LAKE TRAVELS WITH WALT: THE CARBON PUMP, CARBONATES, AND COON TAILS

Walt Dean was at heart a geochemist with a deep curiosity and appreciation for the beauty of banded sediments and their paleoenvironments. His work built a legacy of insights about lakes and the mysteries of their history revealed within the sediment record. With his background studying the Eocene Green River formation and marine sediment across geologic time (among many other localities), fostered by his advisor and then colleague and friend Roger Anderson, Walt Dean developed the seminal concept of the ‘carbon pump’ for carbonate lakes. I was one of many graduate students in the field of paleolimnology who was handed the Elk Lake GSA special volume and told to ‘read this and learn’. And like many, I subsequently sought out all his other papers on this topic in the late 1990’s and early 2000’s when I began to study the striking light and dark banding of my sediment records, which I later learned Walt affectionately referred to as ‘coon tails’. His Loss on Ignition method, published in 1974, and the resulting data he obtained from lake sediments revealed relationships that he pondered with his colleagues and friends. His critical insight, and one of his major contributions to field of paleolimnology, was how the balance between biological productivity, as reflected by organic matter and inorganic carbonate production within a lake, related to the factors that control carbonate dissolution and preservation in the sediment record. With the benefit of this knowledge, subsequent generations of paleolimnologists have built further upon the foundation of Walt’s work. This talk will present the fundamental concepts of Walt Dean’s ‘carbon pump’ with case studies that illustrate its power to unlock secrets of the sediment record.