralogic, and

textural analyses were performed on core and sediment samples . Results indicate that the

sand and gravel comprising the Pleistocene glacial till, moraine, and outwash deposits of

the Rhode Island offshore area are potential sources of construction aggregate . Selected

areas, most accessible for exploitation, have been mapped . Volumetric estimates range

from 24 million m3 to 2 .1 billion m3. Restrictions on exploitation include use conflicts

with commercial and recreational fishing activities, and shipping traffic .
TABLE OF CONTENTS

PAGE

ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 1

REVIEW OF THE PROGRAM . . . . . . . . . . . . . . . . . . 1

STATEMENT OF THE WORK

Database Procedures . . . . . . . . . . . . . . . . . . . . 4

GIS Map Display . . . . . . . . . . . . . . . . . . . . . 4

ASSESSMENT OF NON-ENERGY RESOURCES

Block Island Sound . . . . . . . . . . . . . . . . . . . . 5

Rhode Island Sound . . . . . . . . . . . . . . . . . . . . 9

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . 12

ll
LIST OF FIGURES

Figure 1 . Non-energy mineral resources, Rhode Island

and Block Island Sounds, RI . . . . . . . . . . . . . . . . . in pocket

LIST OF TABLES

PAGE

Table 1 . List of selected resource areas and summary of data collected

from each area . . . . . . . . . . . . . . . . . . . . . . . . . 3

Table 2 . Summary of the kinds of data analyses carried out in each

of the selected resource areas . . . . . . . . . . . . . . . . . . 3

Table 3 . Characteristics of selected resource areas . . . . . . . . . . . . 6

iii
INTRODUCTION

The Office of State Geologist at the University of Rhode Island commenced a

review of its MMS/AASG Continental Margins program in December 1992. Utilizing

Year 9 funds (FY1991) for the start-up of this review, digital compilation of all the

original Rhode Island MMS data into a Geographic Information System (GIS) was

accomplished. Year 10 funds (FY1992) were utilized to employ the GIS to display and

analyze the data set of sand and gravel deposits . This analysis consisted of 3-dimensional

modeling of bathymetry, integration of bathymetry with side scan sonograph

interpretations, and estimates of resource volumes (where applicable) . Each resource

area has been assessed with respect to physical setting of the area/deposit, quality and

abundance of the resource, and known constraints and restrictions on exploitation .

REVIEW OF THE PROGRAM

For the duration of the MMS/AASG Continental Margins Program, the focus of

the research undertaken by the State of Rhode Island has been the non-energy resource

potential of the coastal offshore . In 1984, as part of the MMS New England Coastal

States Co-operative Program, six vibra-cores were collected and analyzed primarily for

heavy mineral content . Results indicated concentrations of less than 3 .5% (by weight)

(McMaster and Friedrich, 1985) . Significant marine placer deposits were not identified .

In subsequent years, the focus expanded to include evaluation of seafloor

sediment types. Seismic reflection profiles and side scan sonographs were collected from

areas judged to be most accessible and least restrictive with respect to user conflicts .
2

areas judged to be most accessible and least restrictive with respect to user conflicts .

Seismic stratigraphic and surficial textural interpretations were made from the seismic and

sonar data (Neff et al., 1987 and 1988 ; McMaster et al .,, 1991 ; Neff et al, 1992).

Additional vibra-cores and surficial sediment samples, analyzed for grain size and heavy

mineral content, were obtained to further characterize the selected areas (McMaster et

al., 1993 and Neff et al., 1989). Results indicated that significant deposits of sand and

gravel comprised the Pleistocene glacial till, moraine, and outwash deposits and Holocene

marine deposits of the Rhode Island offshore area . As potential sources of construction

aggregate, these deposits were mapped and volumetric estimates were made. Estimates

were made for some areas by determining the thicknesses of suitable deposits from the

distances between acoustic reflectors . In areas where the bottom reflector of the

Pleistocene or Holocene deposit was not discernible on the seismic profiles, an assumed

thickness (based on previous regional investigations) was used . An assumed thickness

was also used in areas in which no seismic data were collected .

Over the course of the evaluation, some selected resource areas were eliminated

from additional consideration on the basis of unfavorable textural results .

Presented in Table 1 is a list of the favorable resource areas and the kinds of data

that were obtained from within each of them . A summary of the analyses carried out in

each area is given in Table 2. All program data has been entered into and is currently

stored in the GIS at the University of Rhode Island .
Table 1 . List of selected resource areas and summary of data

collected from each area. Refer to Figure 1(in pocket)

for survey area locations .

SURVEY

AREA

SEISMIC

REFLECTION

SIDE

SCAN

SONAR

VIBRA

CORE

SURI~'ICIAL

SEDIMENT

SAMPLE

BIS-1 X X X

BIS-2 X X X

BIS-3 X

BIS-4 X X

BIS-5 X X

RIS-2 X X X

-2A X X X

-2B X X X

Table 2. Summary of the kinds of data analyses carried out in each

of the selected resource areas . Refer to Figure 1 for survey area locations .

SURVEY

AREA

GEOLOGIC

ENVIRON OF

DEPOSITION

PARTICLE

SIZE-s u fsce

s.mple

PARTICLE

SIT.E-core

sampk

HEAVY

MINS

DIATOMSISOPACH

MAP

DIGITAL

SIDE SCAN

IMAGE

BIS-1 X X X X

BIS-2 X X X X

BIS-3 X X

BIS4 X X X

BIS-5 X X X X

RIS-2 X X X X

-2A X X

-2B X X
4

STATEMENT OF THE WORK

Database Procedures.

ARC/INFO and Surfer programs were used to carry out 2- and 3-dimensional GIS

data analyses . Surfer was utilized to generate a bathymetric grid of the coastal offshore .

ARC/INFO was employed to create 3-dimensional surface modeling and 3-dimensional

renderings of surficial textural maps, and was also used to calculate the surface area for

each of the resource areas and the volume of the resource deposits within areas BIS-1

and BIS-2. The database which was established during the start-up of this program review

was augmented by the addition of more recent digital bathymetric data with greater datapoint density. Provided by NOAA, the additional data were used to create a more detailed

bathymetry map with a 10 m contour interval .

GIS Man Display.

Figure 1(in pocket) is designed to display 1) a base map of Rhode Island coastal

waters for reference to the specific survey sites, and 2) significant data relative to the

physical setting, and type and abundance of sand and gravel resources .

The base map consists of coastal land areas of Rhode Island (gray) and

bathymetric contours (10 m interval) throughout Block Island and Rhode Island Sounds.

Resource areas BIS-1, BIS-2, BIS-3, BIS-4, BIS-5, RIS-2, RIS-2A, and RIS-2B are

indicated by appropriately labelled boxes. The bathymetry within each of the boxed areas
side of Figure 1 and are overlain by surficial textural data . The intent of these 3-

dimensional models is to illustrate the relationship between grain size and seafloor relief

Also indicated on the base map are vibra-core locations . Lithologic core

descriptions are given in the lower right corner of Figure 1 .

The thicknesses of sand and gravel resources in areas BIS-1 and BIS-2 are

illustrated by means of isopach maps located to the right of the base map . Unit thicknesses

were determined from distances between acoustic reflectors on seismic reflection profiles .

These two areas were the only survey areas in which basement reflectors could be

discerned on the seismic profiles . Therefore, they are the only areas for which isopachs

could be constructed.

ASSESSMENT OF NON-ENERGY RESOURCES

Block Island Sound.

Five survey areas were investigated in Block Island Sound .

Area BIS-1 is located in northwestern Block Island Sound in water depths of 30-

40 m (Fig. I and Table 3) . This potential resource deposit was inferred by Neff et al.

(1987) to consist of Holocene marine sand with patches of gravelly sand . Side scan

observations had suggested that the surface of the deposit was composed of gravel (Neff

et al., 1988). However, core 88-9, intended to sample an inferred relict shoreline feature,

penetrated 1 .65 m of coarse sand overlying medium sand (Neff et al., 1989). The area is

interpreted to vary texturally, both laterally and vertically, from medium sand to gravel .
Table 3 . Characteristics of selected resource areas based on geological data collection and analyses .

Refer to Figure 1 for survey area locations.

DEPTH AREA GENERAL DOWNCORE HEAVY VOLUME USE

(M) (KM2) SURFACE TEXTURE MINERALS ESTIMATE CONFLICTS

TEXTURE (CORE NO.) WT % (M

)

SURVEY (downcore

AREA de th

BIS-1 30 - 40 22 grvl crs sand 4.6 (100cm) 345 million fishing (T),

med sand 4.2 (200 cm) shipping, open

(88-9) ocean

conditions

BIS-2 20 - 50 115 grvl, sand, crs sand, grvl 2.9 (30 cm) 2 .1 billion' fishing,

boulders (88-10) shipping, open

med sand 1 .5 (30 cm)

ocean

conditions,

88-11 0.4 (300 cm tidal currents

BIS-3 17 - 34 18 mixed: fine 77 million fishing,

sand to shipping, open

bould ocean

conditions,

tidal currents

BIS-4 21 - 40 3 mixed: med 25 million fishing (T),

sand to shipping, open

bould ocean

conditions,

tidal currents

BIS-5 18 - 24 9 fine to crs med sand 0.3 (95 cm) 32 million fishing (T),

sand, grvl (84-21) 1 .2 (265 cm) shipping, open

crs sand 3 .4 (60 cm)

ocean

conditions,

84-22 1 .2 (140 cm tidal currents

RIS-2 30 - 40 254 sand, grvl, med sand 0.9 (20 cm) 400 million fishing,

bould. silt 0.3 (220 cm) shipping, open

(88-13) ocean

conditions,

med sand 1 .4 (22 cm) tidal currents

fine sand 0.8 (290 cm)

88-14

-2A 30 - 35 11 sand 24 million

-2B 30 - 35 6 sand, grvl, 84 million

bould

' Calculated by GIS

T: trawl marks observed
7

The intended core target, a possible drowned shoreline feature, can be discerned in the 3-

dimensional bathymetric image of area BIS-1 (Fig . 1) . Sand and gravel patches appear to

lie on the flanks of this positive feature . Core sub-samples yielded heavy mineral values

of approximately 4% (Table 3). The volume of the deposit was initially estimated to be

200 million m3 (Neff et a1., 1988). A more precise digital calculation utilizing the GIS

yielded an estimate of 345 million m3 .

Area BIS-2 is located west of Block Island in 20-50 m water depths (Fig . I and

Table 3) . The appearance of the seafloor in area BIS-2 is irregular due to the hummocky

nature of the underlying Pleistocene glacial moraine deposits, boulder-strewn lag deposits,

and tidal current activity producing large bedforms . Neffet al. (1987) identified over 2

billion m3 of coarse-grained Holocene sediments as potentially suitable for resource

exploitation . Digital calculation by means of the GIS concurred with this estimate (Table

3). Seismic reflection profiles indicated that the thickest accumulation of sediment (30-45

m) comprised a relict flood tidal delta . Core results at this site ( core 88-11) were

consistent with the interpretation of this depositional feature and revealed a well-sorted

medium sand (Neff et al., 1989). Side scan observations indicated that surficial sediments

throughout BIS-2 consisted of patchy sand and gravel with frequent bedform development

and scattered boulders (Neff et al., 1988). Heavy mineral concentrations at core sites

88-10 and 88-11 were found to be less than 3% (Table 3) .

Survey area BIS-3 is located in the northeast portion of Block Island Sound in an

area previously mapped as submerged terminal moraine (Schafer, 1961 ; and Needell et al.,
8

1983) (Fig. 1 and Table 3). Depths range from 17-34 m. Bathymetric contours mimic the

trend of the moraine and create a platform defined roughly by the 20 m contour line . The

seafloor dips more steeply along the east and south sides of this platform . Analysis of side

scan sonographs by Neff et al . (1992) revealed that textural variations were, to some

degree, depth-controlled . The inferred submerged portions of the moraine were found to

be characterized by sand, gravel, and boulders . Surficial units extending into deeper water

along the flanks of the platform reflected a transition from coarse, boulder-strewn

deposits to finer-grained sediments (Fig . 1) . The finest deposits were observed in the

deepest portions of the survey area, in the northeast and southwest corners . Assuming a

regional average for drift thickness of l Om (McMaster et al ., 1991), BIS-3 was estimated

to yield 77 million m3 of sediment (Neff et al., 1992) (Table 3) .

Survey area BIS-4 is located north of Block Island in 21-40 m water depths (Fig . 1

and Table 3) . In earlier assessments (Needell and Lewis, 1984 ; and Friedrich et al., 1986),

this area was found to be characterized by gravelly sand, interpreted to have been

winnowed from coarse-grained, glacial moraine deposits . A high, ranging from 21-25 m

in depth, trends northwest to southeast through the survey area (Fig . 1) . Analyses of

sonographs and surface sediment samples by Neff et al. (1992) and McMaster et al.

(1993) indicated that this high, marked by sand, gravel, and boulders, was a submerged

moraine deposit similar to that observed in area BIS-3 . Percentages of gravel of up to

51 % were found in these sediments . Medium to coarse-grained sand and a patch of gravel

were found to extend into deeper water along the flanks of the high . Based on the
9

regional average drift thickness mentioned above, area BIS-4 was estimated to contain 25

million m3 of sediment (Neff et al ., 1992) (Table 3) .

Area BIS-5 is situated approximately 3 km off the south shore of Rhode Island in

depths of 18-24m (Fig . 1 and Table 3). Inferred relict shoreline features were the intended

core targets at sites AT84-21 and AT84-22. Downcore sediments were found to be

medium and coarse sand, respectively (McMaster and Friedrich, 1985) . Heavy mineral

contents were determined to be <_ 3 .4% (Table 3) . The feature at site AT84-22 is easily

discernible in the 3-dimensional bathymetric model (Fig . 1) . Sonographs revealed that the

surface of this feature was composed of gravel along the apex and fine to coarser-grained

sand along the flanks (Neff et al ., 1992). The remainder of the survey area was found to

be dominated by sand, with numerous irregular gravel patches . Neff et al . (1992)

calculated a volumetric yield of 32 million m3 .

Rhode Islland Sound.

Two survey areas were investigated in Rhode Island Sound .

Area RIS-1 was surveyed seismically but eliminated from further consideration as

a potential resource area after core AT88-12 revealed unsuitable grain size (Fig. 1).

Survey area RIS-2 is located in the middle of Rhode Island Sound, in 30-40m

water depths, covering 135 km2 (Fig. I and Table 3) . Side scan sonographs reveal poorly

sorted, coarse material (gravel, sandy gravel patches, boulders) associated with

Pleistocene glacial till, moraine, and outwash deposits (Neff et al., 1988) . Side scan data

also indicated that recent sand deposits, winnowed from the glacial deposits, occurred in a
10

thin (<3m), patchy veneer over the coarser-grained sediment . Underlying topographic

relief, bed roughness, turbulence, and bottom stress were reported to contribute to the

distribution of these sediments . Neff et al. (1988) estimated that the drift was an average

30 m thick. However, cores AT88-13 and AT88-14 yielded only 2 .5m of medium sand

over finer units (Neff et al., 1989) (Table 3) . The volumetric assessment was reduced

from the initial estimate of 4 billion m3 to 400 million m3 (Table 3) . Heavy mineral

concentrations in cores from RIS-2 were found to be less than 2% .

Two subareas within RIS-2 were examined in greater detail . Area RIS-2A lies to

the north of previously mapped terminal moraine deposits, while RIS-2B lies within the

end moraine (McMaster et al., 1991) (Fig. 1) . Sonographs of the low relief surface in

RIS-2A revealed that the area was dominated by sand (McMaster et al., 1991) and grain

size analyses confirmed this interpretation (McMaster et al., 1993). An estimate of 24

million m3 of suitable sediment was made .

The relief in area RIS-2B was found to be hummocky . Three distinct hills were

observed and sonographs revealed evidence of topographic control over the distribution of

the sediment units (McMaster et al., 1991). As can be seen in the 3-dimensional model in

Figure 1, gravel with boulders dominated on the highs, and sandy gravel to fine sand was

associated with the flanks of the hills . Surficial sediment analyses confirmed the resource

potential of these deposits (McMaster et al ., 1993) and which were estimated to be 84

million m3 in volume (Table 3) .

Both commercial and recreational fishing activities constitute a significant use

conflict in all of the areas surveyed in Block Island and Rhode Island Sounds (Friedrich,
11

1986 and Neffet al., 1993). Trawl marks, indicative of commercial dragging methods,

were noted on sonographs from areas BIS-1, BIS-4, and BIS-5 . Commercial,

recreational, and military vessel traffic, known to frequent the Rhode Island coastal water,

also exist as restrictions on exploitation possibilities . Open ocean conditions and tidal

currents in excess of 2 knots at many of the survey sites exist as impediments to any

marine operations (i .e ., mining) .
12

REFERENCES

Friedrich, N.E., R.L. McMaster, H .F . Thomas, and R.S . Lewis, 1986, Non-energy

resources, Connecticut and Rhode Island coastal waters . Minerals Management

Cooperative Agreement No . 14-12-0001-30115, Final Report, FY 1984, 55p .

McMaster, R.L., and N .E. Friedrich, 1985, Economic minerals of Rhode Island and Block

Island Sounds, Rhode Island. Minerals Management Cooperative Agreement No. 14-12-

0001-30115, Final Report, FY 1983, 74p.

McMaster, R. L ., N.F . Neff, R.S . Lewis, and R . Hyde, 1991, Non-energy

resources, Connecticut and Rhode Island coastal waters . Minerals Management

Cooperative Agreement No. 14-12-0001-30432, Final Report, FY 1988, 48p .

McMaster, R. L ., N . F . Neff, R. S . Lewis, and R . Hyde, 1993, Non-energy

resources, Connecticut and Rhode Island coastal waters . Minerals Management

Cooperative Agreement No . 14-12-0001-30534, Final Report, FY 1990, 38p .

Needell, S . W. and R. S . Lewis, 1984, Geology and structure of Block Island Sound,

Rhode Island and New York . U.S . Geol . Survey Misc . Field Studies, map MF-1621 (4

sheets).

Needell, S. W., C . J . O'Hara, and H . J . Knebel, 1983, Maps showing geology and shallow

structure of western Rhode Island Sound, Rhode Island . U. S . Geol. Survey Misc . Field

Studies, map MF-1537 ( 4 sheets) .

Neff, N. F ., R. S . Lewis, and R . Hyde, 1993, Non-energy resources, Connecticut and

Rhode Island coastal waters . Minerals Management Cooperative Agreement No . 14-12-

0001-30643, Final Report, FY 1991, 86p.

Neff, N. F ., R . L. McMaster, R. S . Lewis, and H . F. Thomas, 1987, Non-energy

resources, Connecticut and Rhode Island coastal waters . Minerals Management

Cooperative Agreement No. 14-12-0001-30296, Final Report, FY 1985, 45p .

Neff, N. F ., R . L . McMaster, R. S . Lewis, and H . F . Thomas, 1988, Non-energy

resources, Connecticut and Rhode Island coastal waters . Minerals Management

Cooperative Agreement No. 14-12-0001-30316, Final Report, FY 1986, 47p.

Neff, N. F ., R . L. McMaster, R. S . Lewis, and H. F . Thomas, 1989, Non-energy

resources, Connecticut and Rhode Island coastal waters . Minerals Management

Cooperative Agreement No. 1412-0001-30387, Final Report, FY 1987, 60p .

Neff, N. F ., R . S . Lewis, R. Hyde, and R. L . McMaster, 1992, Non-energy

resources, Connecticut and Rhode Island coastal waters. Minerals Management

Cooperative Agreement No . 14-12-0001-30497, Final Report, FY 1989, 28p .
13

Schafer, J. P ., 1961, Correlation of end moraines in southern Rhode Island, U. S . Prof.

Paper 424-D, p. D68-70.