28H: CHATHAM 11, GGS-1393
CHATHAM COUNTY, GEORGIA
7½’ Quadrangle
By
Paul F. Huddlestun
Originally Logged 1973
Relogged March, 1992
Written Up 98/Jan/2010
Reviewed by Huddleston Feb, 2024
Posted Here, 16/April/2024
Type section of the Lazaretto Creek Formation
The location of the core is on Tybee Island. adjacent to Catalina Drive, 0.7 miles south of the junction of Catalina Drive and US 80, approximately 1.25 miles due west of Savannah Beach
Latitude N 32° 00.375’
Longitude W 81° 51.980’
Elevation Less than 5 Feet
The location of the core is on Tybee Island. adjacent to Catalina Drive, 0.7 miles south of the junction of Catalina Drive and US 80, approximately 1.25 miles due west of Savannah Beach
Latitude N 32° 00.375’
Longitude W 81° 51.980’
Elevation Less than 5 Feet
Lithostratigraphic unit and bed number
Description Thickness Depth
NO CORE 45.0Ft 0.0Ft
CORE LOST IN CORE RUN? 15.0 45.0
CORE GAP 11.0 60.0
UPPER PLIESTOCENE
SATILLA FORMATION? – 11.5 feet+
Savannah River QAL?
Description Thickness Depth
NO CORE 45.0Ft 0.0Ft
CORE LOST IN CORE RUN? 15.0 45.0
CORE GAP 11.0 60.0
UPPER PLIESTOCENE
SATILLA FORMATION? – 11.5 feet+
Savannah River QAL?
Bed 1 Clay: finely sandy and micaceous; massive 6.5 71.0
and structureless; tough and hard when dry,
soft, sticky, and plastic when moist;
competency unknown due to overlying core
gap; grades downward into:
Bed 2 Sand: fine to coarse grained and poorly sorted; 1.5 77.5
pebbly, appears kaolinitic; massive and
structureless; brittle and friable when dry;
similar competency to overlying bed;
disconformably overlies:
and structureless; tough and hard when dry,
soft, sticky, and plastic when moist;
competency unknown due to overlying core
gap; grades downward into:
Bed 2 Sand: fine to coarse grained and poorly sorted; 1.5 77.5
pebbly, appears kaolinitic; massive and
structureless; brittle and friable when dry;
similar competency to overlying bed;
disconformably overlies:
MIDDLE MIOCENE, SERRAVALLIAN
HAWTHORNE GROUP
COOSAWHATCHIE FORMATION
Tybee Phosphorite Member – 21.5 feet
Bed 3 Phosphorite matrix: finely sandy and 3.0 79.0
argillaceous; massive and structureless;
unconsolidated but firm, moderately
coherent and competent; abruptly overlies:
Bed 4 Clay: (Berryville-type clay), slightly and finely 1.5 82.0
sandy and silty, phosphatic and burrowed
with vertical burrows; massive and
structureless; tough, firm and coherent;
olive-colored; abruptly overlies:
Bed 5 Phosphorite: sandy, argillaceous, and 17.0 83.5
slightly dolomitic with scattered small
vertebrate debris; massive and structureless;
unconsolidated but firm and coherent
(one core tube missing from ~85 feet to ~95
feet), known core recovery is 38%;
disconformably overlies:
HAWTHORNE GROUP
COOSAWHATCHIE FORMATION
Tybee Phosphorite Member – 21.5 feet
Bed 3 Phosphorite matrix: finely sandy and 3.0 79.0
argillaceous; massive and structureless;
unconsolidated but firm, moderately
coherent and competent; abruptly overlies:
Bed 4 Clay: (Berryville-type clay), slightly and finely 1.5 82.0
sandy and silty, phosphatic and burrowed
with vertical burrows; massive and
structureless; tough, firm and coherent;
olive-colored; abruptly overlies:
Bed 5 Phosphorite: sandy, argillaceous, and 17.0 83.5
slightly dolomitic with scattered small
vertebrate debris; massive and structureless;
unconsolidated but firm and coherent
(one core tube missing from ~85 feet to ~95
feet), known core recovery is 38%;
disconformably overlies:
LOWER MIOCENE, BURDIGALIAN
HAWTHORNE GROUP
MARKS HEAD FORMATION – 25.5 feet
Bed 6 Sand: fine to medium grained and 4.5 100.5
moderately sorted; somewhat argillaceous
and dolomitic, burrowed; massive and
structureless; unconsolidated but firm
and coherent; overlies core gap:
CORE GAP 2.5 105.0
Bed 7 Clay (fullers earth): slightly and finely sandy 18.5 107.5
and silty, somewhat phosphatic, a 1 foot
layer of argillaceous, phosphatic sand occurs
at the base of bed; massive and structureless;
tough, firm and very competent; abruptly and
disconformably overlies;
HAWTHORNE GROUP
MARKS HEAD FORMATION – 25.5 feet
Bed 6 Sand: fine to medium grained and 4.5 100.5
moderately sorted; somewhat argillaceous
and dolomitic, burrowed; massive and
structureless; unconsolidated but firm
and coherent; overlies core gap:
CORE GAP 2.5 105.0
Bed 7 Clay (fullers earth): slightly and finely sandy 18.5 107.5
and silty, somewhat phosphatic, a 1 foot
layer of argillaceous, phosphatic sand occurs
at the base of bed; massive and structureless;
tough, firm and very competent; abruptly and
disconformably overlies;
LOWER OLIGOCENE, VICKSBURGIAN
LAZARETTO CREEK FORMATION – 70 feet
Suwannee-equivalent
Bed 8 Limestone: sandy; massive and 12.5 126.0
structureless; soft but recovered core is
moderately indurated; either barely
coherent or hard/soft; poorly competent
(~28% core recovery); grades downward
into:
Bed 9 Limestone: sandy and moldic; sediment 26.5 138.5
recovered is massive and structureless;
mostly soft and unconsolidated; poorly
coherent (~13% recovery); overlies core
gap:
CORE GAP 13.5 151.5
Bed 10 Limestone: sandy; massive and structure- 31.0 165.0
less; unconsolidated and soft but more
coherent and competent than overlying
beds, core gaps from 172 feet to 183 feet;
(~65% core recovery); abruptly and
disconformably overlies:
LAZARETTO CREEK FORMATION – 70 feet
Suwannee-equivalent
Bed 8 Limestone: sandy; massive and 12.5 126.0
structureless; soft but recovered core is
moderately indurated; either barely
coherent or hard/soft; poorly competent
(~28% core recovery); grades downward
into:
Bed 9 Limestone: sandy and moldic; sediment 26.5 138.5
recovered is massive and structureless;
mostly soft and unconsolidated; poorly
coherent (~13% recovery); overlies core
gap:
CORE GAP 13.5 151.5
Bed 10 Limestone: sandy; massive and structure- 31.0 165.0
less; unconsolidated and soft but more
coherent and competent than overlying
beds, core gaps from 172 feet to 183 feet;
(~65% core recovery); abruptly and
disconformably overlies:
UPPER EOCENE, UPPER JACKSONIAN
OCALA GROUP
BYROZOAN-RICH LIMESTONE
Crystal River-equivalent – 6 feet+
Bed 11 Limestone: fossiliferous, no other lithic 4.5 196.0
components apparent; variably thin and
medium bedded; mostly indurated and hard;
Operculinoides and Aequipecten spillmanni
present; overlies core gap:
CORE GAP 1.5 200.5
TOTAL DEPTH – 202 FEET
OCALA GROUP
BYROZOAN-RICH LIMESTONE
Crystal River-equivalent – 6 feet+
Bed 11 Limestone: fossiliferous, no other lithic 4.5 196.0
components apparent; variably thin and
medium bedded; mostly indurated and hard;
Operculinoides and Aequipecten spillmanni
present; overlies core gap:
CORE GAP 1.5 200.5
TOTAL DEPTH – 202 FEET
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