The geology of the Monette area along the St. Francis River is that of a
complex river valley. It is further complicated by the New Madrid
earthquake of 1812 and perhaps some earlier disturbances of the same
nature.
On a substratum of undifferentiated plio-miocene deposits, the
cross-sectional profile of the valley (Fisk 1944, Plate 15, Sheet 1)
shows an elevation of 100 to 125 feet above the present mean sea level
as the base of the alluvial deposit. The top of this extensive
graveliferous alluvium, 225 feet above sea level, was laid down by the
Ohio River as its channel pattern changed through the centuries, burying
older channels under later ones as the ocean levels rose and the ice age
melted out of existence, thus forming the area known as the Malden
Plain. The present surface contour at the town of Monette is 235 feet.
At the site under study the elevation readings are from 237 to 240 feet
above sea level.
[Illustration: Figure 2. Aerial View of the St. Francis River
“Sunken Lands” and the Lawhorn Site
_(In circle)_]
[Illustration: Figure 3. Aerial View of Drainage Ditch and Levee at
the Lawhorn Site.
_(To the left of the levee is the St. Francis River in its present
“Sunken Lands” channel. The site limits are shown by a dotted
line)_]
[Illustration: Figure 4. Contour Map of the Lawhorn Site Showing
Levee, Drainage Ditch, Excavated Areas and Grid Control System]
This valley story is duplicated west of the area known locally as
Crowley’s Ridge where the Mississippi River flowed during the waning of
the ice age. Crowley’s Ridge, it should be noted here, is an old land
surface that was not eroded by the late glacial run-off waters. It is
this relatively unaltered ridge of land that originally separated the
Mississippi and Ohio Rivers during the formative age of the present
alluvial valley. This ridge, only a few miles west of Monette, Arkansas,
offered a totally different environment and was, presumably, one which
the Lawhorn people made, at least, seasonal use of. The St. Francis
River channel, lying close to the eastern edge of Crowley’s Ridge is the
end result of these early braided Ohio River channels while today the
Black River has replaced the Mississippi in the western valley.
By 2000 B.C. the Mississippi River had moved to the east side of
Crowley’s Ridge and well east of the Monette area. The Ohio River was
then in the vicinity of the present Mississippi River. During the next
1000 years the Mississippi channel moved gradually eastward until it was
flowing close to the Ohio River and roughly parallel to it, merging in
the vicinity of Helena, Arkansas. By the beginning of the Christian era,
the two rivers had joined near Cairo, Illinois and so began the modern
alluvial valley pattern (Fisk, 1944).
If the interpretation of the time of geological developments is correct
the story of mankind in this region would be limited to something less
than 6000 years. Early Man may have wandered the shoreline of the
ancient river channels, but if he did there is very little likelihood
that any of his remains would be found today in this valley area since
they would have been washed away or covered with the refilling of the
valley.
Further complicating the picture there has been a tremendous amount of
recent geological disturbance in this area due to the New Madrid
earthquake and possibly others of earlier date. These geological
developments set part of the environmental state for the users of the
Lawhorn site. Later developments contrived to destroy much of the
evidence left by man as a series of earthquakes changed the face of the
land (Humphries, 1960, p. 32).
Another factor that must be taken into account is the recent work of the
United States Army Engineers in protecting the higher lands from the
floods of the St. Francis River Sunken Lands and in draining this entire
region. Within the last five years a new ditch has been dug parallel to
a new levee on the east side so that it cut through a section of the
Lawhorn archaeological deposit. This work laid bare many skeletons and
considerable occupational debris. Harmful as this activity is to
archaeological sites it was nevertheless an important factor in bringing
this site to the attention of the writer. It is unfortunate that most
sites thus destroyed, in whole or in part, by drainage and levee
building excavations cannot be similarly salvaged. Governmental
machinery is available for this work but unfortunately there has been no
institutional agency ready, willing and able to accept the burden in
this area.
The first evidences of man at the Lawhorn site are sand tempered pottery
and associated dart points. These show that this site was occupied by
man long enough to produce an archaeological deposit judged to be
Woodland or Baytown. The deposit is thin and gives little evidence of
ever having been much deeper. Above this thin evidence were shell
tempered pottery and related stone, bone and shell artifacts that
indicated a more intensive use of the site at a later time by
Mississippian people.