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1969 Source of Barrier Island Sediments: Northern Gulf Coast. Hyuck Jae Kwon Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Kwon, Hyuck Jae, "Source of Barrier Island Sediments: Northern Gulf Coast." (1969). LSU Historical Dissertations and Theses. 1672. https://digitalcommons.lsu.edu/gradschool_disstheses/1672

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KWON, Hyuck Jae, 1936- SOURCE OF BARRIER ISLAND SEDIMENTS: NORTHERN GULF COAST.

The Louisiana State University and Agricultural and Mechanical College, Ph.D., 1969 Geology

University Microfilms, Inc., Ann Arbor, Michigan SOURCE OF BARRIER ISLAND SEDIMENTS: NORTHERN GULF COAST

A Dissertation

Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy

in

The Department of Geography and Anthropology

by . Hyuclc Jae Kwon B.A. , Seoul National University, 1960 M.S., Louisiana State University, 1967 August, 1969 PLEASE NOTE:

Not original copy. Several pages have indistinct print. Filmed as received.

UNIVERSITY MICROFILMS ACKNOWLEDGMENTS

This study was sponsored through the Coastal Studies Institute,

Louisiana State University, under Contract Nonr 1575 (.03), Task Order

NR 3SS 002, with the Geography Programs of the Office pf Naval

Research. The assistance and direction of Dr. W. G. Mclntire, major professor, is gratefully acknowledged, and the constructive assistance of Dr. Choule Sonu is appreciated. The encouragement, suggestions, and criticisms of these men have been invaluable during the investi­ gation and preparation of this dissertation. Dr. R. J. Russell re­ viewed the manuscript several times and contributed constructive suggestions. Sincere thanks are given Dr. J. P. Morgan and Dr. S. M.

Gagliano for their guidance during the preparation of the dissertation.

The writer is very grateful to colleagues at the Coastal Studies

Institute for the opportunity to discuss the problems of this study. TABLE OF CONTENTS

Page ACKNOWLEDGMENTS...... ii

TABLE OF CONTENTS...... ■...... iii

TABLES ...... iv

FIGURES...... v

ABSTRACT...... vii

INTRODUCTION ...... 1

Sea Level Rise...... 3 Littoral Drift, Waves, and Tides...... 3

MAGNITUDE OF GULF COAST BARRIERS AND SOURCE OF SEDIMENT. . . . 6

DOWNDRIFT BARRIER ISLANDS...... 7

Santa Rosa Island ...... 7 Mississippi Sound Barrier Islands ...... 15 Bolivar Peninsula ...... 25

INTERDELTAIC BARRIER ARC OF SOUTHEAST TEXAS...... 29

MISSISSIPPI DELTA BARRIER ISLANDS...... 39

Bird-foot Delta Submarine Bars and Barriers ...... 39 Barrier Islands Fronting the Lafourche...... 41 Barrier Islands Fronting the St. Bernard Delta...... 46

BARRIERS OF THE WEST COAST OF THE FLORIDA PENINSULA AND THE APALACHICOLA AREA...... 51

Barrier Islands of the West Coast of the Florida Peninsula ...... 51

Apalachicola Barriers ...... 55

ZERO-ENERGY COAST OF FLORIDA ...... 57

SEDIMENTARY FACIES OF BARRIER ISLANDS...... 61

SUMMARY AND CONCLUSIONS...... * ...... 66

BIBLIOGRAPHY ...... 69

iii Tables

Page

Table 1. Discharge and drainage area'of Gulf coast streams. . 14

iv Figures

Figure Page 1.. Northern Gulf coast: index map, showing barriers and other coastal types...... 5

2. Northern Gulf coast climates' and Gulf of Mexico drift and current sets, with wave-energy levels . . . 5

3. Santa Rosa Island, Red Bluff, and offshore topography...... 8

4. Pleistocene terrace surface near Sea Grove Beach, Florida...... 10

5. Red bluff near Sea Grove Be.ach.'...... 10

6. Mississippi Sound barrier islands ...... 16

7. Cross section of Recent sediments between Beauvoir and Ship Island...... 18

8. Comparative offshore topography of the Alabama coast, Dauphin and Santa Rosa Islands ...... 20

9. Entrance of Mobile Bay...... 22

10. Bolivar Peninsula and the adjacent coast with . cross sections of sediment facies across beaches. . . 26

11. Calcareous nodule and shell fragment beach near the High Island salt d o m e ...... 28

12. Closeup of the calcareous nodules and shell fragments...... 28

13. Interdeltaic barriers and offshore topography near Rockport, Texas...... '...... 30

14. Recent sediments of the continental shelf in a line perpendicular to the coast near Rockport. . 32

15. Recent sediments across Padre island...... 32

16. Broad beach flat and dune ridge of Padre Island, about 15 miles north of the Rio Grande River. 36

v Figure Page 17. Exhumed marsh deposits at the mouth of the Rio Grande River...... 36

IS. Deteriorating Matagorda Peninsula ...... 38

19. Pass Cavallo...... 38

20. Submarine bars around the bird-foot delta of the Mississippi River...... 40

21. Sand spit at South P a s s ...... 42

22. Barrier islands and shoreline changes in the abandoned subdeltas of the Lafourche-Mississippi R i v e r ...... 43

23. Shoreline changes of Isles Dernieres and Timbalier islands ...... 45

24. Sediment facies of delta barrier islands...... 47

25. St. Bernard Delta and the Chandeleur arc...... 48

26. Gulf bottom topography of the Florida west coast and adjacent mainland geology ...... 52

27. Apalachicola barriers and offshore topography .... 56

28. Offshore topography In the zero-renergy coast of Florida...... "...... 58

29. Comparative Gulf bottom topography...... 60

30. Sediment facies of Grand I s l e ...... 62

31. Sediment facies of Galveston Island ...... 64

32. Schematic diagrams of barrier islands...... 67

vi ABSTRACT

The evolution of barrier islands along the northern Gulf coast is

directly related to source of sediments and littoral processes. Since

Johnson formulated his hypothesis on barrier island formation in 1919,

his theory has prevailed for several decades. Johnson's theory results

from consideration of only two dimensions normal to the coastline; a

third, longshore drift, is not regarded as critical for the initiation

of barrier island development. In this study, which is confined to the

northern Gulf coast, major sources of sediment supply and transportation patterns of barrier-forming sand were examined, along with results of

recent oceanographic investigations in the Gulf of Mexico. This study

is based on a comprehensive survey of the literature, maps, and marine

charts, which were correlated with field observations. To obtain a perspective, only gross forms and processes of barrier development w ere

considered.

Evidence indicates that Santa Rosa Island and Mississippi Sound

and Bolivar Peninsula barriers developed downdrift of sediment-supplying

coasts of Quaternary age. These barriers evolved with the rise of sea

level to its present stand. Apalachicola barriers formed on the flanks

of the Pleistocene deltaic plain. Coasts such as the 'Stretch between

Destin and Panama City, Florida, and the zero-energy coast of Florida

do not have barrier islands. In these cases the modern shoreline is

abutted against Pleistocene deposits which supply the local source of

sediments.

The concave-seaward arc of the Texas barrier islands between the

deltas of the Rio Grande and Colorado-Brazos rivers evolved upward with

sea level rise. The barrier arc development was initiated either from

vii mainland beaches or from incipient or existing barrier complexes.

These major rivers must have contributed the bulk of barrier island sediments through the converging drift sets between the two deltas.

Barrier islands around the Mississippi Delta have developed as bay-mouth barriers on the flanks and against abandoned natural levees and distributary mouth bars of the subdeltas. The Chandeleur arc, a convex-seaward chain of islands, represents an advanced stage of bay-mouth barrier development around an older delta lobe. The arc is maintained by sediments accumulated through shoreline regression against the existing barrier and submerged deltaic deposits.

Besides the upcurrent coastal sources of Pleistocene material and the above-mentioned rivers, large estuaries such as Mobile and Matagorda bays also supply sediment to the barrier beaches. In all cases, lit­ toral drift is the primary factor in transporting barrier-forming sands from the source and initiating or sustaining barrier island development in the northern Gulf coast.

viii INTRODUCTION

In the field of coastal geomorphology, the Gulf coast is world famous for the development of barrier islands, which are depositional landforms that border more than half the coastline from the mouth of the

Rio Grande River to the west coast of Florida (Fig. 1). During the past several decades, numerous studies of Gulf coast barriers have accumulated a great deal of information on barrier island morphology, sedimentology, and associated processes.

The following publications constitute important contributions in the Gulf coast: Price’s pioneering work. Role of Diastrophism in

Topography of Corpus Christi, South Texas (1933) , in which development of Recent and Pleistocene barriers was interpreted; Russell's discussion on development of barrier islands along submerged coasts (1936); Bullard' analytical study of the source of beach sands in the Texas coast (1942);

Lohse's treatise on sediment source and movement alongshore in the southwestern Texas coast (1955); Fisk’s sedimentologicai studies of

Grand Isle (1955) and Padre Island (1959); studies on the overall Texas coast by LeBlanc and Hodgson (1959) and Bernard and LeBlanc (1965); and

Shepard’s descriptive discussion on barriers of the entire Gulf coast

(1960). Much of the important work refers to the Tekas coast, which is most notable for barrier development along the northern Gulf coast.

When the basic theory of barrier formation is considered, opinions are diversified. The most important question, where the barrier-forming sands come from, has been debated for more than a century, likely beginning with de Beaumont (1845). Since the publication of

Johnson's Shore Processes and Shoreline Development in 1919, the pre­ vailing hypothesis has been that the bulk of barrier sands are derived from offshore. Barrier islands were postulated as an emerged landform from the sea bottom. This hypothesis has partly been a product of consideration of only two dimensions normal to the coast, on the basis of offshore profiles. Littoral drift is not generally regarded as critical for the initiation of barrier island development. Most coastal investigators have considered littoral drift as an important beach pro­ cess after the formation of a barrier island.

It is the purpose of this paper to investigate major sources and transportation patterns of barrier-forming sands along the northern

Gulf coast and to ascertain possible reasons for barrier formation and for the absence of barrier islands in some sections of the Gulf coast. The author considered the geomorphological, geological, and sedimentological characteristics along the coast laterally as well as normal to the coast. • This paper is primarily a descriptive treatment, and only gross form-process relationships are considered. Emphasis was placed on a conceptual model or working hypothesis for further field study.

Because the mode of development in every barrier island is different, depending on the sediment sources, coastal configuration, offshore slope, and drift patterns, those considered in this study are dealt with individually; but certain barriers, which appear to have some common aspects, are grouped together.

The author made a comprehensive survey of the literature, maps, marine charts, and air photos; he also made several'field trips along the Texas coast to the mouth of the Rio Grande River and the coast between the Mississippi and the Apalachicola deltas. Observations of the general surface morphology of barrier islands and coastal geology were made. Most of the information, however, came from written records or other first-hand sources. An attempt is made to.reevaluate the information on barrier islands and to give a reasonable interpreta­ tion for their development, which, is yet an unsolved and controversial subject in coastal geomorphology.

Sea Level Rise

Barrier development cannot be properly interpreted without an understanding of the nature of the late post-glacial sea level rise.

Many investigations on this problem have been made in the Gulf coast area (Gould and McFarlan, 1959; Curray, 1960; Shepard, 1960; Coleman and Smith, 1964; Scholl and Stuiver, 1965). To avoid confusion in the discussion, the author'follows the near stillstand of sea level concept. It is generally accepted that sea level rose at an average rate of about 2.8 feet per century from 17,000 to 8,000 years B.P.

(Shepard, 1960). At the end of this period the sea stood approximately

29 feet lower than at present CColeman and Smith, 1964). Prior to

6,000 years B.P., when sea level was about 20 feet lower than today

(Russell, 1967), the rate of rise decreased noticeably to less than

1 foot per century, and about 3,600 years ago its position had reached nearly its present level (Coleman and Smith, 1964). It is pointed out that no evidence exists for a sea level stand above its present position during Recent times.

Littoral Drift, Waves, and Tides

Littoral drift and waves play a very important role in forma­ tion of barrier Islands. The longshore drift pattern shown in

Figure 2 is frcm various sources which are discussed in the text.

The ocean currents and wave energy levels in the same figure are after Leipper (1954) and Price (1954b), respectively. The Gulf coast has a small tidal range, averaging at most places not more than a foot or two. Mixed, semidiurnal tides on the west coast of the

Florida peninsula gradually change to diurnal tides along the northern

Florida coast and toward the Texas coast, .(Mariner, 1954). In the northern Gulf area, which has low tidal ranges, wind has a marked effect on changing water levels. Hurricanes have been known to raise the levels to more than 20 feet above sea level at the Gulf shore and above 10 feet in the large bays or estuaries (U.S. Army Corps of

Engineers, 1958). 5

LOUISIANA F"1 Q ..

TEXAS VJ5.

lOti'FLORIDA'if »00 Fo*h®ml * -

Toxas Barrier Mississippi S. I. Arc I. Santa Rosa I. Matagorda P. St. Jo sep h Spit 26° Galvoston I. Apalachicola I. Bolivar P. Anciote Keys ChandoUur I. Sanibel. I.

94° 90° 86 ° 82"

Fig. 1. Northern Gulf coast: index map showing barriers and other coastal types.

^76347^577

30°

90° 86 ° 82°

Fig. 2. Northern Gulf coast climates and Gulf of Mexico drift and current sets, with wave-energy levels H (high), M (moderate), L (low), and 0 (zero). Climates after Thornthwaite (1948), wave-energy levels after Price (1954b), and ocean currents after Leipper (1954). 1, semiarid; 2, dry subhumid; 3, moist subhumid; 4, humid B^; 5, humid B£> MAGNITUDE OF GULF COAST BARRIERS AND SOURCE OF SEDIMENT

Coastal barrier islatids, which border more than half the shore­ line of the northern Gulf of Mexico, vary considerably in both length and width. The most extensive barriers have developed as huge concave-seaward arcs along the southwestern Texas coast between the deltas of the Rio Grande and the Colorado-Brazos rivers (Fig. 1).

These rivers flow directly into the Gulf through their deltas, while most other Gulf coast streams (except the Mississippi and some small rivers of Florida) empty into bays or estuaries. The Texas barrier arc stretches for nearly 245 miles along the coast, and locally may exceed 2 miles in width. The materials that comprise the barriers are mostly terrigenous sands. Most of the sediment along the south­ western Texas coast initially reached the Gulf by streams.

The Rio Grande and Colorado-Brazos rivers have likely been supplying sediment directly into the Gulf throughout Quaternary or earlier times. Beaumont formation of Pleistocene age exposed along the beach on the southwestern side of the Colorado-Brazos Delta and the reported occurrence of Pleistocene deltaic material in the nearshore Gulf bottom off the Rio Grande Delta (Rusnalc, 1960) sug­ gest that the above river deltas do not represent alluviation of large inundated river mouths or estuaries during the near stillstand of the sea. The magnitude of the Texas barrier arc appears to be related to the source of sediments at both ends.

Bolivar Peninsula, Mississippi Sound barriers, and Santa Rosa

Island occur downdrift of long, straight coasts which have no barrier islands. The magnitude of these barriers is proportional to the stretch of the upcurrent coasts without barriers. Cuspate barriers of the Florida panhandle have developed on the flanks of the Pleisto­ cene delta of the Apalachicola River.

The vest coast of peninsular Florida has nearly continuous barriers, with some intervening mainland beaches, from Anclote Keys to Sanibel Island (Fig. 1), but the barriers are small and are close to the mainland•shore. The Florida peninsula.has no significant rivers, and surface drainage of a flat karst topography is locally absent. The mainland has delivered a minimum of detrital sediments to the coasts. Barrier beaches along this section contain high shell content (Martens, 1931), and coquinas frequently crop out along the modern shores.

Barrier islands around the Mississippi Delta cannot simply be correlated to a certain source because of the dynamic characteristics of delta development.

DOWNDRIFT BARRIER ISLANDS

Barriers grouped here have westwardly drift sets along the beaches. They are either spits, like Bolivar Peninsula, which is attached to the mainland at one end, or classical types of barrier islands, like Santa Rosa Island and the Mississippi Sound barriers, which are completely separated from the adjacent coast. In all cases the adjacent coasts updrift of the barriers are long and relatively straight but do not have barrier islands.

Santa Rosa Island

Santa Rosa Island is a narrow barrier island of medium-grained white sand. It has a long, unbroken beach, extending nearly 52 miles in length. This island is almost parallel to the Pleistocene main­ land coast between Destin and Pensacola (Fig. 3, inset). Behind the 40.

'70 60 7 0 70 70

80 70 80 '8 0 ' 7 0 8 0 7 0

8 0 8 0 ■70 .8 0 '

.7 0

8 0

8 0 , .90 • - ->i... ; - v-fP n n a m a Pen* a col a-il? 100 '-Mobile *xlBa>2 MAP AREA 100

Fig. 3. Santa Rosa Island, Red Bluff, and offshore topography. Gulf bottom contours after Hyne and Goodell (1967).

CO island is Santa Rosa Sound, a continuous lagoon tapering in width

from 2 miles near the western end to less than a quarter-mile east­ ward. The lagoon is connected to bays at both ends.

Extending eastward from Santa Rosa Island to near Panama City,

a distance of approximately 50 miles, the beach juts up against the mainland, and barriers have not formed. A Pleistocene sandy terrace, ranging in height from 20 to 30 feet faces the Gulf, and a narrow

Recent beach abuts the bluff (Figs. 4 and 5). Old navigation charts show the name "Red Bluff" along this coast, x/hich is descriptive of the color of oxidised sand occasionally exposed in the bluff face.

In places small lakes have formed xdhere minor entrenched drainage gullies have been inundated.

Along the entire shore from the xtfestern end of Santa Rosa Island to near Panama City, the shoreface,* x^hich is the steep and smooth surface sloping doxm from the beach to the inner continental shelf, is very steep— 50 to 60 feet per mile (Fig. 3). Beyond this steep shoreface is the extensive, almost flat inner continental shelf, which has a regional gradient of about 3 to 4 feet per mile. Its surface is highly irregular, consisting of ridges and troughs which exhibit a maximum relief in excess of 30 feet. According to Hyne and

Goodell (1967), these features are not an active form, and the sur­ face materials are composed of light broxxm-to-gray mottled quartz sand xtfith varying amounts of molluslt and echinoid fragments. Hyne

*Russell (1968) defines shoreface as "the narrox? zone, always submerged, seaxxrard from the loxtf-tide shoreline over which bed materials are entrained and transported." In this paper, shoreface, a product of wave action, refers to the steep submarine surface that descends to the gentle inner continental shelf. Usually the break batxreen the tx\To slopes occurs gradually in this study area. 10

Fig. 4. Pleistocene terrace surface near Sea Grove Beach, Florida. It stands about 30 feet above sea level. See Figure 3(inset) for the location of Sea Grove Beach.

mr,,

Fig. 5* Red Bluff near Sea Grove Beach. Notice the vegetation cover on the bluff face and a low dune ridge in front of the bluff. and Goodell suggest that fluvial action when seas were lower incised the ridge and trough topography. Subsequent sea level rise modified the topography to its present form. ' This pattern of relict shelf morphology extends between Mobile Bay and Panama City. Price (1954b) mapped this Gulf bottom as an "unfilled entrenched valley." Dietz

(1963) also shows detailed topographic forms of the shelf off Panama

City. A smooth and steep shoreface extends to a depth of 40 feet, but greater depths are marked by incised, relict topography. Dietz men­ tions a well-known submerged forest on the relict surface, which verifies its subaerial existence.

The above information indicates that beach development was not significant during the post-glacial transgression of the sea across this portion of the flat inner continental shelf. As Mclntire sug­ gests, it is not necessary to believe that eusuatic sea level rise velocities exceeded rates which would prohibit beach formation (Ho and Mclntire, in press). The preservation of subaerial topography in the sea bottom here may be interpreted partly in terms of the small regional gradient, 3 to 4 feet per mile, which does not allow sig­ nificant wave action to form beaches (Keulegan and Krumbein, 1949).

Minor amounts of sediment from rivers along the adjacent coast may also be a contributing factor. It is possible that this section of the coast may have experienced conditions similar to the zero-energy coast of Florida, when sea level was lower.

Wave action likely began to develop beaches when the sea started to drown the steep shoreface near the 50- to 60-foot con­ tour line during sea level rise. No geomorphic evidence suggests that the mainland coasts from Pensacola to Panama City originally descended to the Gulf bottom with the same slope as characterizes their land surface, as Johnson's barrier-island profiles postulate.

That the mainland coasts, which seem to have formed as coastal barriers during the previous interglacial periods, preserved their shorefaces fairly well because of lack of stream dissection in the narrow coastal strips is highly probable.

The Red Bluff indicates extensive coastal erosion, but the charts do not show any corresponding wave-built terrace on the sea bottom. The classical concept of the xjave-built terrace should be examined thoroughly. The writer suggests that the Red Bluff coast does not.form barrier islands because the eroded material is trans­ ported westwardly by littoral drift to construct Santa Rosa Island.

It should be noted again that the Red Bluff is not a single headland but a nearly 50-mile-long straight coast with soft rock. The shore­ face of the Red Bluff coast is an erosional surface, but that of

Santa Rosa Island is depositfonal in nature.

In addition to the Red Bluff coast, Choctawhatchee Bay (Fig* 3) should be considered as another possible source of Santa Rosa Island sediment, because estuaries are known to supply a considerable amount of sediment seaward under favorable conditions (Lohse, 1955; Mclntire and Morgan, 1962). The bay bottom is broad and flat-floored, lying deeper than the sand ridge across the bay mouth between Destin and the opposite Pleistocene terrace. Depth of the bay floor is over

9 30 feet. In contrast, the tidal inlet connecting the bay and the

Gulf at the eastern side of Santa Rosa Island is very narrow and shoal. The ship channel through this inlet has to be maintained by periodic dredging because of continuing, sediment drift from the Red . Bluff. It might be anticipated that tidal exchange between Lae Culf and the large tidal storage area of .Choctawhatchee Bay would be more than adequate to keep this pass scoured, but this is not the case.

Choctawhatchee Bay is virtually sealed by a sand ridge across the bay mouth.

The location of the inlet at the extreme eastern side of the' bay is another indication that little tidal exchange occurs through the inlet. Otherwise, the pass would have migrated westwardly, and the sill would have been scoured by a deeper channel.

Old charts (1844) show the eastern end of Santa Rosa Island extending about 1 mile eastward of its present position and overlap­ ping and offset from Moreno Point. The island and the point were separated by a narrow tidal pass at that time. According to Martens

(1931), however, the present inlet was breached as the result of a flood on the Choctawhatchee River in 1928, and the old inlet which hugged the western end of Moreno Point was subsequently closed.

The Choctawhatchee Bay has a small drainage area and normally carries little discharge (Table 1). As in the case of the'1928 flood, however, abnormal rainfalls associated with Gulf squalls or hurricanes increase discharge significantly. On such occasions sediment discharged from the bay through the tidal inlet and into the Gulf may be considerable. Such processes may have been an impor­ tant contributing factor to development of the large submarine bulge fronting Santa Rosa Island at a depth of 30 to 60 feet (Fig. 3). At any rate, this bulge is certainly a depositional form associated with the bay.

At present Santa Rosa Island appears to be eroding ill some 14

Average Dis­ Drainage Area Stream charge, cfs. sq. mile Station & Bay Period

Rio Granc j 3,984 182,215 Brownsville 1934-50 Gulf of Mexico Nueces 877 16,660 Nathis 1939-59 Nueces Bay San Antonio 526 3,918 Goliad 1924-29 S. A. Bay 1939-59 Colorado 2,135 41,650 Bay City 1948-59 Gulf of Mexico Brazos 4,890 44,100 Juliff 1949-59 Gulf of Mexico Trinity 7,389 17,192 Romayor 1924-59 Galveston Bay Neches 6,260 7,923 Evadale 1904-06 Sabine Lake 1923-59 Sabine 8,844 9,440 Ruliff 1924-59 Sabine Lake Mississippi 558,900 1,144,500 Vicksburg 1928-59 Gulf of Mexico • Pearl 8,818 6,630 Bogalusa 1938-59 Lake Borgne Bogue Chitto 1,867 1,210 Bush 1937-59 Miss. Sound Pascagoula 9,417 6,600 Merrill 1930-59 Miss. Sound Tombigbee 11,330 8’, 700 Gainsville 1938-59 ' Mobile Bay Alabama 31,230 22,000 Claiborne 1930-59 Mobile Bay Perdido 753 394 Barrineau 1941-59 Perdido Bay Escambia . 5,989 3,817 Century 1934-59 Pensacola Bay Yellow 1,041 474 Crestview 1938-59 Pensacola Bay Cho ctawhat chee 6,922 4,384 Bruce 1930-59 Choctaw. Bay Apalachicola 21,160 17,100 Chattahoochee 1928-59 Apalach. Bay Ochloclconee 1,614 1,660 Bloxham 1926-59 Apalachee Bay Suwannee 6,350 7,090 Branford 1931-59 Gulf of Mexico Withlacoochee 1,491 2,220 Pinetta 1931-59 Gulf of Mexico Peace 1,281 1,370 Arcadia 1939-59 Charlotte H.

Table 1. Discharge and drainage area of the C'ulf coast streams. After the U.S.G.S. Water Supply Paper 1623 and 1632. sections, as suggested by exhumed peat at low tide along the beach

near the western end. In places dunes are presently being eroded.

Apparently the barrier receives less sediment from the source area

now than in the past. Near the time of the relative stillstand the

sediment-supplying coast to the east is believed to have experienced

this sequence of events: the long, straight shoreline composed of

unconsolidated materials became simplified rapidly through straighten­

ing of the shoreface, and the supply of sand into the littoral zone,

abundant in the beginning, gradually decreased. The Red Bluff, bor­

dered seaward by a low, continuous dune ridge and covered with vege­

tation, likely indicates the stabilization of the coast (Rig. 5).

The author believes that Russell's hypothesis (1967) holds true also

for barrier beaches:

As long as the last major rise of sea level was taking place, new areas' of coastal plain were being inundated and fresh supplies of sediment were encountered,... Beach volume increased as long as the rise of sea level continued, the surplus sand was blown downwind to form coastal dunes. The beach-dune system reached greatest volume as stillstand was approac ied. But once that level was attained, new sediment supplies were no longer encountered and marine processes brought about a net loss to the system.

Zenkovich (1964, 1967) etpressed the same opinion: that long still­ stand of the sea is unfavorable for continuous sediment supply.

Mississippi Sound Barrier Islands

The Mississippi Sound barriers consist of five islands parallel to the Pleistocene mainland coast. Dauphin Island is at the mouth of Mobile Bay, and westward are Petit Bois, Horn, Ship, and Cat islands (Fig. 6). The sound behind the islands is very wide, more than 7 miles on the average, and deepens gradually from mainland shore to the islands, exceeding 20 feet locally. Longshore currents carry sand from east to west along the barrier beaches (Priddy et al., t C &.G-S C hart No 1 U»9

fra*** 8 7 ? 50

JjVfcnd /yn ■

•41 7 »t * Kt . f it %JL: . « r*{ 7 31 ** « c*ntaiowet3ini7M l^‘}J *» . — . II 51 » • / ^ A

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V?«p f/9S9l

frntr**C6B) * •* Kvtkl

13 II

12 II 13 u tr*S » S T* * • r ’• .. ... « *'**’ * 50 ' 19 l^CbxrtJ22n «A»A- " ■ 13 ,» »» >3 o>K>faUft.

Fig. 6. Mississippi Sound barrier islands. The convex-seaward chain of islands immediately east of North Island is the Chandeleurs. Depth in fathoms. From the U.S.C.G.S. Chart 1116. 1960; Foxworth ojt _nl., 1962).

According to Rainwater’s diagram of Recent sediments in the sound between Beauvoir and Ship Island (Fig. 7), the sound deposits are underlain by prc-transgressive floodplain alluvium, which in turn is underlain by oxidized Pleistocene materials. The sound deposits cease landward of the island, but the subaerially deposited alluvium extends beneath the barrier sand. Its extension beyond the barrier island is unknown. Curray and Moore (1963) report exten­ sive "basal sands" in the Gulf bottom off the Mississippi barriers, xtfhich are the littoral sands of the rising sea. Consequently, the former subaerial surface has been buried beneath the sands, and the topography of the inner continental shelf west of Mobile Bay is very smooth. The Alabama and Tombigbee rivers, which drain into Mobile

Bay, together constitute the largest river system on the Gulf coast east of the Mississippi River (Table 1). These rivers must have been contributing sediment to the Gulf through Quaternary times.

Luawick (1963) found that the barrier sands locally overlie marine clays, which in turn overlie weathered Pleistocene clays. A piece of wood collected at the contact with the weathered zone gave a C-14 date of 5,000 i 300 years B.P. Ludwiclc believes that the barrier sands were deposited on the coastal muds as a result of spit-building from headlands. He does not, however, mention the exact location and characteristics of the sample or any specific headland. Shepard (1960) expressed more specifically his view about the source of the barrier sands:

For some barriers, there appears to be no good land source of sand. For example, the Mississippi islands have no nearby bluffs to supply the sediments, and the chief river source enters the head of the lengthy Mobile Bay. SHIP ISLAND

Barr!or sandi;

A lluvium

Ploiilocono

14 MILES

Fig. 7 Cross section of Recent sediments bet ween Beauvoir and Ship Island. See Figure 6 for the location of cross section. Modi­ fied after Rainwater(l964) • Transportation of sand across the long muddy stretches of the bay seems unlikely, although a little sand may move along the bay shore.... The easterly winds and currents are carrying the sand from the present islands to the west. Therefore, unless there is an eastern source, the sand should give out on the eastern side, but the maps of the past 100 years do not show a net loss.... The only sand available seems to be from the continental shelf. The presence of a mud zone outside the islands and a mud-filled trench along part of. the island front ... apparently indi­ cates that the shelf source is east of Mobile Bay where, according to the chart, sand appears to be continuous out from the shore over the shoal bottom. Thus, the evidence from the Mississippi islands favors an offshore source, but also indicates the importance of longshore drift.

Although the continental shelf east of Mobile Bay has abundant

sandy materials (Upshaw et al., 1966), the shelf consists of relict

topography like that along the section of Santa Rosa Island (Price,

1954b). Toward the present beach, however, there exist extraordi­ narily broad shoals in front of the entire coast from Mobile Point

to Pensacola (Fig. 8 A). The 30-foot contour zigzags, and its pat­

tern appears like fingers protruding’to the Gulf. The contour

delineates probably a subaerially originated relict feature. The

steep shoreface has its base at a depth of about 18 feet on the

chart. On either side of this coast— that is, in the Mississippi

barriers and Santa Rosa Island— the 30-foot contour continues along

the barrier island shoreface in a smooth line (Fig. 8 B and C).

The entire coast from near Mobile Point to Pensacola or between the

above two barrier systems forms a gigantic topographic bulge toward

the Gulf. Barrier islands of Mississippi Sound have developed down-

drift of this coast.

Mobile Point is an extension of a Pleistocene spit (Fig. 8 A).

The rolling Pleistocene surface extends halfway along the entire spit.

Although Recent beaches and some lagoons have developed along the m z m . Ploistocono

^ ° fc il o *' p* LITTLE LAGOON

.30 ■30 “30

MILES CONTOURS IN FEET

MISSISSIPPISOUND Pleistocene ■DAUPHIN ISLAND SANTA ROSA SOUND

SANTA ROSA ISLAND 30 fi m invsswt ■30 \MOBILE. y .B A Y ^ :: P'dns'a'cdld

‘60

MILES MILES 60 GULF OF MEXICO CONTOURS IN FEET CONTOURS IN FEET 60 **

Fig. 8. Comparative offshore topography of the Alabama coast, Dauphin and Santa Rosa islands. Gulf bottom contours after the U.S.C.G.S. Chart 1265 and 1266. coast between near Mobile Point and Pensacola, Recent deposits are

very narrow and probably are shallowly perched on Pleistocene material,

as the offshore contours suggest. Bluffs do not exist along this

coast, but the presence of bluffs is not the only criterion that

suggests that sediments are derived from along coasts, as will be

discussed in connection with the development of Bolivar Peninsula.

• The extensive shoals composed of soft and unconsolidated sands and

the shallowly based shoreface are indications that this coast may

have supplied sands to the west across Mobile Entrance when sea level

was approaching its present position and that it is also supplying

them at present. As far as the author is aware, there is no mechanism

understood which sweeps sands toward the beach from the continental

shelf beyond the shoreface.*

According to old charts, Mobile Entrance (Pig. 9) is nearly

stable. Sand bypassing across an inlet from the upcurrent coast

follows the "outer bar" (Bruun et_'al. , 1959)., Pelican and Sand

islands (Fig. 9 C and D) are small subaerial features based on such

an outer bar that has a base about 7 miles long and extends nearly

4 miles into the Gulf. These islands have changed much in shape

with time. The outer bar consists of well-sorted coarse sand, while

*Beach Erosion Board (1950) made a test of beach nourishment at Long Branch, New Jersey. Dredged material from New York Harbor entrance channels was dumped in a ridge about 7 feet high, 3,700 feet long, and 750 feet wide, in 38 feet of water (mean low water), about one-half mile offshore. Over the period October 1948 through October 1949 the stockpile remained in place or increased slightly in quan­ tity, while the beach in the vicinity showed marked erosion. Although the material showed movement by wave action, it did not move contin­ uously in any one direction, but haphazardly. Norris (1964) reports that a 5-foot-high and 2,100-foot-long ridge in about 22 feet of water, 1,000 feet offshore, which w'as piled with the dredged material from the harbor of Santa Barbara, California, remains essentially infact after a lapse of 25 years. Cha rt 1266Fig. 9 Entrance of tfobile Bay. Depth in feet. From the U.S.C.G Chart 1266Fig.

N> to the floor of Mobile Bay is covered by mud (Upshaxtf et_ al., 1966).

Evidence shows that Mobile 3ay, as x

barrier coast, supplies sediment to the Mississippi barriers. The

mean tidal range in Mobile Bay is less than 2 feet, but the large

gunstoclc-shaped bay and fresh x^ater discharge into it maintain active

exchange of Xvfater through the inlet. As a result, a channel over

40 to 50 feet deep is maintained in the pass. The massive semicircular

outer bar.is a depositional form associated with water exchange in and

out of the bay. Mobile Bay is very shalloxvf, for the most part less

than 10 feet, but a basin more than 15 feec below x^ater level has been

scoured behind Mobile Entrance by the predominant ebb tide in combi­

nation xtfith river discharge. Otherx^ise, an "inner bar" or tidal

delta xtfould have formed in the bay (Bro\\m, 1928). The size and depth

of the scoured basin are stable, according to comparison of old and

nexcr charts.

The mean range of tide in the bay is small normally, but it is

not uncommon for large quantities of Gulf water to be blox-zn into the

bay during tropical storms and hurricanes, \vfaich are knoxm to raise

water levels in the bay up to 8 feet (Wilson, 1951). If subsequent

draining of water from the bay is coincident with river flooding,

velocities capable of flushing sediment into the Gulf are reached.

The bay bottom, which is mud-covered under normal conditions, should

not be considered as good evidence that coarse material is not trans­

ported into the Gulf. According to Wilson (1951), most of the nearly

80-mile-long bay shore is characterised by unconsolidated sandy bluffs, averaging about 10 feet in elevation, which are attacked by waves, especially during hurricane and storm tides. The eroded material may be moved toward the bay bottom to be flushed gulfward,

or may be deposited along the bay shore and under the right current

conditions may be flushed into the Gulf. Air photos show littoral

drift along the western shore of the bay and sediment-laden currents emptying into Mississippi Sound through the shoal water between Cedar

Point on the mainland shore and Little Dauphin Island (Fig. 9 A and B).

Rapid sedimentation at the eastern end of the sound formed the shoals, which are unusually, shallow compared with the rest of the sound. The contribution of bay sediments will be discussed further in connection with the development of Matagorda Island, Texas.

It is uncertain whether the Mississippi barriers were formed by spit growth since sea level reached stillstand (Ludwick, 1963) or evolved upward with, the rising sea. The reported basal sand in the

Gulf bottom (Curray and Moore, 1963) and the fact of no significant open neritic sediments in the sound bottom where sound deposits overlie the floodplain alluvium (Rainwater, 1964), however, may together con­ stitute evidence for the continuous existence of barrier beaches during post-glacial rise of the sea. It is certain that the barrier islands were existent before the development of St. Bernard Delta of the

Mississippi River, which was active between about 2,800 to 1,700 years before present (Kolb and Van Lopik, 1966). The Chandeleur

Islands (Fig. 6) represent approximately the delta margin. The north-south, spit of Cat Island, which, is a result of the erosion of the eastern extremity, probably began to form when the St. Bernard lolta deflected the east-to-west currents southward.

The Mississippi barrier islands are changing rapidly in their lateral position. The islands are constantly undergoing erosion at eastern ends and deposition at western extremities, and thus appear

to migrate to the west with time. They have remained approximately at the same distance from the mainland shore during the past several hundred years. It seems that the islands represent the top of a formerly more continuous barrier island chain. Today the islands are separated by wide tidal inlets. An old map dated 1752 (Richmond,

1962) presents only four islands instead of the present five: Isle

Dauphine, Isle a Corne, Isle aux Vaiffaux, and Isle aux Chats. If we assume as valid the concept of diminishing sediment available from the sediment source along a coast with a standing sea level, which was suggested earlier, the decreasing amount of sediment from the major source coast between near Mobile Point and Pensacola will allow a retreat or segmentation of the downdrift barrier islands.

Bolivar Peninsula

Bolivar Peninsula, Texas, is a sand spit approximately 17 miles long which is attached' to the mainland at its northeastern end, and together with Galveston Island fronts Galveston Bay (Fig.

10). The peninsula has distinguishable recurved beach ridges fronted by a later series of beach ridges paralleling the shore. •

The mainland coast between Bolivar Peninsula and Sabine Pass experiences coastal erosion. LeBlanc and Hodgson (1959) report that segments of Texas Highway 87 have been relocated a number of times during the past 20 years and that the shoreline has probably receded several thousand feet during the past few thousand years.

Unpublished data of the Coastal Studies Institute show that this retreating mainland shore comprises a thin veneer of Recent marsh and beach deposits overlying the Pleistocene surface. The Beaumont ✓High I s I a n d *>*-*

OAIVESTON ISLAND 10 MILES GULF OF MEXICO Chem er

CONTOURS IN FEET Beach ridge

- 0 FEET Mud ;;.;;v••••• v * sondi t

v>%Plci$tocen e />yy£ Foreshore W/////////////ZM, Foreshore m z z m F / z v z /yJPloislo/{Pleislo cene^!cene% I I I I '4Z± 200 400 FEET 200 400 FEET 0 200 400 FEET 0 200 400 FEET 200 400 FEET

Fig. 10. Bolivar Peninsula and the adjacent coast with cross sections of sediment facies across beaches. The cross sections after unpublished data of the Coastal Studies Institute.

ro o formation of Pleistocene age at cross sections C and D in Figure 10

occurs at a depth of less than 10 feet below sea level. Toward

Bolivar Peninsula the depth of the Recent-Pleistocene contact

increases appreciably. West of section A (Fig. 10) a boring which was terminated at 60 feet was still in Recent deposits. The sedi­ mentary sequence of foreshore deposits near the bottom of sections

A and B indicates the growth of Bolivar Peninsula. The Recent-

Pleistocene contact eastward from High Island lies at shallow depths, but near Sabine Pass it deepens into the Pleistocene entrenched valley of the Sabina River. Here it lies more than 100 feet below sea level (Kane, 1959). Beach ridges on the flanks of Sabine Pass are Recent in age and indicate accretion at the river mouth.

Shepard (1960) considered the shallow offshore bottom and the

Mississippi River the source of the peninsula sands. It Is more likely that the material was derived from the retreating shoreface of the mainland coast and the nearby Sabine River. The steep shore­ face along the coast between Bolivar Peninsula and Sabine Pass

descends to a depth of more than 20 feet, with a slope of about

17 feet per mile and a width of about two-thirds of a mile. It gradually merges to the gentle inner continental shelf. Cobble-sized

calcareous nodules and shells constituting the beach near the High

Island salt dome, in a coast of low-energy waves, are suggestive of the sediment source (.Figs. 11 and 12). The Beaumont formation includes blue-yellow calcareous clays, brown sands, oyster beds, and considerable quantities' of calcareous nodules irregularly dis­

tributed (Hayes and Kennedy, 1903; Duessen, 1924).

According to Mclntire (oral communication), prolonged, strong 28

B*-'V

- Fig. 11. Calcareous nodule and shell fragment beach near the High Island salt dome.

- Fig. 12. Closeup of the calcareous nodules and shell fragments. winds from the Gulf are effective in raising the water level of

Sabine Lake. Coincident with high river discharge, the subsequent draining of the water attains sufficient velocities to entrain and transport materials from the lake to the Gulf, as in Mobile Bay.

The Sabine River, together with the Neelies (Table 1), is partly responsible for.the formation of accretional topography at the mouth of the pass and may contribute sediment to the peninsula by the predominant westerly longshore currents.

INTERDELTAIC BARRIER. ARC OF SOUTHEAST TEXAS

The Rio Grande and Colorado-Brazos rivers have built deltaic plains directly into the Gulf of Mexico, vrhile most other Gulf coast rivers flow into estuaries. A concave-seaward barrier arc which extends about 245 miles parallel to the mainland shore has developed between these two deltaic plains.

Longshore currents flow counterclockwise along the upper Texas coast, but from the mouth of the Rio Grande River they set clockwise, to the north (Lohse, 1955). At the converging place of the opposite currents, at about 20° North Latitude, the excessive water returns seaward as a countercurrent, which is locally known as ’'Whirlpool of the Gulf" (Fig. 13, inset). The general movement of sands dis­ charged by the Rio Grande and Colorado-Brazos rivers and the mater­ ials eroded from the delta fronts follow the predominant longshore currents, a fact well established through heavy-mineral analyses

(Bullard, 1942; Lohse, 1955; Curray, 1960).

That both the Texas eolian plain and the complete filling of the lagoon behind the barrier arc (Fig. 13, inset) are centered in the westernmost part of the barrier system where the two opposite Fig. 13. Interdeltaic barriers and offshore topography near Rockport, Texas. Gulf bottom contours after the U.S.C.G.S. Chart 1285. currents converge emphasizes the importance of littoral drift in barrier beach processes. Most of the excess sediment available here is carried over the island into the lagoon by storms and predominant east winds (Price and Gunter, 1943; Lohse, 1955).

The magnitude of the barrier arc is huge both in continuity and xtfidth. Barrier beaches are separated from the paralleling main­ land shore by more than 6 miles, on the average. The Rio Grande and Colorado-Brazos rivers are primarily responsible for supplying sediment directly into the Gulf throughout late Recent times,* but a large delta lobe has not been built. As mentioned previously, there is no evidence that the above two deltas are the products of filling of large inundated river mouths or estuaries such as Mobile and Galveston bays since establishment of the near stillstand.

Curray's generalized cross section of late Quaternary sediments along a line perpendicular to the coast near Rockport., Texas (Fig.

13), illustrates the continuous facies of basal sands or the

"regressive littoral sand sheet" on the continental shelf. This sheet overlies a pre-transgressive incised surface and emerges above sea level as the barriers (Curray, 1964; Fig. 14). The Gulf bottom topography here is very smooth, with parallel hydrographic contours

(Fig. 13), in contrast to that along the northwestern Gulf coast of

Florida.

The last stage of sea level rise and barrier island evolution is best illustrated in Fiskls detailed sedimentary facies diagram across Padre Island (Fig. 15). According to Fisk, Padre Island and

-Here Recent refers to the interval since sea level commenced its last major rise to the present. Sh• tf facias mudi 20 Bay facias 40 Basal facias sands 60

80 FATHO/AS 100

0 10 20 30 40 70 MILES60 Fig. 14. Recent sediments of the continental shelf in a line per1 pendicular to the coast near Rockport, Texas. See Figure 13 for location of Rockport. After Curray (1963).

Baach and dun*

0 FEET Waihoviri

S h o ro fa c *

WEstuary

Pleittocone '///////////, /y/yyO % &$$$• V M M M M z z f p Eolian plain m m 60 6 MILES

Fig. 15. Recent sediments across Padre Island, Texas. The lagoon has been filled completely. See Figure 13 (inset) for the location of cross section. After Fisk (1959). the associated lagoon "began to form slightly more than 5000 years

ago when the sea had risen to within 20 to 30 feet of its present

level.... The Gulf shore then was slightly inland but very close to

the modern shoreline." His cross section of sediment facies and C-14

dates show that Padre Island has evolved upward from mainland beaches

or incipient or existing barrier complexes since that time. The

decelerating rise of the sea around 6,000 years ago (Russell, 1967) was probably accompanied by a continuous supply of littoral sands.

If sediment supply remains sufficient and there is a decreasing rate in rise of sea level, an enlargement or accretion of a beach will result. If this occurs against a low sloping mainland, the area immediately landward of the beach will be drowned.

Assuming that the overall Texas barrier arc between the two deltas is a subaerial extension of Currayls basal sand sheet of the continental shelf, the barrier chain is not merely a product of spit growth, even though littoral drift is an important factor. Nor is it an emerged landform. The modern Texas barrier beaches are an end product of the continuously existing Gulf beaches throughout the late Recent times.

Risk reports that ancient beach deposits, exposed in the banks of some of the passes scoured through Padre Island near the place where the gulfward countercurrent occurs (Fig. 13, inset), reach elevations comparable to the modern storm berm. They'under­ lie a series of ridges and swales now largely buried by sand dunes.

The earliest formed beach ridge lies'more than a half-mile from the Gulf beach. The sequence of the beach- ridges marks the gulf- ward accretion of the island since the stillstand. At the'present time, however, p'rogradation by beach ridge accretion is not occurring. The present absence of beach ridge development along Padre

Island is associated with development of a 20- to 30-foot-high

single-crested dune ridge. A broad, flat "hurricane beach" in

front of the dune ridge averages 200 feet in width (Fig. 16). It

is covered by a "coarse shell pavement", that is formed residually

by wind deflation toward the lagoon (Hayes and Scott, 1964). Now

the excess material brought in by littoral drift, which is mostly

carried over into the lagoon, may not be sufficient to build beach,

ridges in a coast that has high-energy waves and strong winds from

the easterly quadrant most of the year (Lohse, 1955).

Today the Rio Grande and Colorado-Brazos rivers carry a very

small discharge in proportion to their large drainage basins (Table 1).

Sediment load is related to discharge.' Although the exact reason for

the low discharge is not known, agricultural irrigation to compen­

sate for the arid climate of the region and other reservoir systems

have diminished the waters markedly, as shown by the fact that,

these rivers are decreasing in volume downstream. The reduction in

.river discharge could have influenced the volume of sediment deposited

into the Gulf for transport by longshore currents. Long-term cli­

matic change can be taken into.account, because a slight increase

or decrease of precipitation over a large drainage area can signifi­

cantly affect the discharge (Barton, 1930).

Deltaic plains of the southwestern Texas coast are undergoing

regional transgression. The rivers no longer carry sufficient sedi­

ment to advance the entire delta seaward. The Pleistocene Beaumont

formation is directly exposed within the surf zone at Sargent Beach.

(Fig. 13, inset). Calcareous nodules similar to those near High. Island are present on the beach. Abandoned meandering channels are truncated along the beach front (LcBlanc and Hodgson, 1959). The

Rio Grande Delta likewise does not prograde. . Exhumed marsh deposits are exposed at the mouth of the river (Fig. 17). Rusnalc (1960) mentions Rio Grande,Delta material of Pleistocene age cropping out along the nearshore Gulf bottom.

Matagorda Peninsula, which is attached to the Colorado-Brazos

Delta at its northeastern end,- has been undergoing severe erosion.

This peninsula, a barrier spit about 50 miles long and less than a half-mile wide, has often been breached by high storm waves which leave a number of intermittent passes or inlets (Fig. 18). Usually these passes are gradually closed by downdrift sediments from the northeast in periods of normal weather, but permanent closure of the passes is seldom accomplished because they are reopened by hurricanes and storms (McCrone, 1956).

Probably the severe erosion of the peninsula may have some connection with the channel shifting of the Colorado River. Formerly, the river occupied the course of Caney Creelc and deposited its sedi­ ment load near Sargent Beach directly into the Gulf, as the Brazos

River does (Wadsworth, 1966). According to Wadsworth, with the shifting of its course to the present position, which occurred about

60 miles inland from the Gulf shore, the Colorado River flowed into

Matagorda Bay. This resulted in the sediment being trapped in the bay, with little reaching the Gulf. Even though the small and narrow estuary occupied by the river filled rapidly, the-formation of a new delta in Matagorda Bay was retarded by an upstream log raft. The raft obstruction occurred 12 or 15 miles above Matagorda Fig. 16. Broad beach flat and dune ridge of Padre Island, about 15 miles north of the Rio Grande River.

rtjZjL'-J&T*'!- > ki -v V n

Fig. 17. Exhumed marsh deposits at the mouth of the Rio Grande River. The Gulf of Mexico can be seen in the upper right. Bay in 1837, and by 1925 had clogged 46 miles of the river course.

Flood waters impinging on the raft inundated the lower Colorado

River area almost annually. Removal of the raft in 1925 and 1929

initiated the construction of the delta in Matagorda Bay. By 1936

a narrow delta had formed across the bay and began discharging

directly into the Gulf.

Present knowledge is not sufficient to provide understanding

of the entire story of the changing contribution of sediment to the

Gulf by the Colorado River, but Wadsworth’s study provides back­

ground. He pointed out that for an uncertain period of time the

river did not supply materials through the Colorado-Brazos Delta

to Matagorda Peninsula. Since the development of the peninsula

results largely from sediments contributed by both rivers, the point merits consideration.

While Matagorda Peninsula has been undergoing destruction,

Matagorda Island apparently has prograded. Figure 19 displays a well- preserved beach ridge system on the seaward side of the island. The

island is twice as wide as the peninsula. Consequently, the two

ends are offset from one another by the inlet of Pass Cavallo, the

only large tidal inlet along the southwestern Texas coast. The

offset likely res.ults from beach ridge construction, with the sedi­ ment discharging from Matagorda Bay through the pass. Lohse ( 1 9 . 5 5 ) .

describes the effect of the famous "norther" *n.nds of the winter:

Pass Cavallo, draining Matagorda Bay, is the only major pass on the Texas coast still in a natural state of equi­ librium. The pass is maintained by the action of some 15 to 20 northers which reach the central Gulf region yearly. These.are winds- of at least 20-knot velocity, of which, one to six are from November to March and last from 1.; so as much as 3.5 days. During this time- they drive tiv* .iters _ Fig. 18. Deteriorating Matagorda Peninsula, about A miles southwest of the new Colorado River mouth. Matagorda Bay is at the top of the photo. Vertical air photograph taken by the U. S. Navy in 1961.

Fig. 19. Pass Cavallo. Matagorda Island on the left is twice as wide as Matagorda Peninsula on the right. Notice turbulent currents discharging from the bay and the beach ridges on the island. Vertical air photograph taken by the U. S. Navy in 1961. of these shallow bays southward with such violence that an outlet is maintained as near due south of the main body of bay water as possible.... Thus, the material from the bay is distributed down the coast, building Matagorda Island.

Price (1947) indicates that the northers make the tidal inlet run lik

a river in flood.

Storms and hurricanes, which strike the Texas coast frequently in the summer and fall, raise the bay water as much as 15 feet above mean low tide (U.S. Army Corps of Engineers, 1957). Waters draining seaward following passage of the storm result in erosion and trans­ portation of bay sediment to the Gulf as effectively as the flushing action generated by the northers.

MISSISSIPPI DELTA BARRIER ISLANDS

Barrier beaches are characteristic of both the active bird-foot delta and the abandoned subdeltas of the Mississippi River.The morphological details of barriers in relation to their associated subdeltas are largely determined by sediment influx from the active river, erosion of abandoned delta fronts,, subsidence, and wave action

Bird-foot Delta Submarine Bars and Barriers / Near the Head of Passes (Fig. 20), the modern Mississippi River branches into major distributaries, which flow into the Gulf. Each pass progrades seaward by extension of both subaerial and subaqueous natural levees and associated distributary mouth bars. Between principal passes are triangular-shaped, shallow interdistributary bays and associated marsh surfaces laced with tidal and distributary crevasse channels.

Russell (1948, 1959) reports submarine bars and beaches which are submerged at high tide and which, are nearly continuous around the periphery o f •the bird-foot delta (Fig. 20). On air photos such f t 8 9 °i s ' 89° W.

VENICE 29°1S'N.-

29° N.-

89. 30' W . 89 15 89? W .

Fig. 20 Submarine bars(stipled area in map) around the bird-foot delta of the Mississippi River. After Russell(1943). bars are distinguished by breaking waves, but they are usually not

shown on charts. According to Russell, the deposits are composed

of fine sand, silt, and shell, and the shallow bars extend tangcntially

to the distal ends of passes. The bars are so shallow that one may wade for long stretches during low water conditions.

A sand spit more than 1 mile long (Fig* 21) has developed down-

drift from South Pass; it is a subaerial portion of the shoal arc shown in Figure 20. Russell indicates that waves and littoral cur­ rents formed such deposits from the coarsest material available for transport at the distributary mouths.

Barrier Islands Fronting the Lafourche Delta

Prominent barrier islands such as Timbalier islands, Isles

Dernieres, and Grand Isle are encountered around the most recently abandoned Lafourche Delta (Fig. 22). Before the Mississippi River diverted to its present course about 1,000 years ago, it flowed to the Gulf through the Bayou Lafourche area, which the Mississippi

River began to occupy about 1,800 years ago (Peyronnin, 1962).

Bayou Lafourche maintained a small discharge until 1904, when its head at the modern Mississippi River, about 80 miles upstream from the Gulf shore, was dammed. As the Mississippi River shifted to its present course, the growth of the Lafourche Delta ceased, and with continued decrease in discharge its gulfward margin experienced erosion by w ave attack. According to Fisk (1955), development of a series of beach ridges adjacent to the distal end of Bayou Lafourche distributaries was contemporaneous with the final stages of seaward lengthening of the Lafourche-Mississippi system.

Peyronnin shows that the mouth of Bayou Lafourche receded Fig. 21. Sand spit at the mouth of South Pass. Oblique air photograph taken by the author in 1968. vw.«* 'I E i m m Co.ioVij;. »■?

Timbalier Bay L-• IV f7.il*'. wi„: ,.c°i,,ou ■ 1 8 4 5 uio oo*n'*r* I 0 M U E 8 °/ior I.

Catto Toto I. ^

Wine I,

Otrni**® Caillou I, 1 8 8 7 lOMues

u%* I flVL vT *••5

Terrebonnea Bay ^ Brush l.t MX 1

■» B. Timbalier l*fei Dern'0’** '• I. ‘ iomubs

Fig. 22. Barrier islands and shoreline changes in the abandoned subdeltas of the Lafourche-Mississippi River. approximately 6,650 feet between 1890 and 1959 (Fig. 23), and that

the rate of recession was greatest in the years following its

closure in 1904. Similarly, the Timbalier islands to the west have experienced considerable recession and have extended down-

drift through erosion on their eastern and accretion on their western ends. Additional sediments are derived from erosion of delta-front material. Grand Isle has experienced similar reces­ sion and downdrift extension (Myers and Theis, 1956) but to a lesser degree because this section of the coast lies along a more protected area of the Gulf than the Timbalier islands. Deltaic desti'uction has likely provided the main source of materials for development of Grand Isle and the Timbalier island complex. The mode of island development has primarily been through spit growth, with eventual deterioration of the leeward marshlands into open waterbodies.

The Lafourche area is a complex of several older deltas and subdeltas. On the western side the older deltaic surface has been buried by Lafourche-Mississippi deposits. The Lafourche-Mississipp initially flowed through channels associated with Bayou Petit

Caillou and Terrebonne (Fig. 22); later, Bayou Lafourche became, dominant. The map of 1845 (Fig. 22) shows the delta position and other Lafourche-Mississippi distributaries to the west. These dis­ tributaries formerly extended farther seaward than the present islands; through subsidence and shoreline regression the beaches remain as islands. Islands such as Caillou, Wind, and Isles

Dernieras are likely related to the Lafourche-Mississippi distribu­ taries west of Bayou Lafourche. An inner island complex landward '— .890 GULF OF MEXICO (a) Islet Dtrmeret

0 1 2 3 4 Bayou 1 I I I I Lafourcht Scale in miles

I-,.'.£-A

sf N*\- -- G t/£ f O f MEXICO Kao-'*^ri-=tSrL

Fig. 23. Shoreline changes of Isles Dernieres and Timbalier islands in two different stages of develop­ ment.- After Peyronnin (1962). of tlio Timbalicrs, consisting of Brush, Casse i'ete, etc., have likely formed as spits from Lafourche-Mississippi relict channels which flowed into Timbalier Bay.

The sediment facias diagram of Isles Dernieres (Fig. 24) shows barrier sands overlapping extensive marsh deposits along the seaward side of the islands. Such a sequence occurs along the entire length of the barrier (Peyronnin, 1962). This facies is the result of regres­ sion of the islands across the abandoned delta front. Until 1837,

Isle Derniere was a single island, as its name implies, but it has since been eroded and breached. These islands are now identified as

Isles Dernieres. The recession and disintegration of the islands are probably due to the loss of sediment source from the east and continued subsidence. The lagoon behind the barriers is expanding.

Barrier Islands Fronting the St. Bernard Delta

Similar to the Lafourche-Mississippi barriers, the Chandeleurs and associated islands lie seaward about 25 miles from the marshy mainland of the St. Bernard Delta. This delta was active approxi­ mately 2,800 to 1,600 years before present (Kolb and Van Lopik, 1966).

The Chandeleur Islands, Breton Island, and a line of arcuate shoals form the barrier arc, convex to the Gulf (Fig. 25). The islands are principally comprised of sand and shell, Distributaries of the St.

Bernard Delta radiate in a palmlike pattern from an apex about 30 miles east of New Orleans; they originally extended seaward of the present Chandeleur arc. The original delta surface now lies about

15 feet below sea level in the central part of the Chandeleur islands (Russell, 1936).

Most of the shells in the outer beaches are Ostrea, Rangia, and other brackish or fresh-brackish water fauna. Waters surrounding TIMBALIER ISLAND 0 FEET iii—pi ", ...* >>*• ... 11 i i i i 1 I1, •«»#i 1

20 Boy bottom 40 2.0 MILES ISLES DERNIERES 0 FEET D vi'JV i " • v" ir^in>y- *‘ *•>•*. Y*I £ {L*;*7 "'Delta complex 20

#N ______40 1.0 MILES CHANDELEUR ISLANDS 0 FEET

20

40 1.0 MILES

Fig. 24. Sediment facies of delta barrier islands. Barrier sands are undifferentiated. The diagrams of Timbalier Island and Isles Dernieres are modified after Peyronnin (1962) and that of Chande­ leur islands, after Treadwell (1955). 48

IAHC POHrCNARTBAtN.

LAXC OORQNC

•It*jo N

W.

Fig. 25. St. Bernard Delta and the Chandeleur arc. After Russell (1948). the islands are far too saline for the growth of Rangia today

(Russell, 1936). Pottery from Indian sites which were likely

located on natural levees of St. Bernard-Mississippi distributaries

is found along the beach. Under wave attack the entire Chandeleur

arc is moving westward at a rate of one-quarter mile per century

(Ludwick, 1963). As the beach, is driven toward the land, a fringing mangrove swamp along the lee side of the islands is being buried by beach- sands, and decayed mangrove stumps are exhumed along the Gulf side (Russell, 1936; Morgan and Treadwell, 1954).

Fisk (1955) believed that the delta-front islands, which might have developed as bay-mouth barriers around the original periphery of the St. Bernard Delta, were destroyed by wave attack, and that the present arcuate groups formed at the seaward margin of the sub­ sided delta plain. However, it is likely that the Chandeleurs have existed without disappearance, but have experienced modification.

The magnitude of Chandeleur Sound reflects the degree of subsidence and deterioration of the former St. Bernard-Mississippi deltaic plain.

Facies diagrams of sediments (Fig. 24) are suggestive of the developmental systems. The youngest barriers, such as Timbalier and

Grand islands, are composed primarily of barrier sands and are separated from the mainland marshes by open waterbodies. These islands are undergoing both lateral extension and regression. This indicates a relatively rapid deterioration of the most recent deltaic mass. • Figure 24 indicates that barrier sands are regressing over bay bottom deposits.

Isles Dernieres are thought to be an older sequence than the

Timbaliers and consequently are regressing less rapidly and are nearly stable laterally. These islands are regressing against firmer and relatively older marsh deposits, as is shown in Figure 24.

The Chandeleur Islands are the oldest of the deltaic barrier island systems and are regressing less rapidly than the others.

Retarded rates of regression with age appear to be related to rela­ tive amounts of compaction and subsidence since formation. If the

Chandeleur arc is a modified form of earlier barriers, and the earlier barriers had developed as other delta barrier islands have, it can be stated that the island arc was initiated by wave attack and littoral drift.

Although the St. Bernard Delta underwent a considerable sub­ sidence, the Chandeleurs could be maintained because of several reasons. First, the islands are being pushed back across their own mangrove swamps, which seem to be composed mostly of sands (Russell,

1936). Second, the depressed deltaic surface is attacked by waves, particularly during storms, and the eroded materials are added to the beach. The shells and pottery from Indian middens and unindu­ rated slabs of delta silt along the beaches are evidence of this.

A borehole on the inner side of the beach at approximately the easternmost point of the Chandeleurs yielded undisturbed delta deposits at 15.5 feet below sea level (Russell, 1936). As was observed with the calcareous nodule beach near High Island, Texas, sediments are supplied to the beach from the shore zone where erosion is occurring. Third, the Chandeleurs could subsist, because "the arc is growing smaller as it advances toward the coast and less material is needed to maintain It" (Russell, 1936).

Shepard (I960) believed that the upgrowth of a barrier island is > probably due to an offshore sediment supply "in. view of the definite evidence of sinking of the Chandeleur Islands," but the effect of the island’s migration inland seems to be too great to give any evidence of such ail upgrowth.

BARRIERS OF THE WEST COAST OF THE FLORIDA PENINSULA

AND THE APALACHICOLA AREA

The Apalachicola and the lower Florida coast barriers are de­ scribed here together merely because little is known about their depositional history in comparison with that of the other Gulf coast barrier islands.

Barrier Islands of the West Coast of the Florida Peninsula

The west coast of the Florida peninsula is flanked by fairly continuous, narrow barriers, with some intervening mainland beaches.

The barriers extend more than 130 miles from Anclote Keys to Sanibel

Island (Fig. 26, inset). All the barriers are low and flat and have no conspicuous dunes (Martens, 1931). They are generally close to j the mainland shore and are probably shallowly based at a depth less than 15 feet, beyond which is the gently sloping, irregular Gulf bottom topography of the continental shelf (Fig. 26). Tidal inlets are numerous and wide, even though tidal ranges and lagoons enclosed by barriers are small.

The drainage area and discharge of the rivers flowing into estuaries are small, and a minimum of detrital sediments has been supplied to the coast from the flat Icarst topography of the Florida peninsula (Price, 1954a). The headlands that might have contributed barrier sands are also small. Barrier beaches have much, shell material incorporated in quartz sand (U.S. Army Corps of Engineers, 52 4

V I ANCLOTE 3 MILES i + CONTOURS IN FEET

-4-HONEYMOON ISLAND A, J -I- + + + + + + + ■*• + + + + + + + + + + + + + + CALADESI ISLAND ft /+ + + + + + +- + + + + Tampa Li + + (Mioc.n.) + + + + + + + + + -4-ClEARWATER REACH ISLAND + + + + + + + + + + + + + + + + + AV /r + + ■«• + + •f + + + + + + + + + h /+ + + •*• + + + + + + -f + + + + + + + + + + + + + + + + + + + + •*• -^SAND KEY+ + s s s s + w m m m , INDIAN ROCK Calooiohatch** Marl ■► + + + +

MAP AREA TREASURE ISLAND SaMbal I.

Fig. 2 6 . Gulf bottom topography of the Florida west coast and adjacent mainland geology. Shorelines of the last inter- glacial period(Pamlico terrace) are indicated in the inset map by hachure marks(after Cooke, 1939). Offshore contours and mainland geology after the U.S.C.G.S. Chart 1257 and Cooke(1945) respectively. 1954). Sandy limestone along the mainland coast and coastal beaches of the previous interglacial period may be the source of the quartz sand.

The barrier islands are undergoing beach erosion. In many places the coastal sands have..been winnowed, leaving spotty coquina or beach rock outcrops exposed to protect the beaches (Martens,

1931; Gould and Stewart, 1955; Bruun, 1959; Tanner, 1960c). Accord­ ing to Gould and Stewart (1955) , outcrops of beach roclt consisting of Pleistocene and Recent shell fragments and sands firmly cemented with calcium carbonate occur slightly offshore, from low tide to a depth of about 12 feet. The longshore currents are variable, though, the southward drift is stronger than the northward (Cooke, 1945;

Price, 1954a; Bruun et al., 1959).

For the sake of convenience the area covered by Figure 26 has been chosen for the explanation of some aspects of the little under­ stood barriers of the west coast of the Florida peninsula. According to Cooke (1945), Tampa Limestone of Miocene age, which is a fairly hard, commonly chalky, sandy limestone, underlies most of- the mainland coast back of the barrier islands. He reports that about 3 feet of hard, white, sandy limestone is exposed on the Gulf shore at Indian

Rocks, the westernmost promontory of the west coast, which is over- lain by 2 or 3 feet of coastal sand (Pamlico sand)* of the previous

interglacial period.

^According to Cooke (1945), the Pamlico sand in most parts of Florida is composed chiefly of quartz grains. Toward the south the sand is a foot or two thick, but it becomes thicker farther north. It does not much exceed 20 feet in thickness in peninsular Florida. The Pamlico terrace (Fig. 26, inset), which forms- the surface of the Two opposite predominant drift sets influence the area around

Indian Rocks: a northward drift about 22 miles to Anclote Keys, beyond which the scro-energy coast occurs, and a southward drift

toward the mouth of Tampa Bay (Price, 1954a). As sea level approached stillstand, the shallow shoals off Indian Rocks presumably constituted a major source area, supplying the barrier-forming sediments to the north and south by means of the prevailing longshore drift. The irregular topography beyond the depth, of 18 feet off the barrier islands (Fig. 26) indicates that beach development was not signifi­ cant during the sea transgression. Most of the continental shelf off the barriers is hard rock, chiefly limestone, and a thin veneer of detrital sediments is present in local areas and fills some of the shelf depression (Lynch, 1954; Price, 1954a, 1954b). If there had been abundant sands available for the beach development, the irregu­ lar topography should have been buried. No linear sand bodies are detected in the nearshore Gulf bottom on the chart. It is uncertain whether the barriers regressed toward the' mainland coast or main­ tained an upgrowth with the rising of sea level to its present posi­ tion, or whether they have developed as spits since the establishment of near stillstand.

The barrier beaches are undergoing extensive erosion (U.S. Army

Corps of Engineers, 1954; Bruun, 1959). Anclote Keys, the northern­ most island, is separated from Honeymoon Island by some 6 miles of open water. The shoal 1 to 2 feet deep between the above-mentioned

Pamlico sand but includes also large areas not reached by the sand, fringes the present shore nearly everywhere and extends up former estuaries. two islands (Fig. 26) appears to be an eroded relict feature of a

former island. The problem from drift interruption by inlets is not

severe along the coast (Troxler, 1959), probably owing to the small

amount of sand in transit. Generally these barriers are not growing

but are decaying (Zenkovich, 1967). The sediment source area did not

'contribute much material originally and formed only small and narrow

barrier islands. The Tertiary limestone may be fairly resistant in

a medium wave-energy coast, and it is also conceivable that the amount

of sediment from the source has been' decreasing since the establish­

ment of the stillstand.

Apalachicola Barriers

There are four barriers in the Apalachicola area: from the

east, Dog, St. George, St. Vincent islands, and St. Joseph Spit (Fig.

27). The barrier coast is subjected to low to medium wave energy,

as defined by Price (1954b). The coastal energy decreases eastward,

eventually to sero east of the barrier system.' Longshore currents,

and drift are to the west at present (Tanner, 1964; Gorsline, 1966).

The Apalachicola River, the' second largest river of the north­

eastern Gulf coast after the Mobile River complex, flows into

Apalachicola Bay. The river has built a delta approximately 8 miles

wide in its estuary, but characteristic features of a Pleistocene-

Apalachicola delta exist from Panama City eastward beyond the barrier

islands, a distance of about 100 miles, and inland for about 50.

miles (ICofoed and Gorsline, 1963; Tanner, 1966). Generally speaking,

the Apalachicola barriers have developed on the flanks of the Pleisto­

cene delta.

Two digitate shoals normal to the coastline extend southward i {‘M «■ J tl v£,-ST JOSEPH V?‘/m •*, ‘ " '

4 w t rwrS V

HWco G d FUJI //0*c .7 sj •I w*S 5J /><*«

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1114 2?* Ap^ chicqla barr±ets offshore topography. Depth in fathoms. From the U.S.C.G.S. Chart 57

from capes San Bias and St. George (Fig. 27 A and B) for approxi­ mately 10 miles. Shepard (1960) mentions that pre-existing shoals of coral growth on the shelf favor deposition between gyrols and hence the building out of the cuspate points.

In contrast, Tanner (1960b, 1961) believes that both the barriers and shoals have been formed by an excessive supply of sand from the Apalachicola River since the stillstand in view of the low wave-energy level. The coastal energy is explained as being too low to handle the sand supply from the river. Hsurs petrological study (1960), however, shows that most of the barrier sands are similar to the sand of the Pleistocene delta in grain size and mineralogy rather than to the river sediments. Hsu thought that the beach sands were derived by reworking of Pleistocene material and that the modern Apalachicola River has not contributed much sediment to the barrier beaches.

ZERO-ENERGY COAST OF FLORIDA

The northeastern Gulf coast of Florida between the Apalachicola barriers and Anclote Keys, a belt some 150 miles long, is not bor­ dered by elongate barrier islands or mainland beaches (Fig. 1), The. shores are marked largely by swamps or marshes. In’the Gulf bottom are many trenches that appear to be drainage channels which were incised before sea transgression (Cooke, 1945; Fig. 28). Price Cl954b) mapped the inner continental shelf of this coast as "unfilled stream valleys."

The mainland shore here deepens gradually toward the inner continental shelf, with a regional slope of 1 or 2 feet per mile. This contrasts with the steep shoreface of 50 to 60 feet per mile along the section of Santa Rosa Island and the Red Bluff. \ MAP AREA

AnclofK«yiJ •

^ 0 1 ? 3 MltES 1---1-- 1--I CONTOURS IN FEET

°c°ocAt

28* Cff®h°^e toPography in the zero-energy coast of Florida. Gulf bottom contours after the U'.S o.b.b. t/hart 1259. This coast is lacking .in wave action. Price (1954a) classified it as a zero-energy coast (Fig. 2). Keulegan and Krumbein (1949) made a theoretical study of the critical steepest slope of a conti­ nental shelf across which waves from deep oceanic waters undergo a gradual deformation and energy loss. By the time they arrive near shore, waves axe too weak to break or develop shore structures such as beaches or bluffs. Comparison of the theoretical curve with the actual profile from the zero-energy coast of Florida shows that the two curves closely correlate and are identical in overall gradient

(Fig. 29).

The classical concept that a barrier island must form on a gently sloping sea bottom for a coast to obtain an equilibrium profile is not realistic, whether it is associated with change of levels or not.

Considering the offshore slope alone as the critical factor for the initiation of barrier islands, this zero-energy coast seems to have an ideal condition. Such a concept (Zenkovich, 1967) postulates that with material and waves of given size there will-be only one ultimate profile of equilibrium toward which a shoreline evolves. A larger angle of initial sea bottom will lead to coastal erosion, and a smaller angle to accretion. If the angle of the original surface of the bottom is so small that wave energy begins to fail before the water's edge is reached, a profile of equilibrium will be pro­ duced by the formation of a barrier beach which shifts the former shoreline seaward, leaving a lagoon between the old shoreline and the new. In the northern Gulf coast, however, wave condition is largely dependent on the offshore profile (Fig. 29), and it follows that coasts with different offshore slopes can not possess equal energy waves. THEORETICAL CURVE

4 0

6 0

-J 8 0 0 2 4 6 8 30 12 MIL

Fig. 29. Comparative Gulf bottom profiles. Steepness of bottom correlates with increasing wave energy. The theoretical breaker- less profile is compared with a beachless sector of the north­ eastern Florida coast. (1) Net Spread Key, Florida (28°38', 82°40'); (2) barrier island 10 miles north of Cape Romano, Florida (26°03r, 81048'); (3) Padre Island near Corpus Christi, Texas (27°35', 97°13'). After Price (1954a). SEDIMENTARY FACIES OF BARRIER ISLANDS

Detailed sedimentological study of the barrier island structure is one of the best methods to reveal its past history, but insufficient studies have been made compared to the large amount of available obser­ vational data. Along the Texas coast, where the pattern of littoral drift has been well studied, sediments toward barrier beaches are well-sorted coarse materials, but toward offshore they become poorly sorted mixtures of fine sands, silts, and clays which are usually churned by bioturbation in water deeper than 30 to 40 feet (Hayes and

Scott, 1964; Bernard and LeBlanc, 1965; Shepard and Moore, 1955).

The most detailed sedimentological studies, as In Grand Isle and

Padre Island by Fisk (1955, 1959) and Galveston Island by Bernard and LeBlanc (1965), show that sediments become fine grained verti­ cally downward as well as offshore from the beach. This depositional sequence is highly suggestive of the mode of barrier island formation.

Grand Isle. The framework of this island consists of a series of low arcuate beach ridges, each, of which curves bayward away from the beach (Fig. 30). The beach ridges' are unified on the seaward side by the active beach and sand dunes. The arrangement of beach ridges and their relationship to the Lafourche' Delta plainly sug­ gest that Grand Isle originated as. a bay-mouth spit (FisK, 1955).

Figure 30 shows the sedimentary facies that comprise the island and underlie the adjacent Gulf bottom as. interpreted by Fisk (1955).

Fisk recognized three major facies: (1) well-sorted homogeneous sands, including the subaerial beach and dune sands, and subaqueous inner shoreface sands, (2) less well sorted outer shoreface sands and silty clays, and (3) thin Gulf bottom muds which are materials Barrier sands MILES Shoreface sands and silty clays

Gulf bottom mud

Beach ridge

Gulf bottom contour in

kill* - .W«| u_ ”

-‘•••'.v.v \« < ♦« « i .« ».

iSBESSsSSSSS&S?

GULF O T M E X W O A 24

/ w

FEET 20

^Prodelta silty clays 40 Marsh Kvv> GRAND ISLE silty clays 60

0 0.5 1 1.5 MILES GULF OF MEXICO

Fig. 30. Sediment facies of Grand Isle. After Fisk (1955).

cr> reworked by wave action from the older prodelta clays that were laid down beyond the Lafourche Delta. Few sands are recorded from a water depth of more than 20 feet. In cross section, massive clean sands comprise the upper part of'the island and grade downward into alter- nating sands and silty clays resting upon older clay deposits. Thick­ ness of sandy deposits increases locally to a depth of more than 50 feet through compaction and subsidence of the Gulf bottom under the sediment load.

This depositional facies, both vertical and offshore, is devel­ oping as the sediments brought by longshore drift are deposited in the bay at the downcurrent end of the island. Sands settle first near the beach, but finer grained materials travel farther into deeper water.

Galveston Island. The same sedimentary sequence is. encountered in Galveston Island, the structure of which, has been studied by LeBlanc and Hodgson (1959) and Bernard and LeBlanc (1965). Well-preserved, numerous beach ridges almost parallel to the present shoreline characterise the progradation of this island by continued addition of sands by littoral drift (Bernard and LeBlanc, 1965; Fig. 31).

Figure 31 shows well-sorted barrier sands nearshore grading downward into interbedded sands and silty clays. The vertical sequence of sedimentary features downward from the island surface corresponds closely with the offshore suites from the beach to the inner conti­ nental shelf.

Through beach ridge patterns, geological and sedimentary struc­ ture of the shallow subsurface, and C-14 dates, it can be inferred that the steep Pleistocene surface beneath the island behaved as a Barrier sands

Shoreface sands and silty clays MILES Beach ridge M Golf bottom contour in feet

WEST BA Y

TyrtAfieh*— fliikAAftiMHi— rt—iTilr^riir«arii»iriir*n *ti‘»■>»OTi'wirn^ti *«*■ *i11~ Time linos in years.B.P. a' 0 FEET GALVESTON ISLAND:::::

Bay deposits Pleistocene

6 MILES GULF OF MEXICO

Fig. 31. Sediment facies of Galveston Island. After Bernard and LeBlanc (19.65)

.c-ON wall against the Gulf. The barrier beach of Galveston Island developed

rapidly along a considerable stretch of the coast after sea level

reached its present position, and the island prograded with accretion

of parallel beach ridges along the shore. This is quite in contrast

to Grand Isle, which extended as a growing spit across a bay bottom

with recurved beach ridges.

There arc two contradicting opinions with regard to the direction

of the predominant longshore drift at Galveston Island. Because

( Galveston Island is "wide and blunt on the northeastern end and tapers

to a point to the southwest" like Matagorda Island, Bullard (1942)

believed that the materials brought out of Galveston Bay might have

been transported southwestward, building up the island. Later

writers expressed the same opinion. Undoubtedly, the' bay contributes

sediment. The mean range of diurnal tides is less than 2 feet, but

the strong "northers" of the winter have been known to depress the

water surface as much as 4.3 feet below mean low tide, causing the

flushing action, as in Matagorda Island, and tropical hurricanes

have raised the bay water as much as 15 feet above sea level (U.S.

Army Corps of Engineers, 1958).

Prior to the construction of the' jetty at the northern end of

Galveston Island (Fig. 31) between 1887 and 1897, recession of the

shoreline had been marked toward the'northern part of the island,

but since jetty construction a decided accretion has been taking

place behind the jetty and has resulted in beach advance of over

a mile. Beyond the accreting stretch, the Galveston beach front

began to undergo gradual erosion. The rest of the island does not

show any indication of significant recession. The material eroded 66 from the city front has been arrested and deposited in the pocket framed by the jetty. A number of observations of littoral currents along the beach over a short period of time by the U.S. Army Engineers .

(1953) showed movement in both directions, but originally the jetty was constructed to cut off the sediment moving northward into

Galveston inlet (Russell, oral communication). Johnson (1956) esti­ mated 437,599 cubic yards of sand drifting northward annually.

Galveston Bay contributes barrier-forming sediment, but it is tentatively assumed that the predominant littoral drift comes from the direction of the Colorado-Brazos Delta.

SUMMARY AND CONCLUSIONS

Johnson*s hypothesis of barrier island formation was based on offshore profiles. His assumption that the original profile before the initiation of barrier island development descended from shore to the continental shelf with the same slope as characterises the adjacent land surface is not always realistic in the northern Gulf coast (Fig. 32).

3arrier islands along the northern Gulf coast evolved during the post-glacial sea level rise, but the mode of development In every barrier island is directly related to such factors as sediment sources, drift patterns, coastal configuration, and offshore slope.

No simple generalization on their formation can be made.

Santa Rosa Island and Mississippi Sound and Bolivar Peninsula barriers developed downdrift of sediment-supplying coasts of Quater­ nary age. Apalachicola barriers formed on the flanks of the Pleis­ tocene deltaic plain.

The Texas barrier arc between the deltas of the Rio Grande and /Johnson’s Theory

SANTA ROSA ISLAND

Pjoisto con e Surface

SHIP ISLAND

• •

PADRE ISLAND

Fig. 32. Schematic diagrams of barrier islands. 68

die Colorado-Brazos rivers evolved upward with sea level rise either from mainland beaches or from incipient or existing barrier complexes.

These major rivers must have contributed the bulk of barrier island sediments through the converging drift sets between the deltas.

Major barrier islands around the Mississippi ‘Delta have devel­ oped as bay-niouth barriers on the flanks and against abandoned natural levees and distributary mouth bars of the subdeltas. The Chandeleur arc represents an advanced stage of bay-mouth barrier development around an older delta lobe.

Besides the upcurrent coastal sources of Pleistocene .material and the rivers, large estuaries such as Mobile and Matagorda bays also supply sediment to the barrier beaches. In all cases, littoral drift is the primary factor in transporting barrier-forming sanda from the source and in initiating or sustaining barrier island development along the northern Gulf coast. No genetic distinction can be made between the spit and barrier island growth.

Coasts such as the stretch, between Destin and Panama City,

Florida, and the zero-energy coast of Florida do not have barrier islands. In these cases the modern shoreline Is abutted against

Pleistocene deposits which supply the local source of sediments.

Sedimentological and morphological examinations of the off­ shore bottom were made. Sedimentary facies diagrams of Grande Isle and Padre and Galveston islands are suggestive of their depositional history. Bibliography

Avcs, C., 1958, A beach outcrop of marine Pleistocene Beaumont Clay, in Sedimentology of South Texas (Field Trip Guidebook), Gulf Coast Assoc. Geol. Soc. , pp. 73-85.

Barton, D. C., 1930, Deltaic coastal plain of southeastern Texas, Amer. Assoc. Petrol. Geol., Bull. 14:359-382.

Bates, C. C. , 1953, Rational theory of delta formation, Amer. Assoc. Petrol. Geol., Bull. 37:2119-2162.

Beach Erosion Board, 1950, Test of nourishment of the shore by offshore deposition of sand, Long Branch, New Jersey, Tech. Memo. No. 17.

Bernard, H. A., Major, C. F., and Parrott, B. S., 1958, The Galveston barrier island and environments: a model for predicting reservoir occurrence and trend, Gulf Coast Assoc. Geol. Soc., Trans. 9:221-224.

______, LeBlanc, R. J., and Major, C. F., 1962, Recent and Pleistocene geology of southeast Texas, in Geology of the Gulf Coast and Central Texas and Guidebook of Excursions (Ed., Rainwater, E. H., and'Zingula, R. P.), Houston Geological Society, up. 175-224.

______and LeBlanc, R. J. , 1965, Resume of Quaternary geology of the northwestern Gulf of Mexico province,' in Quaternary Geology of North America (Ed., Wright, H. E., and Frey, D. G.), Princeton Univ. Press, pp. 137-186.

Bird, E. C. F., 1961, The coastal barriers of East Gippsland, Australia, Geog. J., 127:460-468.

______, 1965, The evolution of sandy barrier formations on the East Gippsland coast, Roy. Soc. Victoria, Proc. 79:75-88.

Blanton, S. L., 1951, Origin of offshore bars, Geol. Soc. Amer., Bull. 62:14-24.

Brown, E. I., 1928, Inlets on sandy coasts, Amer. Soc. Civ. Eng., Proc. 54:505-553.

Brown, G. F., et al., 1944, Geology and groundwater resources, of the coastal area in Mississippi, Miss. Geol. Surv., Bull. 60.

Bruun, P., 1955, Stability of beaches, Shore and Beach, 23:21-26.

_____ , 1959, Present status of beach erosion and protection in Florida, Shore and Beach, 27:24-26. 70

Bruun, P. j 1962j Sea level rise as a cause of shore erosion, J. Water­ ways and Harbors Div. , Amer. Soc. Civ. Eng. , Proc. 88:117-130.

_____ 5 Asce, P., and Gerritson, P., 1959, Natural by-passing of sand at coastal inlets, J. Waterways and Harbors Div., Amer. Soc. Civ. Eng., Proc. 85:75-107.

Bullard, P. M., 1942, Source of beach and river sands on Gulf coast of Texas, Geol. Soc. Amer., Bull. 53:1021-1043.

Charlston, C. W. , 1950, Pleistocene history of coastal Alabama, Geol. Soc. Amer., Bull. 61:1119-1129.

Coe, J. J., 1966, Searching for California’s inland sand sources, Shore and Beach, 34:13-17.

Coleman, J. M. , and Smith, W. G., 1964, Late Recent rise of sea level, Geol. Soc. Amer., Bull. 75:833-S40.

Colony, R. J., 1932, Sources of the sands on the south shore of Long Island and the coast of New Jersey, J. Sed. Petrol., 2:150-159.

Coolc, T. D., 1958, Rio Grande Delta, in Sedimentology of South Texas (Field Trip Guidebook), Gulf Coast Assoc. Geol. Soc., pp. 52-53.

Cooke, C. W., 1931, Seven coastal terraces in the southeastern states, J. Washington A.cad. Sci., 21:503-513.

______1939, Scenery of Florida: interpreted by a geologist, Fla. Geol. Surv., Bull. 17.

______1945, Geology of Florida, Geol. Surv., Bull. 29.

______1968i Barrier island formation: discussion, Geol. Soc. Amer. Bull. 79:945-946.

Corbeille, R. C., 1962, New Orleans barrier-island, Gulf Coast Assoc. Geol. Soc., Trans. 12:223-230.

Curray, J. R. , 1960, Sediments and history of Holocene transgression, continental shelf, northwest Gulf of Mexico, in Recent Sediments, Northwest Gulf of Mexico (Ed., Shepard, F. P., et al.), Amer. Assoc. Petrol. G.eol., Tulsa, Oklahoma, pp. 221-266.

______, 1964, Transgressions and regressions, In Papers In Marine Geology (Ed., Miller, R. L.), Macmillan Co., New York, pp. 175-203.

_ and Moore, D. G., 1963, Facies delineation by acoustic-reflection: northern Gulf of Mexico, Sedimentology, 2:130-148. Cun'ay, J. R. , and Mooro, D. C. , 1964, Holocenc regressive littoral aand, Costa do Nayrait, Mexico, in Deltaic and Shallow Marina Deposits (Ed., van Straatcn), Elsevier, pp. 76-81.

Davis, W. M. , 1896, The outline of Cape Cod, Amer. Acad. Arts and Sciences, Proc. 31:303-332.

Do Beaumont, E., 1845, Lecons de Geologic Pratique, Paris.

Dietz, R. S., 1963, Wave-base, marine profile of equilibrium, and wave-built terraces: a critical appraisal, Geol. Soc. Amer., Bull. 74:971-990.

Doering, J. A., 1956, Review of Quaternary surface formations of Gulf coast region, Amer. Assoc. Petrol. Geol., Bull. 40:1816-1862.

Duessen, A., 1924, Geology of the coastal plain of Texas west of 3razos River, USGS Prof. Paper 126.

Evans, 0. F., 1943, The origin of spits, bars, and related structures, J. Geol., 20:846-865.

Faris, 0. A., 1933, The silt load of Texas streams, U. S. Dept. Agri., Tech. Bull. 382.

Fisk, H. N., 1955, Sand facies of Recent Mississippi Delta deposits, 4th World Petrol. Congr. Proc., Sec. 1-c, pp. 377-398.

______, 1959, Padre Island and the Laguna Madre Flats, coastal south Texas, 2nd Coastal Geog. Conf., Coastal Studies Institute, La. State Univ., pp. 103-151.

Foscue, B. J., 1933, Irrigation in the lower Rio Grande Valley of Texas, Geog. Review, 23:457-463.

Foxworth., R. 0., et_ al. , 1962, Heavy minerals of sand from Recent beaches of the Gulf coast of Mississippi and associated rslands, Miss. Geol. Surv., Bull. 93.

Gilbert, G. K., 1885, The topographic features of lake shores, USGS, 5th Annual Report.

Goldstein, A., 1942, Sedimentary petrologic provinces of the northern Gulf of Mexico, J. Sed. Petrol., 12:77-84.

Goodell, H. G., and Gorsline, D. S., 1961, A sedimentologic study of Tampa Bay, Florida, Intern. Geol. Congr. Proc., 21st Session, Copenhagen, 23:75-88.

Gorsline, D. S., 1966, Dynamic characteristics of west Florida Gulf coast beaches, Marine Geol., 4:187-206. Gorsline, D. S., 1967, Contrasts in coastal bay sediments on the Gulf and Pacific coasts, in Estuaries (Ed., Lauff, G. II.), Airier. Assoc, for the Advancement of Science, pp. 219-225.

Gould, H. R. , and McFarlan, E., 1959, Geologic history of Chenier Plain, southwestern. Louisiana, Gulf Coast Assoc. Geol. Soc., Trans. 9:261-270.

_____ and Stewart, R. H., 1955, Continental terrace sediments in the northeastern Gulf of Mexico, in Finding Ancient Shorelines, Soc. Econ. Paleon. Min. Spec. Pub., Mo. 3, pp. 2-20.

Hails, J. R. , 1968, The late Quaternary history of part of the mid-north coast, Mew South Wales, Australia, Inst. British Geog., Trans. 44:133-149. •

Hayes, M. 0., and Scott, A. J., 1964, Environmental complexes, south Texas coast, Gulf Coast Assoc. Geol. Soc., Trans. 14:237-240.

Ho, C., and Meintire, W. G., Development of barrier island lagoons; western Gulf of Mexico, in press.

Hoyt, J. Ii. , 1967, Barrier island formation, Geol. Soc. Amer., Bull. 7S:1125-1136.

______1968, Barrier island formation; reply, Geol. Soc. Amer. Bull., 79:947.

Hsu, K. J., 1960, Texture and mineralogy of the Recent sands of the Gulf coast, J. Sed. Petrol., 30:380-403.

Hyne, N. J . , and Goodell, H. G., 1967, Origin of the sediments and submarine geomorphology of the inner continental shelf off Choctawhatch.ee Bay, Florida, Marine Geol., 5:299-313.

Johnson, D. W . , 1919, Shore processes and shoreline development, John Wiley & Sons, Inc., New York.

______, 1930, Offshore bars and eustatic changes of sea level, J. Geomorphology, 1:273-274.

Johnson, J. W., 1956, Dynamics of nearshore sediment movement, Amer, Assoc. Petrol. Geol., Bull. 40:2211-2232.

’ and Asce, M . , 1959, The supply and loss of sand to the coast, J. Waterways and Harbors Div., Amer. Soc. Civ. Eng., Proc. 85: 227-251.

Kamel, A. M. , 1962, Littoral studies near Saia Francisco using tracer techniques, Beach Erosion Board, Tech. Memo, No. 131.

Kane, II. E., 1959, Late Quaternary geology of Sabine Lake and vicinity, Texas and Louisiana, Gulf Coast Assoc. Geol. Soc., Trans. 9:225-235. 73

Kculcgan, G. H. , and Krumbein, W. C., 1942, Stable configuration of bottom slope in a shallow sea and its bearing on geological processesj Amer. Geophys. Union, Trans. 30:855-861.

Kofoed, J. W., and Gorsline, D. S., 1963, Sedimentary environments in Apalachicola Bay and vicinity, Florida, J. Sed. Petrol. , 33:205-225.

Kolb, C. R. , and Van Lopilc, J. R. , 1966, Deposition’al environments of the Mississippi River Deltaic plain - southeastern Louisiana, in Deltas (Ed., Shiriy, M. L., and Ragsdale, J. A.), Houston Geological Society, pp. 17-61.

Lankford, R. R., and Shepard, F. P., 1960, Facies interpretations in Mississippi Delta borings, J. Geol., '68:408-426.

LeBlanc, R. F., and Hodgson, W. D., 1959, Origin and development of the Texas shoreline, Gulf Coast Assoc. Geol. Soc., Trans. 9:197-220.

Leipper, D. F., 1954, Physical oceanography of the Gulf of Mexico, in Gulf of Mexico, Its Origin, Haters, and Marine Life, U.S. Dept. Interior, Fish and Wildlife Serv., Bull. 89:119-137.

Leontyev, 0. K . , 1965, On the cause of the present-day erosion of barrier bars, Coastal Research Notes, No.12, pp. 5-7.

______and Nikiforov, L. G., 1965, Reasons for the world-wide occurrence of barrier beaches, Oceanology, Vol. 5, No. 4, pp. 61-67.

______and Nikiforov, L. G., 1966, An approach to the problem of•the origin of barrier bars, 'Intern. Oceanographic Congr., 2nd, Abstr. of Papers, pp. 221-222.

Leverett, F., 1931, The pensacola terrace and associated beaches and bars in Florida, Fla. Geol. Surv., Bull. 7.

Lohse, E. A., 1955, Dynamic geology of the modern coastal region, north­ west Gulf of Mexico, in Finding Ancient Shorelines, Soc. Econ. Paleon. Min. Spec. Pub., No. 3, pp. 99-105.

______, 1958, Mouth of Rio Grande, in Sedimentology of south Texas (Field Trip' Guidebook), Gulf Coast Assoc.’ Geol. Soc., pp. 55-56.

Ludwick, J. C., 1964, Sediments in northeastern Gulf of Mexico, in Papers in Marine Geology (Ed., Miller, R. L), Macmillan Co., New York, pp. 204-235.

Lynch, S. A., 1954, Geology of the Gulf of Mexico, in Gulf of Mexico, Its Origin, Waters, and Marine Life, U.S. Dept. Interior, Fish and Wildlife Surv., Bull. 89:69-86.

Marmer, 11. A., 1954, Tides and sea level in the Gulf of Mexico, ill Gulf of Mexico, Its Origin, Waters, and Marine Life, U.S. Dept. Interior, Fish and Wildlife Serv., Bull. 89:101-118. Martens, J, H. C., 1931, Beaches of Florida, Fla. Geol. Surv., 22nd Annual Report, pp. 67-119.

McCroae, W. P., 1936, Gulf hurricanes and their effect on Texas shores and beaches, Shore and Beach, 24:23-27.

Mclntire, W. G., 1954, Correlation of prehistoric settlements and dclt development, La. State University, Tech. Rept. No. 5.

______and Morgan, J. P., 1962, Recent geomorphic history of Plum Islaiid, Massachusetts, and adjacent coasts, Coastal Studies Institute, La. State Univ., Tech. Rept. No. 19.

McMaster, R. L., 1934, Petrography and genesis of the New Jersey beach sands, New Jersey Geol. Serv., Bull. 63.

McNeil, F. S., 1950, Pleistocene shorelines in Florida and Georgia, USGS Prof. Paper 221-F, pp. 95-103.

Merrill, F. J. II., 1890, Barrier beaches of the Atlantic coast, Papula Sci. Monthly, 37:736-745.

Morgan, J. P., and Larimore, P. B., 1957, Changes in the Louisiana shoreline, Gulf Coast Assoc. Geol. Soc., Trans. 7:303-310.

' ____ and Treadwell, R. C., 1954, Cemented sandstone slabs of the Chandeleur Islands, Louisiana, J. Sed. Petrol., 24:71-75.

Myers, II. B., and Theis, A. R. , 1956,' Beach erosion control, Grand Isle, Louisiana, Shore and Beach, 24:19-23.

Norris, R. M., 1964, Dams and beach sand supply in southern California in Papers in Marine Geology '(Ed., Miller, R. II.), Macmillan Co., New York, pp. 154-171.

Patton, J. J., 1951, Beach erosion at Perdido Pass, Shore and Beach, 19:10-11.

Peyronnin, C. A., 1962, Erosion of Isles Dernieres and Timbalier Islands, J. Waterways and Harbors Div., Amer. Soc. Civ. Eng., Proc. 88:57-69.

Phleger, F. B., 1960, Sedimentary patterns of microfaunas in northern Gulf of Mexico, in Recent Seciments, northwest Gulf of Mexico (Ed., Shepard, F. P., et al.), Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma, pp. 267-301.

Potter, P. E., 1967, Sand bodies and sedimentary environments.; a review, Amer. Assoc. Petrol. Geol., Bull. 51:337-365.

Price, W. A., 1933, Role of diastrophism in topography of Corpus Christ! region, south. Texas, Amer. Assoc. Petrol. Geol., Bull. 17:907-962. Price, W. A., 1939, Offshore bars and eustatic changes of sea level: a reply, J. Geomorphology, 2:357-365.

_____ , 1947, Equilibrium of form and forces in tidal basins of coast of Texas and Louisiana, Amer. Assoc. Petrol. Geol., Bull. 31:1619-1663.

_____ , 1951, Barrier island, not "offshore bar," Science, 113:437-488.

______, 1954(a), Shorelines, and coasts of the Gulf of Mexico, in Gulf of Mexico, Its Origin, Waters, and Marine Life, U.S. Dept. Interior, Fish and Wildlife Surv., Bull. 89:39-62.

______, 1954(b), Dynamic environments: reconnaissance mapping, geologic and geomorphic, of continental shelf of Gulf of Mexico, Gulf Coast Assoc. Geol. Soc., Trans. 4:7-5-101.

______, 1956, Hurricanes affecting the coast of Texas from Galveston to Rio Gr'ande, Beach Erosion Board, Tech. Memo. No. 78.

_____ , 1958, Sedimentology and Quaternary geomorphology of south Texas, Gulf Coast Assoc. Geol. Soc., Trans. 8:41-75.

_____ , 1963, Origin of barrier chain and beach ridge (abstr.), Amer. Geol. Soc., Special Papers, 73:219.

______, and Gunter, G., 1943, Certain Recant geological and biological changes in south Texas with consideration of probable causes, Texas Acad. Sci. Proc., 26:138-156.

Priddy, R. R., and Smith, B. L., 1960, Recent sedimentation on Horn Island, Mississippi, Gulf Coast Assoc. Geol. Soc., Field Trips, pp. 5-8.

Puri, H. S., Hon, J. W., and Oglesb}*-,' W. R., 1967, Geology of Dixie and Gilchrist Counties, Florida, Fla. Geol. Surv., Bull. 49.

Rainwater, E. H . , 1964, Late Pleistocene and Recent history of Mississippi Sound between Beauvoir and Ship Island, Miss. Geol. Surv., Bull. 102:32-61.

Richmond, E. A., 1962, The fauna and flora of Horn Island, Mississippi, Gulf Research Reports, Vol. 1, No. 2.

Rogers, J. J. W . , and Adams, H. C., 1959, The mineralogy and texture of beach sands of Galveston Island, Texas, J. Sad. Petrol., 29:201-211.

Rusnalc, G. A., 1960, Sediments of Laguna Madre, Texas, in Recent Sediments, Northwest Gulf of Mexico (Ed., Shepard, F. P., et_ al.), Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma, pp. 153-196. 76

Russell, R. J., 1936, Physiography of the Lower Mississippi River Delta, La. Geol. Surv., Bull. 8:3-199.

______, 1938, Mississippi River Delta sedimentation, in Recent Marine Sediments, Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma, pp. 153- 177.

______, 1948,.Coast of Louisiana, Soc. Beige, de Geol., de Paleontol., et d ’ Hydrologic, Bull. 57:380-394.

______, 1957, Instability of sea level, Amer. Scientist, 45:414-430.

______, 1959, Background for field excursions, 2nd Coastal Geog. Conf., Coastal Studies Inst., La. State Univ., pp. 363-383.

______, 1967, Origins of estuaries-, in Estuaries (Ed., Lauff, G. R.), Amer. Assoc, for the Advancement of Science, pp. 93-99.

______, 1967, Aspects of coastal morphology, Geografiska Annaler, 49:299-309.

______1968, Glossary of terms used in fluvial, deltaic, and coastal morphology and processes, Coastal Studies Institute, La. State Univ., Tech. Rept. No. 63.

Shaler, N. S., 1871, On the causes which have led to the production of Cape Hatteras, Boston Soc. Natural History, Proc. 14:110-123.

Shepard, F. P., 1952, Revised nomenclature for depositional coastal features, Amer. Assoc. Petrol. Geol., Bull. 36:1902-1912.

, 1960, Gulf coast barriers, in Recent Sediments, Northwest Gulf of Mexico (Ed., Shepard, F. P., et al.), Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma, pp. 197-220.

____ , 1960, Rise of sea level along northwest Gulf of Mexico, in Recent Sediments, Northwest Gulf of Mexico (Ed., Shepard, F. P., 'et al.), Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma, pp. 338-344.

______, Inman, D. L., and Fisher, R. L., 1951, Marine beaches of the United States, Amer. Geol. Soc., Bull. 62:1477-1478.

, and Moore, D. G., 1955, Central Texas coast sedimentation: characteristics of sedimentary environment, Recent history, and diagenesis, Amer. Assoc. Petrol. Geol., Bull. 39:1463-1593.

Stewart, R. A., and Gorsline, D. S., 1962, Recent sedimentary history of St. Joseph Bay, Florida, Sedimentology, 1:256-286.

Swift, D. J. P., 1968, Coastal erosion and transgressive stratigraphy, J. Geol., 76:444-456. Taney, N. E. , 1961, Geomorphology of the south shore of Long Island, New York, B.each Erosion Board, Tech. Memo. No. 128.

Tanner, W. F., 1959, Near-shore studies in sedimentology and inorphoiogy along the Florida panhandle coast, J. Sed. Petrol., 29:564-574.

______> 1960(a), Perched barrier islands, east Florida coast, South­ eastern Geology, 2:133-135.

______, 1960(b), Expanding shoals in aread of wave refraction, Sci. , 132:1012-1013.

______, 1960(c), Florida coastal classification, Gulf Coast Assoc. Geol. Soc., Trans. 10:259-266.

_____ , 1961, Offshore shoals in area of energy deficit, J. Sed. Petrol., 31:87-95.

______, 1964, Nearly ideal drift system along the Florida panhandle coast, Zeit. fur Geom., S:334-342.

______, 1966, Late Cenoaoic history and coastal morphology of the Apalachicola River region, western Florida, in Deltas (Ed., Shirley, M. L., and Ragsdale, J. A.), Houston Geological Soc., pp. 83-97.

______, Evans, R. G., and Holmes, C. W . , 1963, Low-energy coast near Cape Romano, Florida, J. Sed. Petrol., 33:713-722.

Thornthwaite, C. W., 194S, An approach toward a rational classifica­ tion of climate, Geog. Review, 38:55-94.

Treadwell, R. C., 1955, Sedimentology and ecology of southeast coastal Louisiana, Coastal Studies Institute, La. State Univ., Tech. •Report No. 6.

Trowbridge, A. C., 1932, Tertiary and Quaternary geology of the lower Rio Grande region, Texas, USGS, Bull. 837.

Troxler, C. P., 1959, Beach erosion and shore-protectionsproblems and projects in Florida, Shore and Beach, 27:27-31.

Upshaw, C. F., et al., 1966, Sediments and microfauna off the coasts of Mississippi and adjacent states, Miss. Geol. Surv., Bull. 106.

U.S. Army Corps of Engineers, 1895, Survey of east end of Galveston Islax-id, Texas, U.S. Congress, House Doc. 64, 54th Congr. 1st Session.

_, 1953, Gulf shore of Galvaston Island, Texas: beach erosion control study, U.S. Congress, House Doc. 218, 83rd Congr., 1st Session. U.S. Army Corps of Engineers, 1954, Pinellas County, Florida, U.S. Congress, House Doc. 330, 83rd Congr., 2nd session.

______1955, Perdido Pass (Alabama Point), Alabama: beach erosion control study, U.S. Congress, House Doc. 274, 84th Congr., 2nd session.

______, 1957, Matagorda Ship Channel, Texas, U.S. Congress, House Doc. 3S8, S4th Congr., 2nd session.

______, 195S, Galveston Harbor and Channel, Houston Ship Channel and Texas City Channel, Texas, U.S. Congress, House Doc. 350, 85th Congr., 2nd session.

U.S. Geological Survey, Surface water supply of the U.S.,. 1959, G.S. Water-Supply Paper 1623 and 1632..

Van Andel, T. H., 1960, Holocene sediments, northern Gulf of Mexico, in Recent Sediments, Northwest Gulf of Mexico (Ed., Shepard, F. P., et al.), Amer. Assoc. Petrol. Geol., Tulsa, Oklahomh, pp. 34-55.

Vause, J. E., 1959, Underwater geology and analysis of Recent sediments off the northwest Florida coast, J. Sed. Petrol., 29:555-563.

Wadsworth, A. H., 1966, Historical deltation of the Colorado River, Texas, in Deltas (Ed., Shirley, M. L., and Ragsdale, J. A.), Houston Geological Soc., pp. 99-105.

Walton, W. R., 1960, Diagnostic faunal characteristics, on and near a barrier island, Horn Island, Mississippi, Gulf Coast Assoc. Geol. Soc., Trans. 10:7-24.

____ , 1963, Ecology of bentllonic foraminifera in the Tampa-Sarasota Eav area, Florida, in Papers in Marine Geology (Ed., Miller, R. L.), Macmillan Co., New York, pp. 429-454.

Weeks, A. W . , 1945, Quaternary deposits of Texas coastal plain between Brazos River and Rio Grande, Amer. Assoc. Petrol. Geol., Bull. 29:1693-1720.

Weidie, A. E., 1969, Bar and barrier island sands, Gulf Coast Assoc. Geol. Soc., Trans. 18:405-415.

Wilson, W. K., 1951,.Beach erosion problems in the'Mobile District, Shore and Beach, 19:8-10.

Zenkovich, V. P., 1962, Some new exploration results about sand shore development during the sea transgression, Ingenieur (Utrecht), 75(43):113-121.

_____ , 1964, Formation and burial of accumulation forms in littoral and near-shore marine environments, Marine Geology, 1:175-180. 79

Zenkovich, 1967, Processes of coastal development, Ed., J. A. Steers, John Wiley and Sons, Inc., New Yorlc. VITA

Hyuck Jac Kwon was born on December 29, 1936, at Gangnung,

Korea. He graduated from Dae Kwang 1-Iigi. v. .ool, Seoul, Korea, in

February of 1956 and entered the Seoul National University in

March of the same year. He received a Bachelor of Arts degree from the Department of Geography in March, 1960. lie taught geography at several high schools in Seoul until the.summer of

1965, when he came to the United States to engage in advanced study in geography at Louisiana State University. In September,

1965, he enrolled in the Graduate School in the Department of

Geography and Anthropology and worked toward a Master of Science degree in physical geography. He received the degree in May,

1967, and continued to work toward a doctorate in the same depart­ ment. Ills association with the Coastal Studies Institute began in September, 1967. He is now a candidate for the degree of

Doctor of Philosophy. EXAMINATION AND THESIS REPORT

Candidate: Hyuck Jae Kwon

Major Field: Geography

Title of Thesis: Source of Barrier Island Sediments: Northern Gulf Coast

Approved:

Major Professor and Chairman

Dean of the Graduate School

EXAMINING COMMITTEE:

—

Date of Examination:

May 14, 1969